diff --git a/web/src/components/plants/DeleteSeedLotModal.tsx b/web/src/components/plants/DeleteSeedLotModal.tsx
new file mode 100644
index 0000000..5d7dc00
--- /dev/null
+++ b/web/src/components/plants/DeleteSeedLotModal.tsx
@@ -0,0 +1,50 @@
+import { useState } from 'react'
+import { Alert } from '@/components/ui/Alert'
+import { Button } from '@/components/ui/Button'
+import { Modal } from '@/components/ui/Modal'
+import { errorMessage } from '@/lib/api'
+import { formatQuantity, useDeleteSeedLot, type SeedLot } from '@/lib/seedLots'
+
+/**
+ * Retire a lot. Worth confirming because it's the one place cost and germination
+ * data lives — and worth saying plainly that the plantings survive it, since
+ * "will this wipe my garden" is the reasonable fear.
+ */
+export function DeleteSeedLotModal({ lot, onClose }: { lot: SeedLot; onClose: () => void }) {
+  const del = useDeleteSeedLot()
+  const [error, setError] = useState<string | null>(null)
+
+  return (
+    <Modal title="Retire this seed lot?" onClose={onClose} busy={del.isPending}>
+      <div className="flex flex-col gap-3">
+        <p className="text-sm text-fg">
+          {formatQuantity(lot.quantity)} {lot.unit}
+          {lot.vendor ? ` from ${lot.vendor}` : ''}
+          {lot.packedForYear != null ? `, packed for ${lot.packedForYear}` : ''}.
+        </p>
+        <p className="text-sm text-muted">
+          Anything planted from it stays exactly where it is — it just stops being attributed to this purchase.
+        </p>
+        {error && <Alert>{error}</Alert>}
+        <div className="mt-1 flex justify-end gap-2">
+          <Button type="button" variant="ghost" onClick={onClose} disabled={del.isPending}>
+            Cancel
+          </Button>
+          <Button
+            type="button"
+            variant="danger"
+            disabled={del.isPending}
+            onClick={() =>
+              del.mutate(lot.id, {
+                onSuccess: onClose,
+                onError: (err) => setError(errorMessage(err, 'Could not retire the lot.')),
+              })
+            }
+          >
+            {del.isPending ? 'Retiring…' : 'Retire lot'}
+          </Button>
+        </div>
+      </div>
+    </Modal>
+  )
+}
diff --git a/web/src/components/plants/PlantCard.tsx b/web/src/components/plants/PlantCard.tsx
index fe56d6b..2a8d771 100644
--- a/web/src/components/plants/PlantCard.tsx
+++ b/web/src/components/plants/PlantCard.tsx
@@ -1,6 +1,10 @@
+import { useState } from 'react'
 import { PlantIcon } from './PlantIcon'
+import { LotStateChip, SeedLotList } from './SeedLotList'
+import { SourceLink } from './SourceLink'
 import { cardActionClass, cardDangerClass } from '@/components/ui/cardActions'
 import { CATEGORY_LABELS, isBuiltin, type Plant } from '@/lib/plants'
+import { formatQuantity, summarizeLots, type SeedLot } from '@/lib/seedLots'
 import { formatSpacing, type UnitPref } from '@/lib/units'
 
 /**
@@ -11,17 +15,30 @@ import { formatSpacing, type UnitPref } from '@/lib/units'
 export function PlantCard({
   plant,
   unit,
+  lots,
   onEdit,
   onDelete,
   onDuplicate,
+  onAddLot,
+  onEditLot,
+  onDeleteLot,
 }: {
   plant: Plant
   unit: UnitPref
+  /** This plant's purchases. A lot may reference a built-in, so even a built-in
+   *  card can carry seed. */
+  lots: SeedLot[]
   onEdit: () => void
   onDelete: () => void
   onDuplicate: () => void
+  onAddLot: () => void
+  onEditLot: (lot: SeedLot) => void
+  onDeleteLot: (lot: SeedLot) => void
 }) {
   const builtin = isBuiltin(plant)
+  const [showLots, setShowLots] = useState(false)
+  const summary = summarizeLots(lots)
+
   return (
     <div className="flex flex-col rounded-xl border border-border bg-surface">
       <div className="flex items-start gap-3 p-4">
@@ -38,6 +55,12 @@ export function PlantCard({
           <p className="mt-0.5 text-sm text-muted">
             {CATEGORY_LABELS[plant.category]} · {formatSpacing(plant.spacingCm, unit)} spacing
           </p>
+          {(plant.vendor || plant.sourceUrl) && (
+            <p className="mt-0.5 flex flex-wrap items-center gap-1.5 text-xs text-muted">
+              {plant.vendor && <span>{plant.vendor}</span>}
+              <SourceLink url={plant.sourceUrl} />
+            </p>
+          )}
           {plant.notes && <p className="mt-1 line-clamp-2 text-xs text-muted">{plant.notes}</p>}
         </div>
         <span
@@ -46,7 +69,34 @@ export function PlantCard({
           title={plant.color}
         />
       </div>
-      <div className="flex justify-end gap-1 border-t border-border px-2 py-1.5">
+      {showLots && (
+        <div className="border-t border-border px-3 py-2">
+          <SeedLotList lots={lots} canEdit onAdd={onAddLot} onEdit={onEditLot} onDelete={onDeleteLot} />
+        </div>
+      )}
+
+      <div className="flex items-center justify-end gap-1 border-t border-border px-2 py-1.5">
+        {/* The seed count sits with the actions rather than in the body: it's
+            what you scan for down a list of twenty packets, so it wants a fixed
+            place on the card. */}
+        <button
+          type="button"
+          onClick={() => setShowLots((v) => !v)}
+          className={`${cardActionClass} mr-auto flex items-center gap-1.5`}
+          aria-expanded={showLots}
+        >
+          {lots.length === 0 ? (
+            <span className="text-muted">No seed</span>
+          ) : (
+            <>
+              <span className="tabular-nums">
+                {formatQuantity(summary.remaining)}
+                {summary.unit ? ` ${summary.unit}` : ''} left
+              </span>
+              <LotStateChip state={summary.state} />
+            </>
+          )}
+        </button>
         <button type="button" onClick={onDuplicate} className={cardActionClass}>
           Duplicate
         </button>
diff --git a/web/src/components/plants/PlantFormModal.tsx b/web/src/components/plants/PlantFormModal.tsx
index 70faae3..2072617 100644
--- a/web/src/components/plants/PlantFormModal.tsx
+++ b/web/src/components/plants/PlantFormModal.tsx
@@ -16,6 +16,7 @@ import {
   type PlantCategory,
   type PlantInput,
 } from '@/lib/plants'
+import { safeExternalUrl } from '@/lib/seedLots'
 import { cmFromSpacing, spacingFromCm, spacingUnitLabel, type UnitPref } from '@/lib/units'
 
 const DEFAULT_COLOR = '#4a7c3f'
@@ -61,6 +62,8 @@ export function PlantFormModal({
   const [color, setColor] = useState(expandHex(source?.color ?? DEFAULT_COLOR))
   const [icon, setIcon] = useState(source?.icon ?? DEFAULT_ICON)
   const [days, setDays] = useState(source?.daysToMaturity != null ? String(source.daysToMaturity) : '')
+  const [sourceUrl, setSourceUrl] = useState(source?.sourceUrl ?? '')
+  const [vendor, setVendor] = useState(source?.vendor ?? '')
   const [notes, setNotes] = useState(source?.notes ?? '')
   const [version, setVersion] = useState(plant?.version ?? 0)
   const [conflict, setConflict] = useState<string | null>(null)
@@ -96,6 +99,14 @@ export function PlantFormModal({
       daysToMaturity = d
     }
 
+    // The server refuses anything that isn't http(s) with a host, but say so here
+    // rather than letting a paste of "johnnyseeds.com" come back as a generic
+    // error with no hint about which field or why.
+    if (sourceUrl.trim() && !safeExternalUrl(sourceUrl.trim())) {
+      setFormError('The source link needs to be a full http:// or https:// address.')
+      return
+    }
+
     const input: PlantInput = {
       name: name.trim(),
       category,
@@ -103,6 +114,8 @@ export function PlantFormModal({
       color,
       icon: icon.trim(),
       daysToMaturity,
+      sourceUrl: sourceUrl.trim(),
+      vendor: vendor.trim(),
       notes: notes.trim(),
     }
 
@@ -194,6 +207,27 @@ export function PlantFormModal({
           onChange={(e) => setDays(e.target.value)}
         />
 
+        {/* Provenance for the variety itself. What you bought and what's left
+            of it is a seed lot, added from the plant card. */}
+        <div className="grid grid-cols-2 gap-3">
+          <TextField
+            label="Vendor"
+            name="vendor"
+            placeholder="Johnny's Selected Seeds"
+            value={vendor}
+            onChange={(e) => setVendor(e.target.value)}
+          />
+          <TextField
+            label="Source link"
+            name="sourceUrl"
+            type="url"
+            inputMode="url"
+            placeholder="https://…"
+            value={sourceUrl}
+            onChange={(e) => setSourceUrl(e.target.value)}
+          />
+        </div>
+
         <TextArea label="Notes" name="notes" rows={2} value={notes} onChange={(e) => setNotes(e.target.value)} />
 
         {formError && <Alert>{formError}</Alert>}
diff --git a/web/src/components/plants/SeedLotList.tsx b/web/src/components/plants/SeedLotList.tsx
new file mode 100644
index 0000000..afff2c0
--- /dev/null
+++ b/web/src/components/plants/SeedLotList.tsx
@@ -0,0 +1,161 @@
+import { Button } from '@/components/ui/Button'
+import { cn } from '@/lib/cn'
+import { SourceLink } from './SourceLink'
+import {
+  formatCost,
+  formatQuantity,
+  formatUnitCost,
+  lotState,
+  type LotState,
+  type SeedLot,
+} from '@/lib/seedLots'
+
+const STATE_LABEL: Record<LotState, string> = {
+  over: 'over-planted',
+  empty: 'empty',
+  low: 'low',
+  ok: 'in stock',
+  unknown: 'no count',
+}
+
+// Encoded in colour AND words, because this is the thing you skim down a list of
+// twenty packets deciding what to order — a bare number doesn't survive that.
+const STATE_CLASS: Record<LotState, string> = {
+  // "over" is a discrepancy to look at rather than a shortage to act on, so it
+  // reads as a distinct warning rather than sharing "low"'s styling.
+  over: 'bg-orange-500/25 text-orange-900 dark:text-orange-200',
+  empty: 'bg-red-500/15 text-red-800 dark:text-red-300',
+  low: 'bg-amber-500/20 text-amber-800 dark:text-amber-300',
+  ok: 'bg-accent/20 text-accent-strong',
+  unknown: 'bg-border/60 text-muted',
+}
+
+export function LotStateChip({ state, className }: { state: LotState; className?: string }) {
+  return (
+    <span
+      className={cn(
+        'shrink-0 rounded px-1.5 py-0.5 text-[10px] font-medium uppercase tracking-wide',
+        STATE_CLASS[state],
+        className,
+      )}
+    >
+      {STATE_LABEL[state]}
+    </span>
+  )
+}
+
+/** A proportional bar for how much of a lot is left, so the state reads before
+ *  any of the text does. Omitted when there's no quantity to be a fraction of. */
+function RemainingBar({ lot }: { lot: SeedLot }) {
+  if (lot.quantity <= 0) return null
+  const pct = Math.max(0, Math.min(100, (lot.remaining / lot.quantity) * 100))
+  const state = lotState(lot)
+  return (
+    <div className="mt-1 h-1 w-full overflow-hidden rounded-full bg-border/60">
+      <div
+        className={cn(
+          'h-full rounded-full',
+          state === 'ok' ? 'bg-accent' : state === 'low' ? 'bg-amber-500' : 'bg-red-500',
+        )}
+        style={{ width: `${pct}%` }}
+      />
+    </div>
+  )
+}
+
+/**
+ * A plant's purchases: what came from where, and what's left of each.
+ *
+ * Two lots of the same variety are two separate rows with independent counts,
+ * which is the whole reason inventory lives on the purchase rather than on the
+ * plant (#50).
+ */
+export function SeedLotList({
+  lots,
+  canEdit,
+  onAdd,
+  onEdit,
+  onDelete,
+}: {
+  lots: SeedLot[]
+  canEdit: boolean
+  onAdd: () => void
+  onEdit: (lot: SeedLot) => void
+  onDelete: (lot: SeedLot) => void
+}) {
+  return (
+    <div className="flex flex-col gap-2">
+      {lots.length === 0 && (
+        <p className="text-xs text-muted">
+          No seed recorded. Add a lot to track what you bought and how much is left.
+        </p>
+      )}
+      {lots.map((lot) => (
+        <LotRow key={lot.id} lot={lot} canEdit={canEdit} onEdit={() => onEdit(lot)} onDelete={() => onDelete(lot)} />
+      ))}
+      {canEdit && (
+        <Button variant="ghost" className="self-start px-2 py-1 text-xs" onClick={onAdd}>
+          + Add seed lot
+        </Button>
+      )}
+    </div>
+  )
+}
+
+function LotRow({
+  lot,
+  canEdit,
+  onEdit,
+  onDelete,
+}: {
+  lot: SeedLot
+  canEdit: boolean
+  onEdit: () => void
+  onDelete: () => void
+}) {
+  const cost = formatCost(lot.costCents)
+  const unitCost = formatUnitCost(lot)
+
+  return (
+    <div className="rounded-lg border border-border px-2 py-1.5">
+      <div className="flex items-start gap-2">
+        <div className="min-w-0 flex-1">
+          <p className="flex flex-wrap items-center gap-1.5 text-sm text-fg">
+            <span className="font-medium tabular-nums">
+              {formatQuantity(lot.remaining)} / {formatQuantity(lot.quantity)} {lot.unit}
+            </span>
+            <LotStateChip state={lotState(lot)} />
+          </p>
+          <p className="mt-0.5 flex flex-wrap items-center gap-x-1.5 gap-y-0.5 text-xs text-muted">
+            {lot.vendor && <span>{lot.vendor}</span>}
+            {lot.packedForYear != null && <span>packed for {lot.packedForYear}</span>}
+            {lot.purchasedAt && <span>bought {lot.purchasedAt}</span>}
+            {lot.germinationPct != null && <span>{lot.germinationPct}% germ.</span>}
+            {cost && <span>{unitCost ? `${cost} (${unitCost})` : cost}</span>}
+            <SourceLink url={lot.sourceUrl} />
+          </p>
+          <RemainingBar lot={lot} />
+        </div>
+        {canEdit && (
+          <div className="flex shrink-0 flex-col items-end">
+            <button
+              type="button"
+              onClick={onEdit}
+              className="rounded px-1.5 py-0.5 text-xs text-muted outline-none hover:text-fg focus-visible:ring-2 focus-visible:ring-accent/40"
+            >
+              Edit
+            </button>
+            <button
+              type="button"
+              onClick={onDelete}
+              className="rounded px-1.5 py-0.5 text-xs text-red-700 outline-none hover:underline focus-visible:ring-2 focus-visible:ring-accent/40 dark:text-red-400"
+            >
+              Retire
+            </button>
+          </div>
+        )}
+      </div>
+      {lot.notes && <p className="mt-1 text-xs text-muted">{lot.notes}</p>}
+    </div>
+  )
+}
diff --git a/web/src/components/plants/SeedLotModal.tsx b/web/src/components/plants/SeedLotModal.tsx
new file mode 100644
index 0000000..84d2e09
--- /dev/null
+++ b/web/src/components/plants/SeedLotModal.tsx
@@ -0,0 +1,248 @@
+import { useState, type FormEvent } from 'react'
+import { Alert } from '@/components/ui/Alert'
+import { Button } from '@/components/ui/Button'
+import { Modal } from '@/components/ui/Modal'
+import { Select } from '@/components/ui/Select'
+import { TextArea } from '@/components/ui/TextArea'
+import { TextField } from '@/components/ui/TextField'
+import { errorMessage } from '@/lib/api'
+import {
+  conflictSeedLot,
+  LOT_UNITS,
+  safeExternalUrl,
+  useCreateSeedLot,
+  useUpdateSeedLot,
+  type LotUnit,
+  type SeedLot,
+} from '@/lib/seedLots'
+import type { Plant } from '@/lib/plants'
+
+/**
+ * Record a purchase, or correct one. Everything except quantity and unit is
+ * optional — the point is to make writing it down cheap enough to bother with,
+ * and a form that demands a SKU and a lot code gets skipped.
+ */
+export function SeedLotModal({
+  plant,
+  lot,
+  onClose,
+}: {
+  plant: Plant
+  /** Editing an existing lot, or undefined to record a new one. */
+  lot?: SeedLot
+  onClose: () => void
+}) {
+  const isEdit = !!lot
+  const create = useCreateSeedLot()
+  const update = useUpdateSeedLot()
+  const pending = create.isPending || update.isPending
+
+  // A new lot inherits the plant's vendor and source link, since the usual case
+  // is buying the variety you already recorded from the place you recorded it.
+  const [vendor, setVendor] = useState(lot?.vendor ?? plant.vendor ?? '')
+  const [sourceUrl, setSourceUrl] = useState(lot?.sourceUrl ?? plant.sourceUrl ?? '')
+  const [quantity, setQuantity] = useState(lot ? String(lot.quantity) : '')
+  const [unit, setUnit] = useState<LotUnit>(lot?.unit ?? 'seeds')
+  const [purchasedAt, setPurchasedAt] = useState(lot?.purchasedAt ?? '')
+  const [packedForYear, setPackedForYear] = useState(lot?.packedForYear != null ? String(lot.packedForYear) : '')
+  const [cost, setCost] = useState(lot?.costCents != null ? (lot.costCents / 100).toFixed(2) : '')
+  const [germination, setGermination] = useState(lot?.germinationPct != null ? String(lot.germinationPct) : '')
+  const [sku, setSku] = useState(lot?.sku ?? '')
+  const [lotCode, setLotCode] = useState(lot?.lotCode ?? '')
+  const [notes, setNotes] = useState(lot?.notes ?? '')
+  const [version, setVersion] = useState(lot?.version ?? 0)
+  const [conflict, setConflict] = useState<string | null>(null)
+  const [error, setError] = useState<string | null>(null)
+
+  async function onSubmit(e: FormEvent) {
+    e.preventDefault()
+    setError(null)
+    setConflict(null)
+
+    const qty = quantity.trim() === '' ? 0 : Number(quantity)
+    if (!Number.isFinite(qty) || qty < 0) {
+      setError('Quantity must be a number, or left blank.')
+      return
+    }
+    if (sourceUrl.trim() && !safeExternalUrl(sourceUrl.trim())) {
+      setError('The source link needs to be a full http:// or https:// address.')
+      return
+    }
+    let year: number | null = null
+    if (packedForYear.trim()) {
+      const y = Number(packedForYear)
+      if (!Number.isInteger(y) || y < 1900 || y > 2200) {
+        setError('Packed-for year should be a four-digit year.')
+        return
+      }
+      year = y
+    }
+    let costCents: number | null = null
+    if (cost.trim()) {
+      const c = Number(cost)
+      if (!Number.isFinite(c) || c < 0) {
+        setError('Cost must be an amount, or left blank.')
+        return
+      }
+      costCents = Math.round(c * 100)
+    }
+    let germinationPct: number | null = null
+    if (germination.trim()) {
+      const g = Number(germination)
+      if (!Number.isFinite(g) || g < 0 || g > 100) {
+        setError('Germination is a percentage between 0 and 100.')
+        return
+      }
+      germinationPct = g
+    }
+
+    const input = {
+      plantId: plant.id,
+      vendor: vendor.trim(),
+      sourceUrl: sourceUrl.trim(),
+      sku: sku.trim(),
+      lotCode: lotCode.trim(),
+      purchasedAt: purchasedAt.trim() === '' ? null : purchasedAt.trim(),
+      packedForYear: year,
+      quantity: qty,
+      unit,
+      costCents,
+      germinationPct,
+      notes: notes.trim(),
+    }
+
+    try {
+      if (isEdit) {
+        await update.mutateAsync({ id: lot.id, version, ...input })
+      } else {
+        await create.mutateAsync(input)
+      }
+      onClose()
+    } catch (err) {
+      const current = conflictSeedLot(err)
+      if (current) {
+        // Someone edited this lot elsewhere. Rebase onto the fresh row so a
+        // re-save applies, rather than making them retype everything — the same
+        // contract every other version-guarded form here honours.
+        setVersion(current.version)
+        setVendor(current.vendor)
+        setSourceUrl(current.sourceUrl)
+        setQuantity(String(current.quantity))
+        setUnit(current.unit)
+        setPurchasedAt(current.purchasedAt ?? '')
+        setPackedForYear(current.packedForYear != null ? String(current.packedForYear) : '')
+        setCost(current.costCents != null ? (current.costCents / 100).toFixed(2) : '')
+        setGermination(current.germinationPct != null ? String(current.germinationPct) : '')
+        setSku(current.sku)
+        setLotCode(current.lotCode)
+        setNotes(current.notes)
+        setConflict('This lot changed elsewhere. The latest values are shown — review and save again.')
+        return
+      }
+      setError(errorMessage(err, isEdit ? 'Could not save the lot.' : 'Could not record the lot.'))
+    }
+  }
+
+  return (
+    <Modal title={isEdit ? 'Edit seed lot' : `Seed lot — ${plant.name}`} onClose={onClose} busy={pending}>
+      <form onSubmit={onSubmit} className="flex flex-col gap-3">
+        {conflict && <Alert tone="info">{conflict}</Alert>}
+
+        <div className="grid grid-cols-2 gap-3">
+          <TextField
+            label="Quantity"
+            name="quantity"
+            type="number"
+            inputMode="decimal"
+            step="any"
+            min="0"
+            value={quantity}
+            onChange={(e) => setQuantity(e.target.value)}
+          />
+          <Select
+            label="Unit"
+            name="unit"
+            value={unit}
+            onChange={(e) => setUnit(e.target.value as LotUnit)}
+            options={LOT_UNITS.map((u) => ({ value: u.value, label: u.label }))}
+          />
+        </div>
+
+        <div className="grid grid-cols-2 gap-3">
+          <TextField label="Vendor" name="vendor" value={vendor} onChange={(e) => setVendor(e.target.value)} />
+          <TextField
+            label="Source link"
+            name="sourceUrl"
+            type="url"
+            inputMode="url"
+            placeholder="https://…"
+            value={sourceUrl}
+            onChange={(e) => setSourceUrl(e.target.value)}
+          />
+        </div>
+
+        <div className="grid grid-cols-2 gap-3">
+          <TextField
+            label="Purchased"
+            name="purchasedAt"
+            type="date"
+            value={purchasedAt}
+            onChange={(e) => setPurchasedAt(e.target.value)}
+          />
+          <TextField
+            label="Packed for"
+            name="packedForYear"
+            type="number"
+            inputMode="numeric"
+            placeholder="2026"
+            value={packedForYear}
+            onChange={(e) => setPackedForYear(e.target.value)}
+          />
+        </div>
+
+        <div className="grid grid-cols-2 gap-3">
+          <TextField
+            label="Cost"
+            name="cost"
+            type="number"
+            inputMode="decimal"
+            step="0.01"
+            min="0"
+            placeholder="4.99"
+            value={cost}
+            onChange={(e) => setCost(e.target.value)}
+          />
+          <TextField
+            label="Germination %"
+            name="germination"
+            type="number"
+            inputMode="decimal"
+            step="any"
+            min="0"
+            max="100"
+            value={germination}
+            onChange={(e) => setGermination(e.target.value)}
+          />
+        </div>
+
+        <div className="grid grid-cols-2 gap-3">
+          <TextField label="SKU" name="sku" value={sku} onChange={(e) => setSku(e.target.value)} />
+          <TextField label="Lot code" name="lotCode" value={lotCode} onChange={(e) => setLotCode(e.target.value)} />
+        </div>
+
+        <TextArea label="Notes" name="lotNotes" rows={2} value={notes} onChange={(e) => setNotes(e.target.value)} />
+
+        {error && <Alert>{error}</Alert>}
+
+        <div className="mt-1 flex justify-end gap-2">
+          <Button type="button" variant="ghost" onClick={onClose} disabled={pending}>
+            Cancel
+          </Button>
+          <Button type="submit" disabled={pending}>
+            {pending ? 'Saving…' : isEdit ? 'Save' : 'Record lot'}
+          </Button>
+        </div>
+      </form>
+    </Modal>
+  )
+}
diff --git a/web/src/components/plants/SourceLink.tsx b/web/src/components/plants/SourceLink.tsx
new file mode 100644
index 0000000..df92550
--- /dev/null
+++ b/web/src/components/plants/SourceLink.tsx
@@ -0,0 +1,27 @@
+import { safeExternalUrl } from '@/lib/seedLots'
+
+/**
+ * A link out to where seed came from.
+ *
+ * The href is a URL somebody pasted, so it is re-checked here before rendering
+ * and carries rel="noopener noreferrer" — the server scheme-checks it too (#50),
+ * but a link is rendered from whatever the client was handed, and "the backend
+ * validated it" is not a reason to hand javascript: to an anchor tag.
+ *
+ * Renders nothing at all when the URL is absent or unsafe, so callers don't each
+ * have to remember to guard.
+ */
+export function SourceLink({ url, label = 'source' }: { url: string; label?: string }) {
+  const safe = safeExternalUrl(url)
+  if (!safe) return null
+  return (
+    <a
+      href={safe}
+      target="_blank"
+      rel="noopener noreferrer"
+      className="underline decoration-dotted underline-offset-2 hover:text-fg"
+    >
+      {label} ↗
+    </a>
+  )
+}
diff --git a/web/src/editor/GardenCanvas.tsx b/web/src/editor/GardenCanvas.tsx
index c77bfc3..78ba6f1 100644
--- a/web/src/editor/GardenCanvas.tsx
+++ b/web/src/editor/GardenCanvas.tsx
@@ -96,6 +96,7 @@ export function GardenCanvas({
   const focusedObjectId = useEditorStore((s) => s.focusedObjectId)
   const setFocusedObject = useEditorStore((s) => s.setFocusedObject)
   const armedPlant = useEditorStore((s) => s.armedPlant)
+  const armedLotId = useEditorStore((s) => s.armedLotId)
   const liveObject = useEditorStore((s) => s.liveObject)
   const livePlanting = useEditorStore((s) => s.livePlanting)
   const { fitToRect } = useViewport(svgRef)
@@ -200,7 +201,14 @@ export function GardenCanvas({
     const radiusCm = Math.max(1.5 * armedPlant.spacingCm, 15)
     // Stay armed for repeat-placement; don't select (the placement sheet covers
     // the object, so a selection would be hidden until placement ends anyway).
-    createPlanting.mutate({ objectId: focusedObject.id, plantId: armedPlant.id, xCm: x, yCm: y, radiusCm })
+    createPlanting.mutate({
+      objectId: focusedObject.id,
+      plantId: armedPlant.id,
+      xCm: x,
+      yCm: y,
+      radiusCm,
+      seedLotId: armedLotId ?? undefined,
+    })
   }
 
   const halfFW = focusedObject ? focusedObject.widthCm / 2 : 0
diff --git a/web/src/editor/PlantPicker.tsx b/web/src/editor/PlantPicker.tsx
index 3e86f8c..8f2d5d7 100644
--- a/web/src/editor/PlantPicker.tsx
+++ b/web/src/editor/PlantPicker.tsx
@@ -4,6 +4,16 @@ import { fieldControlClass } from '@/components/ui/field'
 import { CategoryChips } from '@/components/plants/CategoryChips'
 import { PlantIcon } from '@/components/plants/PlantIcon'
 import { CATEGORY_LABELS, filterPlants, usePlants, type CategoryFilter, type Plant } from '@/lib/plants'
+import {
+  attributableLots,
+  formatQuantity,
+  lotsByPlant,
+  lotState,
+  summarizeLots,
+  useSeedLots,
+  type SeedLot,
+} from '@/lib/seedLots'
+import { LotStateChip } from '@/components/plants/SeedLotList'
 import { formatSpacing, type UnitPref } from '@/lib/units'
 
 const RECENT_KEY = 'pansy:recent-plants'
@@ -41,11 +51,20 @@ export function PlantPicker({
   onClose,
   unit = 'metric',
 }: {
-  onSelect: (plant: Plant) => void
+  // The chosen plant, and the lot it should be attributed to when that isn't
+  // ambiguous. Undefined lot means "don't attribute" — which is the honest
+  // answer when there are no lots, and the deliberate one when the user skips.
+  onSelect: (plant: Plant, lot?: SeedLot) => void
   onClose: () => void
   unit?: UnitPref
 }) {
   const plants = usePlants()
+  const seedLots = useSeedLots()
+  const lotsFor = useMemo(() => lotsByPlant(seedLots.data), [seedLots.data])
+  // Set when a plant with SEVERAL lots is picked: which packet did this come out
+  // of? One lot auto-attributes and zero lots stays silent, because forcing that
+  // question on every placement is how a nicety becomes an obstacle.
+  const [choosingLotFor, setChoosingLotFor] = useState<Plant | null>(null)
   const [query, setQuery] = useState('')
   const [category, setCategory] = useState<CategoryFilter>('all')
   const [recent, setRecent] = useState<number[]>(() => loadRecent())
@@ -74,8 +93,21 @@ export function PlantPicker({
   }, [all, recent, query])
 
   function choose(p: Plant) {
+    const lots = attributableLots(lotsFor.get(p.id) ?? [])
+    if (lots.length > 1) {
+      setChoosingLotFor(p)
+      return
+    }
     setRecent(recordRecent(p.id))
-    onSelect(p)
+    // A single lot attributes even when its count says empty. The count records
+    // what was written down, not a fact about the packet — dropping attribution
+    // there would make a wrong number harder to correct rather than easier.
+    onSelect(p, lots[0])
+  }
+
+  function chooseLot(p: Plant, lot?: SeedLot) {
+    setRecent(recordRecent(p.id))
+    onSelect(p, lot)
   }
 
   // A plant option row. keyPrefix namespaces the key so a plant appearing in
@@ -92,11 +124,22 @@ export function PlantPicker({
         <span className="block truncate font-medium text-fg">{p.name}</span>
         <span className="block text-xs text-muted">
           {CATEGORY_LABELS[p.category]} · {formatSpacing(p.spacingCm, unit)}
+          {remainingLabel(lotsFor.get(p.id) ?? [])}
         </span>
       </span>
     </button>
   )
 
+  // What's left, shown where you're deciding what to plant. Silent when there
+  // are no lots — most plants won't have any, and "0 left" on all of them would
+  // be noise that trains you to ignore the number. summarizeLots owns the
+  // unit-agreement rule; a second copy of it here would drift.
+  function remainingLabel(lots: SeedLot[]): string {
+    if (lots.length === 0) return ''
+    const { remaining, unit } = summarizeLots(lots)
+    return ` · ${formatQuantity(remaining)}${unit ? ` ${unit}` : ''} left`
+  }
+
   return (
     <div
       className="fixed inset-0 z-50 flex items-end justify-center bg-black/40 sm:items-center sm:p-4"
@@ -132,7 +175,41 @@ export function PlantPicker({
           <CategoryChips value={category} onChange={setCategory} size="sm" />
         </div>
 
-        <div className="min-h-0 flex-1 overflow-y-auto p-2">
+        {choosingLotFor && (
+          <div className="min-h-0 flex-1 overflow-y-auto p-2">
+            <p className="px-3 pb-1 pt-2 text-xs font-semibold uppercase tracking-wide text-muted">
+              Which lot of {choosingLotFor.name}?
+            </p>
+            {attributableLots(lotsFor.get(choosingLotFor.id) ?? []).map((lot) => (
+                <button
+                  key={lot.id}
+                  type="button"
+                  onClick={() => chooseLot(choosingLotFor, lot)}
+                  className="flex w-full items-center gap-3 rounded-lg px-3 py-2.5 text-left outline-none transition-colors hover:bg-border/50 focus-visible:bg-border/50"
+                >
+                  <span className="min-w-0 flex-1">
+                    <span className="block truncate text-sm font-medium text-fg">
+                      {lot.vendor || 'Unnamed lot'}
+                      {lot.packedForYear != null ? ` · ${lot.packedForYear}` : ''}
+                    </span>
+                    <span className="block text-xs text-muted">
+                      {formatQuantity(lot.remaining)} of {formatQuantity(lot.quantity)} {lot.unit} left
+                    </span>
+                  </span>
+                  <LotStateChip state={lotState(lot)} />
+                </button>
+            ))}
+            <button
+              type="button"
+              onClick={() => chooseLot(choosingLotFor, undefined)}
+              className="w-full rounded-lg px-3 py-2.5 text-left text-sm text-muted outline-none transition-colors hover:bg-border/50 focus-visible:bg-border/50"
+            >
+              Don't attribute to a lot
+            </button>
+          </div>
+        )}
+
+        <div className={cn('min-h-0 flex-1 overflow-y-auto p-2', choosingLotFor && 'hidden')}>
           {plants.isPending && <p className="p-4 text-sm text-muted">Loading plants…</p>}
           {plants.isError && <p className="p-4 text-sm text-red-600 dark:text-red-400">Couldn't load plants.</p>}
 
diff --git a/web/src/editor/store.ts b/web/src/editor/store.ts
index af1078a..1e55f97 100644
--- a/web/src/editor/store.ts
+++ b/web/src/editor/store.ts
@@ -47,7 +47,10 @@ interface EditorState {
   // The plant armed for placing plops (set after the PlantPicker choice); stays
   // armed for repeat-placement until cleared (Escape / done). null = not placing.
   armedPlant: Plant | null
-  setArmedPlant: (p: Plant | null) => void
+  // Which seed lot placements should be attributed to, when the armed plant has
+  // one worth naming. Cleared with the plant.
+  armedLotId: number | null
+  setArmedPlant: (p: Plant | null, lotId?: number | null) => void
 
   // During a move/resize/rotate, the object's live geometry is held here so the
   // canvas renders it instantly; the PATCH fires only on gesture end.
@@ -98,7 +101,8 @@ export const useEditorStore = create<EditorState>((set) => ({
   setJournalObjectId: (id) => set({ journalObjectId: id }),
 
   armedPlant: null,
-  setArmedPlant: (p) => set({ armedPlant: p }),
+  armedLotId: null,
+  setArmedPlant: (p, lotId = null) => set({ armedPlant: p, armedLotId: p ? lotId : null }),
 
   liveObject: null,
   setLiveObject: (o) => set({ liveObject: o }),
@@ -118,6 +122,7 @@ export const useEditorStore = create<EditorState>((set) => ({
       selectedPlantingId: null,
       focusedObjectId: null,
       armedPlant: null,
+      armedLotId: null,
       armedKind: null,
       liveObject: null,
       livePlanting: null,
diff --git a/web/src/lib/objects.ts b/web/src/lib/objects.ts
index e2e4125..ba391ec 100644
--- a/web/src/lib/objects.ts
+++ b/web/src/lib/objects.ts
@@ -258,6 +258,8 @@ export interface PlantingCreate {
   radiusCm: number
   count?: number | null
   label?: string | null
+  /** Attributes the plop to a purchase, so that lot can report what's left. */
+  seedLotId?: number
 }
 
 export function useCreatePlanting(gardenId: number) {
diff --git a/web/src/lib/plants.ts b/web/src/lib/plants.ts
index 52f885c..65d985a 100644
--- a/web/src/lib/plants.ts
+++ b/web/src/lib/plants.ts
@@ -31,6 +31,10 @@ export const plantSchema = z.object({
   color: z.string(),
   icon: z.string(),
   daysToMaturity: z.number().nullable().optional(),
+  // Provenance for the VARIETY — the page you'd go back to to buy it again.
+  // What you actually bought, and how much is left, lives in seedLots.ts.
+  sourceUrl: z.string().default(''),
+  vendor: z.string().default(''),
   notes: z.string(),
   version: z.number(),
   createdAt: z.string(),
@@ -75,6 +79,8 @@ export interface PlantInput {
   color: string
   icon: string
   daysToMaturity: number | null
+  sourceUrl: string
+  vendor: string
   notes: string
 }
 
diff --git a/web/src/lib/seedLots.test.ts b/web/src/lib/seedLots.test.ts
new file mode 100644
index 0000000..8f35c18
--- /dev/null
+++ b/web/src/lib/seedLots.test.ts
@@ -0,0 +1,149 @@
+import { describe, expect, it } from 'vitest'
+import {
+  attributableLots,
+  formatCost,
+  formatQuantity,
+  formatUnitCost,
+  lotState,
+  lotsByPlant,
+  safeExternalUrl,
+  summarizeLots,
+  type SeedLot,
+} from './seedLots'
+
+function lot(over: Partial<SeedLot> = {}): SeedLot {
+  return {
+    id: 1,
+    ownerId: 1,
+    plantId: 1,
+    vendor: '',
+    sourceUrl: '',
+    sku: '',
+    lotCode: '',
+    quantity: 100,
+    unit: 'seeds',
+    notes: '',
+    version: 1,
+    createdAt: '2026-01-01T00:00:00Z',
+    updatedAt: '2026-01-01T00:00:00Z',
+    used: 0,
+    remaining: 100,
+    ...over,
+  }
+}
+
+describe('safeExternalUrl', () => {
+  // The server already scheme-checks this, but a link is rendered from whatever
+  // the client was handed. "The backend validated it" is not a reason to hand
+  // javascript: to an anchor tag.
+  it('accepts http and https', () => {
+    expect(safeExternalUrl('https://www.johnnyseeds.com/x')).toBe('https://www.johnnyseeds.com/x')
+    expect(safeExternalUrl('http://example.com/')).toBe('http://example.com/')
+  })
+
+  it('refuses everything else', () => {
+    for (const bad of [
+      '',
+      'javascript:alert(1)',
+      'JavaScript:alert(1)',
+      'data:text/html,<script>alert(1)</script>',
+      'file:///etc/passwd',
+      '//evil.example.com',
+      '/seeds/garlic',
+      'not a url',
+    ]) {
+      expect(safeExternalUrl(bad)).toBeNull()
+    }
+  })
+})
+
+describe('lotState', () => {
+  it('reads the state, not just the number', () => {
+    expect(lotState(lot({ quantity: 100, remaining: 100 }))).toBe('ok')
+    expect(lotState(lot({ quantity: 100, remaining: 20 }))).toBe('low')
+    expect(lotState(lot({ quantity: 100, remaining: 0 }))).toBe('empty')
+    // Planting more than you recorded buying is real, and worth showing plainly
+    // rather than clamping to zero.
+    expect(lotState(lot({ quantity: 100, remaining: -5 }))).toBe('over')
+  })
+
+  it('has nothing to say about a lot with no recorded quantity', () => {
+    expect(lotState(lot({ quantity: 0, remaining: 0 }))).toBe('unknown')
+  })
+})
+
+describe('summarizeLots', () => {
+  it('totals remaining and reports the worst state', () => {
+    const s = summarizeLots([
+      lot({ id: 1, quantity: 100, remaining: 80 }),
+      lot({ id: 2, quantity: 50, remaining: 5 }),
+    ])
+    expect(s.remaining).toBe(85)
+    expect(s.unit).toBe('seeds')
+    expect(s.state).toBe('low') // the one that needs attention wins
+  })
+
+  it("drops the unit when lots don't agree, rather than summing dishonestly", () => {
+    const s = summarizeLots([
+      lot({ id: 1, unit: 'seeds', quantity: 100, remaining: 100 }),
+      lot({ id: 2, unit: 'grams', quantity: 10, remaining: 10 }),
+    ])
+    expect(s.unit).toBeNull()
+  })
+
+  it('says nothing for a plant with no lots', () => {
+    expect(summarizeLots([])).toEqual({ remaining: 0, unit: null, state: 'unknown' })
+  })
+})
+
+describe('cost formatting', () => {
+  it('renders whole currency from cents', () => {
+    expect(formatCost(499)).toBe('$4.99')
+    expect(formatCost(undefined)).toBeNull()
+  })
+
+  it('gives per-unit cost extra precision when it would round to nothing', () => {
+    expect(formatUnitCost(lot({ costCents: 499, quantity: 100 }))).toBe('$0.050/seed')
+    expect(formatUnitCost(lot({ costCents: 1200, quantity: 4, unit: 'packets' }))).toBe('$3.00/packet')
+  })
+
+  it('has no per-unit cost without both halves', () => {
+    expect(formatUnitCost(lot({ costCents: undefined }))).toBeNull()
+    expect(formatUnitCost(lot({ costCents: 499, quantity: 0 }))).toBeNull()
+  })
+})
+
+describe('lotsByPlant', () => {
+  it('groups, and copes with nothing', () => {
+    const grouped = lotsByPlant([lot({ id: 1, plantId: 7 }), lot({ id: 2, plantId: 7 }), lot({ id: 3, plantId: 9 })])
+    expect(grouped.get(7)?.length).toBe(2)
+    expect(grouped.get(9)?.length).toBe(1)
+    expect(lotsByPlant(undefined).size).toBe(0)
+  })
+})
+
+describe('attributableLots', () => {
+  // An exhausted lot is still offered: the count records what was written down,
+  // not a fact about the packet, so refusing to attribute a planting because the
+  // number says zero would make a wrong number harder to correct, not easier.
+  it('offers exhausted lots, just not first', () => {
+    const empty = lot({ id: 1, remaining: 0 })
+    const full = lot({ id: 2, remaining: 100 })
+    expect(attributableLots([empty, full]).map((l) => l.id)).toEqual([2, 1])
+    expect(attributableLots([empty]).length).toBe(1)
+  })
+
+  it("doesn't mutate its input", () => {
+    const lots = [lot({ id: 1, remaining: 0 }), lot({ id: 2, remaining: 100 })]
+    attributableLots(lots)
+    expect(lots.map((l) => l.id)).toEqual([1, 2])
+  })
+})
+
+describe('formatQuantity', () => {
+  it('keeps whole counts whole and fractional ones readable', () => {
+    expect(formatQuantity(100)).toBe('100')
+    expect(formatQuantity(12.5)).toBe('12.5')
+    expect(formatQuantity(-15)).toBe('-15') // over-planted lots go negative
+  })
+})
diff --git a/web/src/lib/seedLots.ts b/web/src/lib/seedLots.ts
new file mode 100644
index 0000000..0d9c4f1
--- /dev/null
+++ b/web/src/lib/seedLots.ts
@@ -0,0 +1,212 @@
+// Seed lots (#51): what you actually bought, and what's left of it.
+//
+// A lot is one purchase of one variety. Inventory belongs to the purchase rather
+// than to the variety because the same garlic from two vendors in two years is
+// two different things — see #50 for the reasoning behind the shape.
+
+import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
+import { z } from 'zod'
+import { ApiError, api } from './api'
+
+export const lotUnitSchema = z.enum(['seeds', 'grams', 'ounces', 'packets', 'bulbs', 'plants'])
+export type LotUnit = z.infer<typeof lotUnitSchema>
+
+export const LOT_UNITS: { value: LotUnit; label: string }[] = [
+  { value: 'seeds', label: 'seeds' },
+  { value: 'grams', label: 'grams' },
+  { value: 'ounces', label: 'ounces' },
+  { value: 'packets', label: 'packets' },
+  { value: 'bulbs', label: 'bulbs' },
+  { value: 'plants', label: 'plants' },
+]
+
+export const seedLotSchema = z.object({
+  id: z.number(),
+  ownerId: z.number(),
+  plantId: z.number(),
+  vendor: z.string(),
+  sourceUrl: z.string(),
+  sku: z.string(),
+  lotCode: z.string(),
+  purchasedAt: z.string().optional(),
+  packedForYear: z.number().optional(),
+  quantity: z.number(),
+  unit: lotUnitSchema,
+  costCents: z.number().optional(),
+  germinationPct: z.number().optional(),
+  notes: z.string(),
+  version: z.number(),
+  createdAt: z.string(),
+  updatedAt: z.string(),
+  // Computed server-side: used is the summed effective count of active
+  // plantings attributed to this lot; remaining is quantity - used, and may be
+  // NEGATIVE when more was planted than the lot recorded buying.
+  used: z.number(),
+  remaining: z.number(),
+})
+export type SeedLot = z.infer<typeof seedLotSchema>
+
+const seedLotsKey = ['seed-lots'] as const
+
+export function useSeedLots() {
+  return useQuery({
+    queryKey: seedLotsKey,
+    queryFn: async (): Promise<SeedLot[]> => z.array(seedLotSchema).parse(await api.get('/seed-lots')),
+  })
+}
+
+export interface SeedLotInput {
+  plantId: number
+  vendor: string
+  sourceUrl: string
+  sku: string
+  lotCode: string
+  purchasedAt: string | null
+  packedForYear: number | null
+  quantity: number
+  unit: LotUnit
+  costCents: number | null
+  germinationPct: number | null
+  notes: string
+}
+
+function invalidate(qc: ReturnType<typeof useQueryClient>) {
+  void qc.invalidateQueries({ queryKey: seedLotsKey })
+}
+
+export function useCreateSeedLot() {
+  const qc = useQueryClient()
+  return useMutation({
+    mutationFn: async (input: SeedLotInput): Promise<SeedLot> =>
+      seedLotSchema.parse(await api.post('/seed-lots', input)),
+    onSuccess: () => invalidate(qc),
+  })
+}
+
+export function useUpdateSeedLot() {
+  const qc = useQueryClient()
+  return useMutation({
+    mutationFn: async (vars: Partial<SeedLotInput> & { id: number; version: number }): Promise<SeedLot> => {
+      const { id, ...rest } = vars
+      return seedLotSchema.parse(await api.patch(`/seed-lots/${id}`, rest))
+    },
+    onSuccess: () => invalidate(qc),
+  })
+}
+
+export function useDeleteSeedLot() {
+  const qc = useQueryClient()
+  return useMutation({
+    mutationFn: async (id: number): Promise<void> => {
+      await api.delete(`/seed-lots/${id}`)
+    },
+    onSuccess: () => invalidate(qc),
+  })
+}
+
+/**
+ * The lots a placement could be attributed to, best first.
+ *
+ * Lots with seed left come first, but an exhausted one is still offered: the
+ * count is a record of what you wrote down, not a fact about the packet, and
+ * refusing to attribute a planting because the number says zero would make the
+ * number harder to correct rather than easier.
+ */
+export function attributableLots(lots: SeedLot[]): SeedLot[] {
+  return [...lots].sort((a, b) => Number(b.remaining > 0) - Number(a.remaining > 0))
+}
+
+/** The current server row carried by a 409, so an edit form can rebase onto it
+ *  and the user can re-save rather than losing what they typed. Every other
+ *  entity's form does this; a lot is no different. */
+export function conflictSeedLot(err: unknown): SeedLot | null {
+  if (!(err instanceof ApiError) || !err.isConflict) return null
+  const parsed = seedLotSchema.safeParse((err.body as { current?: unknown })?.current)
+  return parsed.success ? parsed.data : null
+}
+
+/** Group lots by the plant they belong to. */
+export function lotsByPlant(lots: SeedLot[] | undefined): Map<number, SeedLot[]> {
+  const map = new Map<number, SeedLot[]>()
+  for (const lot of lots ?? []) {
+    const list = map.get(lot.plantId)
+    if (list) list.push(lot)
+    else map.set(lot.plantId, [lot])
+  }
+  return map
+}
+
+/**
+ * How a lot is doing, as a state rather than a number — this is the thing you
+ * scan for when deciding what to order, and a number alone doesn't survive being
+ * skimmed down a list.
+ *
+ * "over" means more was planted than the lot recorded buying. That's a real
+ * situation (a miscounted packet, a lot entered after the fact) and worth
+ * showing plainly rather than clamping to zero and hiding the discrepancy.
+ */
+export type LotState = 'over' | 'empty' | 'low' | 'ok' | 'unknown'
+
+const LOW_FRACTION = 0.2
+
+export function lotState(lot: SeedLot): LotState {
+  if (lot.quantity <= 0) return 'unknown' // no quantity recorded: nothing to be low on
+  if (lot.remaining < 0) return 'over'
+  if (lot.remaining === 0) return 'empty'
+  if (lot.remaining / lot.quantity <= LOW_FRACTION) return 'low'
+  return 'ok'
+}
+
+/** The total remaining across a plant's lots, and the worst state among them —
+ *  what a plant card shows before you open it. */
+export function summarizeLots(lots: SeedLot[]): { remaining: number; unit: LotUnit | null; state: LotState } {
+  if (lots.length === 0) return { remaining: 0, unit: null, state: 'unknown' }
+  // Mixed units can't be summed honestly; report the majority unit's total only
+  // when they all agree, else leave the unit off and let the per-lot rows speak.
+  const unit = lots.every((l) => l.unit === lots[0].unit) ? lots[0].unit : null
+  const remaining = lots.reduce((sum, l) => sum + l.remaining, 0)
+  const order: LotState[] = ['over', 'empty', 'low', 'ok', 'unknown']
+  const state = order.find((s) => lots.some((l) => lotState(l) === s)) ?? 'unknown'
+  return { remaining, unit, state }
+}
+
+/** Quantities are stored as REAL because grams and ounces are fractional, but a
+ *  whole number of seeds shouldn't render as "100.0". */
+export function formatQuantity(n: number): string {
+  return Number.isInteger(n) ? String(n) : n.toFixed(1)
+}
+
+/** Whole currency from cents, e.g. 499 → "$4.99". */
+export function formatCost(cents: number | undefined): string | null {
+  if (cents == null) return null
+  return new Intl.NumberFormat(undefined, { style: 'currency', currency: 'USD' }).format(cents / 100)
+}
+
+/** Cost per unit, when both are known and it says something useful. */
+export function formatUnitCost(lot: SeedLot): string | null {
+  if (lot.costCents == null || lot.quantity <= 0) return null
+  const per = lot.costCents / 100 / lot.quantity
+  return `${new Intl.NumberFormat(undefined, { style: 'currency', currency: 'USD', minimumFractionDigits: per < 0.1 ? 3 : 2 }).format(per)}/${singular(lot.unit)}`
+}
+
+function singular(unit: LotUnit): string {
+  return unit.endsWith('s') ? unit.slice(0, -1) : unit
+}
+
+/**
+ * Whether a stored URL is safe to render as a link.
+ *
+ * The server already scheme-checks this (#50), but a link is rendered from
+ * whatever the client was handed — an old row, a different server version, a
+ * response someone tampered with — and "the backend validated it" is not a
+ * reason to hand `javascript:` to an anchor tag. Cheap to check twice.
+ */
+export function safeExternalUrl(raw: string): string | null {
+  if (!raw) return null
+  try {
+    const u = new URL(raw)
+    return u.protocol === 'http:' || u.protocol === 'https:' ? u.toString() : null
+  } catch {
+    return null
+  }
+}
diff --git a/web/src/pages/GardenEditorPage.tsx b/web/src/pages/GardenEditorPage.tsx
index c1655e8..8a43ab6 100644
--- a/web/src/pages/GardenEditorPage.tsx
+++ b/web/src/pages/GardenEditorPage.tsx
@@ -31,6 +31,7 @@ import {
 import { toEditorPlanting } from '@/lib/plantings'
 import type { Plant } from '@/lib/plants'
 import { useJournalCounts } from '@/lib/journal'
+import { attributableLots, lotsByPlant, useSeedLots, type SeedLot } from '@/lib/seedLots'
 import { useSeedTray } from '@/lib/seedTray'
 import { usePageTitle } from '@/lib/usePageTitle'
 
@@ -74,6 +75,8 @@ export function GardenEditorPage() {
   const updateObject = useUpdateObject(gid)
   const ensurePlant = useEnsurePlantInFull(gid)
   const { trayPlants, add: addToTray, remove: removeFromTray } = useSeedTray(gid)
+  const seedLots = useSeedLots()
+  const lotsByPlantId = useMemo(() => lotsByPlant(seedLots.data), [seedLots.data])
 
   // Which plant-picker flow is open: 'place' arms a plant for repeat placement;
   // 'change' swaps the selected plop's plant.
@@ -277,9 +280,18 @@ export function GardenEditorPage() {
   // Arm a plant for tap-to-place. The full catalog carries plants not yet in this
   // garden's /full payload, so make sure the chosen one is in the cache first —
   // otherwise its placed plops render without an icon/color until a refetch.
-  function armPlant(plant: Plant) {
+  // The Seed Tray arms a plant directly, without going through the picker, so it
+  // has to do the picker's single-lot auto-attribution itself — otherwise the
+  // quickest way to place a plant is the one path that silently loses which
+  // packet it came from. Several lots is genuinely ambiguous, so that case stays
+  // unattributed rather than guessing; the picker is where you choose.
+  function armPlant(plant: Plant, lot?: SeedLot) {
     ensurePlant(plant)
-    setArmedPlant(plant)
+    if (lot === undefined) {
+      const lots = attributableLots(lotsByPlantId.get(plant.id) ?? [])
+      lot = lots.length === 1 ? lots[0] : undefined
+    }
+    setArmedPlant(plant, lot?.id ?? null)
   }
 
   // Removing the armed plant from the tray also disarms it, so placement doesn't
@@ -294,14 +306,14 @@ export function GardenEditorPage() {
   // a not-yet-placed plant isn't in that map, which used to silently abort the
   // pick (nothing armed, picker left open). Picking (place OR change) makes sure
   // the plant renders and drops it into this garden's tray for quick reuse.
-  function onPickPlant(plant: Plant) {
+  function onPickPlant(plant: Plant, lot?: SeedLot) {
     if (!canEdit) return // defense in depth: viewers can't reach the picker anyway
     ensurePlant(plant)
     addToTray(plant)
     if (picker === 'change' && selectedPlop) {
       updatePlanting.mutate({ id: selectedPlop.id, version: selectedPlop.version, plantId: plant.id })
     } else {
-      setArmedPlant(plant) // 'place' mode: arm for repeat placement
+      setArmedPlant(plant, lot?.id ?? null) // 'place' mode: arm for repeat placement
     }
     setPicker(null)
   }
diff --git a/web/src/pages/PlantsPage.tsx b/web/src/pages/PlantsPage.tsx
index 37c91f7..fbc167e 100644
--- a/web/src/pages/PlantsPage.tsx
+++ b/web/src/pages/PlantsPage.tsx
@@ -7,8 +7,11 @@ import { CategoryChips } from '@/components/plants/CategoryChips'
 import { PlantCard } from '@/components/plants/PlantCard'
 import { PlantFormModal } from '@/components/plants/PlantFormModal'
 import { DeletePlantModal } from '@/components/plants/DeletePlantModal'
+import { SeedLotModal } from '@/components/plants/SeedLotModal'
+import { DeleteSeedLotModal } from '@/components/plants/DeleteSeedLotModal'
 import { PlantPicker } from '@/editor/PlantPicker'
 import { filterPlants, usePlants, type CategoryFilter, type Plant } from '@/lib/plants'
+import { lotsByPlant, useSeedLots, type SeedLot } from '@/lib/seedLots'
 import type { UnitPref } from '@/lib/units'
 import { usePageTitle } from '@/lib/usePageTitle'
 
@@ -19,6 +22,9 @@ type Dialog =
   | { kind: 'duplicate'; plant: Plant }
   | { kind: 'delete'; plant: Plant }
   | { kind: 'picker' }
+  | { kind: 'addLot'; plant: Plant }
+  | { kind: 'editLot'; plant: Plant; lot: SeedLot }
+  | { kind: 'deleteLot'; lot: SeedLot }
   | null
 
 // There's no per-user unit preference server-side (only per-garden), so the
@@ -35,6 +41,8 @@ function loadUnit(): UnitPref {
 export function PlantsPage() {
   usePageTitle('Plants')
   const plants = usePlants()
+  const seedLots = useSeedLots()
+  const lots = useMemo(() => lotsByPlant(seedLots.data), [seedLots.data])
   const [unit, setUnit] = useState<UnitPref>(() => loadUnit())
   const [query, setQuery] = useState('')
   const [category, setCategory] = useState<CategoryFilter>('all')
@@ -108,9 +116,13 @@ export function PlantsPage() {
                 key={p.id}
                 plant={p}
                 unit={unit}
+                lots={lots.get(p.id) ?? []}
                 onEdit={() => setDialog({ kind: 'edit', plant: p })}
                 onDelete={() => setDialog({ kind: 'delete', plant: p })}
                 onDuplicate={() => setDialog({ kind: 'duplicate', plant: p })}
+                onAddLot={() => setDialog({ kind: 'addLot', plant: p })}
+                onEditLot={(lot) => setDialog({ kind: 'editLot', plant: p, lot })}
+                onDeleteLot={(lot) => setDialog({ kind: 'deleteLot', lot })}
               />
             ))}
           </div>
@@ -121,6 +133,9 @@ export function PlantsPage() {
       {dialog?.kind === 'edit' && <PlantFormModal plant={dialog.plant} unit={unit} onClose={close} />}
       {dialog?.kind === 'duplicate' && <PlantFormModal template={dialog.plant} unit={unit} onClose={close} />}
       {dialog?.kind === 'delete' && <DeletePlantModal plant={dialog.plant} onClose={close} />}
+      {dialog?.kind === 'addLot' && <SeedLotModal plant={dialog.plant} onClose={close} />}
+      {dialog?.kind === 'editLot' && <SeedLotModal plant={dialog.plant} lot={dialog.lot} onClose={close} />}
+      {dialog?.kind === 'deleteLot' && <DeleteSeedLotModal lot={dialog.lot} onClose={close} />}
       {dialog?.kind === 'picker' && (
         <PlantPicker
           unit={unit}