web/src/components/plants/CategoryChips.tsx

@@ -0,0 +1,37 @@
+import { cn } from '@/lib/cn'
+import { CATEGORY_LABELS, PLANT_CATEGORIES, type CategoryFilter } from '@/lib/plants'
+
+/**
+ * Horizontal, scrollable "All + each category" chip row. Shared by the /plants
+ * page and the PlantPicker so both filter the catalog identically.
+ */
+export function CategoryChips({
+  value,
+  onChange,
+  size = 'md',
+}: {
+  value: CategoryFilter
+  onChange: (c: CategoryFilter) => void
+  size?: 'sm' | 'md'
+}) {
+  const chip = (v: CategoryFilter, label: string) => (
+    <button
+      key={v}
+      type="button"
+      onClick={() => onChange(v)}
+      className={cn(
+        'shrink-0 rounded-full px-3 font-medium transition-colors',
+        size === 'sm' ? 'py-1 text-xs' : 'py-1 text-sm',
+        value === v ? 'bg-accent text-accent-contrast' : 'bg-border/50 text-muted hover:text-fg',
+      )}
+    >
+      {label}
+    </button>
+  )
+  return (
+    <div className="flex gap-1.5 overflow-x-auto">
+      {chip('all', 'All')}
+      {PLANT_CATEGORIES.map((c) => chip(c, CATEGORY_LABELS[c]))}
+    </div>
+  )
+}

web/src/components/plants/DeletePlantModal.tsx

@@ -0,0 +1,46 @@
+import { useState } from 'react'
+import { Modal } from '@/components/ui/Modal'
+import { Alert } from '@/components/ui/Alert'
+import { Button } from '@/components/ui/Button'
+import { errorMessage } from '@/lib/api'
+import { useDeletePlant, type Plant } from '@/lib/plants'
+
+/**
+ * Confirmation dialog for deleting a custom plant. A plant still used by
+ * plantings is refused by the server (409 PLANT_IN_USE); we surface that
+ * message inline rather than pretending it worked.
+ */
+export function DeletePlantModal({ plant, onClose }: { plant: Plant; onClose: () => void }) {
+  const deletion = useDeletePlant()
+  const [error, setError] = useState<string | null>(null)
+
+  async function onConfirm() {
+    setError(null)
+    try {
+      await deletion.mutateAsync(plant.id)
+      onClose()
+    } catch (err) {
+      setError(errorMessage(err, 'Could not delete the plant.'))
+    }
+  }
+
+  return (
+    <Modal title="Delete plant" onClose={onClose} busy={deletion.isPending}>
+      <div className="flex flex-col gap-4">
+        <p className="text-sm text-muted">
+          Delete <span className="font-medium text-fg">{plant.name}</span> from your catalog? This can't be
+          undone.
+        </p>
+        {error && <Alert>{error}</Alert>}
+        <div className="flex justify-end gap-2">
+          <Button type="button" variant="ghost" onClick={onClose} disabled={deletion.isPending}>
+            Cancel
+          </Button>
+          <Button type="button" variant="danger" onClick={onConfirm} disabled={deletion.isPending}>
+            {deletion.isPending ? 'Deleting…' : 'Delete'}
+          </Button>
+        </div>
+      </div>
+    </Modal>
+  )
+}

web/src/components/plants/PlantCard.tsx

@@ -0,0 +1,72 @@
+import { PlantIcon } from './PlantIcon'
+import { CATEGORY_LABELS, isBuiltin, type Plant } from '@/lib/plants'
+import { formatSpacing, type UnitPref } from '@/lib/units'
+
+const actionClass =
+  'rounded-md px-2.5 py-1 text-sm font-medium text-muted outline-none transition-colors ' +
+  'hover:bg-border/50 hover:text-fg focus-visible:ring-2 focus-visible:ring-accent/40'
+const dangerClass =
+  'rounded-md px-2.5 py-1 text-sm font-medium text-muted outline-none transition-colors ' +
+  'hover:bg-red-500/10 hover:text-red-600 focus-visible:ring-2 focus-visible:ring-red-500/40 dark:hover:text-red-400'
+
+/**
+ * One catalog plant as a card: icon tile tinted with the plant's color, name,
+ * category + mature spacing (unit-aware), and actions. Built-ins are badged and
+ * offer only "Duplicate" (they're read-only); own plants add Edit/Delete.
+ */
+export function PlantCard({
+  plant,
+  unit,
+  onEdit,
+  onDelete,
+  onDuplicate,
+}: {
+  plant: Plant
+  unit: UnitPref
+  onEdit: () => void
+  onDelete: () => void
+  onDuplicate: () => void
+}) {
+  const builtin = isBuiltin(plant)
+  return (
+    <div className="flex flex-col rounded-xl border border-border bg-surface">
+      <div className="flex items-start gap-3 p-4">
+        <PlantIcon color={plant.color} icon={plant.icon} className="h-11 w-11 rounded-lg text-2xl" />
+        <div className="min-w-0 flex-1">
+          <div className="flex items-center gap-2">
+            <h3 className="truncate font-semibold text-fg">{plant.name}</h3>
+            {builtin && (
+              <span className="shrink-0 rounded bg-border/60 px-1.5 py-0.5 text-[10px] font-medium uppercase tracking-wide text-muted">
+                Built-in
+              </span>
+            )}
+          </div>
+          <p className="mt-0.5 text-sm text-muted">
+            {CATEGORY_LABELS[plant.category]} · {formatSpacing(plant.spacingCm, unit)} spacing
+          </p>
+          {plant.notes && <p className="mt-1 line-clamp-2 text-xs text-muted">{plant.notes}</p>}
+        </div>
+        <span
+          className="mt-1 h-4 w-4 shrink-0 rounded-full border border-black/10 dark:border-white/10"
+          style={{ backgroundColor: plant.color }}
+          title={plant.color}
+        />
+      </div>
+      <div className="flex justify-end gap-1 border-t border-border px-2 py-1.5">
+        <button type="button" onClick={onDuplicate} className={actionClass}>
+          Duplicate
+        </button>
+        {!builtin && (
+          <button type="button" onClick={onEdit} className={actionClass}>
+            Edit
+          </button>
+        )}
+        {!builtin && (
+          <button type="button" onClick={onDelete} className={dangerClass}>
+            Delete
+          </button>
+        )}
+      </div>
+    </div>
+  )
+}

web/src/components/plants/PlantFormModal.tsx

@@ -0,0 +1,212 @@
+import { useState, type FormEvent } from 'react'
+import { Modal } from '@/components/ui/Modal'
+import { Alert } from '@/components/ui/Alert'
+import { Button } from '@/components/ui/Button'
+import { Select } from '@/components/ui/Select'
+import { TextArea } from '@/components/ui/TextArea'
+import { TextField } from '@/components/ui/TextField'
+import { errorMessage } from '@/lib/api'
+import {
+  CATEGORY_LABELS,
+  PLANT_CATEGORIES,
+  conflictPlant,
+  useCreatePlant,
+  useUpdatePlant,
+  type Plant,
+  type PlantCategory,
+  type PlantInput,
+} from '@/lib/plants'
+import { cmFromSpacing, spacingFromCm, spacingUnitLabel, type UnitPref } from '@/lib/units'
+
+const DEFAULT_COLOR = '#4a7c3f'
+const DEFAULT_ICON = '🌱'
+
+const categoryOptions = PLANT_CATEGORIES.map((c) => ({ value: c, label: CATEGORY_LABELS[c] }))
+
+/** Expand a #rgb shorthand to #rrggbb so the native color input renders it. */
+function expandHex(color: string): string {
+  if (/^#[0-9a-fA-F]{3}$/.test(color)) {
+    const [, r, g, b] = color
+    return `#${r}${r}${g}${g}${b}${b}`
+  }
+  return /^#[0-9a-fA-F]{6}$/.test(color) ? color : DEFAULT_COLOR
+}
+
+/**
+ * Create or edit a custom plant. `plant` puts it in edit mode; `template` (a
+ * built-in or another plant, used by "Duplicate") pre-fills a fresh create. A
+ * 409 rebases the form onto the server's current row. Spacing is entered in the
+ * page's unit and converted to centimeters for the API.
+ */
+export function PlantFormModal({
+  plant,
+  template,
+  unit,
+  onClose,
+}: {
+  plant?: Plant
+  template?: Plant
+  unit: UnitPref
+  onClose: () => void
+}) {
+  const isEdit = !!plant
+  const source = plant ?? template
+  const create = useCreatePlant()
+  const update = useUpdatePlant()
+  const pending = create.isPending || update.isPending
+
+  const [name, setName] = useState(source ? (isEdit ? source.name : `${source.name} (copy)`) : '')
+  const [category, setCategory] = useState<PlantCategory>(source?.category ?? 'vegetable')
+  const [spacing, setSpacing] = useState(String(spacingFromCm(source?.spacingCm ?? 30, unit)))
+  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 [notes, setNotes] = useState(source?.notes ?? '')
+  const [version, setVersion] = useState(plant?.version ?? 0)
+  const [conflict, setConflict] = useState<string | null>(null)
+  const [formError, setFormError] = useState<string | null>(null)
+  const unitLabel = spacingUnitLabel(unit)
+
+  async function onSubmit(e: FormEvent) {
+    e.preventDefault()
+    setFormError(null)
+    setConflict(null)
+
+    if (!name.trim()) {
+      setFormError('Enter a name for the plant.')
+      return
+    }
+    if (!icon.trim()) {
+      setFormError('Pick an emoji icon.')
+      return
+    }
+    const spacingCm = cmFromSpacing(parseFloat(spacing), unit)
+    if (!Number.isFinite(spacingCm) || spacingCm < 1) {
+      setFormError(`Spacing must be at least 1 ${unitLabel}.`)
+      return
+    }
+    let daysToMaturity: number | null = null
+    if (days.trim()) {
+      // Number() (not parseInt) so "1.5" is rejected, not silently truncated to 1.
+      const d = Number(days)
+      if (!Number.isInteger(d) || d < 1) {
+        setFormError('Days to maturity must be a whole number of days, or left blank.')
+        return
+      }
+      daysToMaturity = d
+    }
+
+    const input: PlantInput = {
+      name: name.trim(),
+      category,
+      spacingCm,
+      color,
+      icon: icon.trim(),
+      daysToMaturity,
+      notes: notes.trim(),
+    }
+
+    try {
+      if (isEdit) {
+        await update.mutateAsync({ id: plant.id, ...input, version })
+      } else {
+        await create.mutateAsync(input)
+      }
+      onClose()
+    } catch (err) {
+      const current = conflictPlant(err)
+      if (current) {
+        // Someone else changed this plant: rebase onto the fresh row so a re-save
+        // applies against the current version.
+        setVersion(current.version)
+        setName(current.name)
+        setCategory(current.category)
+        setSpacing(String(spacingFromCm(current.spacingCm, unit)))
+        setColor(expandHex(current.color))
+        setIcon(current.icon)
+        setDays(current.daysToMaturity != null ? String(current.daysToMaturity) : '')
+        setNotes(current.notes)
+        setConflict('This plant changed elsewhere. The latest values are shown — review and save again.')
+        return
+      }
+      setFormError(errorMessage(err, isEdit ? 'Could not save changes.' : 'Could not create the plant.'))
+    }
+  }
+
+  return (
+    <Modal title={isEdit ? 'Edit plant' : 'New plant'} onClose={onClose} busy={pending}>
+      <form onSubmit={onSubmit} className="flex flex-col gap-3">
+        {conflict && <Alert tone="info">{conflict}</Alert>}
+
+        <TextField label="Name" name="name" required value={name} onChange={(e) => setName(e.target.value)} />
+
+        <div className="grid grid-cols-2 gap-3">
+          <Select
+            label="Category"
+            name="category"
+            value={category}
+            onChange={(e) => setCategory(e.target.value as PlantCategory)}
+            options={categoryOptions}
+          />
+          <TextField
+            label={`Spacing (${unitLabel})`}
+            name="spacing"
+            type="number"
+            inputMode="decimal"
+            step="any"
+            min="1"
+            required
+            value={spacing}
+            onChange={(e) => setSpacing(e.target.value)}
+          />
+        </div>
+
+        <div className="grid grid-cols-2 gap-3">
+          <div className="flex flex-col gap-1.5">
+            <label htmlFor="plant-color" className="text-sm font-medium text-fg">
+              Color
+            </label>
+            <input
+              id="plant-color"
+              type="color"
+              value={color}
+              onChange={(e) => setColor(e.target.value)}
+              className="h-10 w-full cursor-pointer rounded-md border border-border bg-surface"
+            />
+          </div>
+          <TextField
+            label="Icon (emoji)"
+            name="icon"
+            value={icon}
+            onChange={(e) => setIcon(e.target.value)}
+            hint="A single emoji, e.g. 🍅"
+          />
+        </div>
+
+        <TextField
+          label="Days to maturity (optional)"
+          name="days"
+          type="number"
+          inputMode="numeric"
+          step="1"
+          min="1"
+          value={days}
+          onChange={(e) => setDays(e.target.value)}
+        />
+
+        <TextArea label="Notes" name="notes" rows={2} value={notes} onChange={(e) => setNotes(e.target.value)} />
+
+        {formError && <Alert>{formError}</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' : 'Create plant'}
+          </Button>
+        </div>
+      </form>
+    </Modal>
+  )
+}

web/src/components/plants/PlantIcon.tsx

@@ -0,0 +1,18 @@
+import { cn } from '@/lib/cn'
+
+/**
+ * A plant's emoji on a tile tinted with its own color (via color-mix, so any
+ * valid CSS color works). Shared by PlantCard and the PlantPicker rows. Size and
+ * shape come from `className`.
+ */
+export function PlantIcon({ color, icon, className }: { color: string; icon: string; className?: string }) {
+  return (
+    <span
+      className={cn('grid shrink-0 place-items-center', className)}
+      style={{ backgroundColor: `color-mix(in srgb, ${color} 18%, transparent)` }}
+      aria-hidden
+    >
+      {icon}
+    </span>
+  )
+}

web/src/editor/PlantPicker.tsx

@@ -0,0 +1,156 @@
+import { useEffect, useMemo, useRef, useState } from 'react'
+import { cn } from '@/lib/cn'
+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 { formatSpacing, type UnitPref } from '@/lib/units'
+
+const RECENT_KEY = 'pansy:recent-plants'
+const RECENT_MAX = 8
+
+/** Recently-picked plant ids, most-recent first, from localStorage. */
+function loadRecent(): number[] {
+  try {
+    const v: unknown = JSON.parse(localStorage.getItem(RECENT_KEY) ?? '[]')
+    return Array.isArray(v) ? v.filter((n): n is number => typeof n === 'number') : []
+  } catch {
+    return []
+  }
+}
+
+/** Prepend id (dedup, capped) and persist; returns the new list. */
+function recordRecent(id: number): number[] {
+  const next = [id, ...loadRecent().filter((n) => n !== id)].slice(0, RECENT_MAX)
+  try {
+    localStorage.setItem(RECENT_KEY, JSON.stringify(next))
+  } catch {
+    // Recents are a nicety; ignore quota/availability failures.
+  }
+  return next
+}
+
+/**
+ * Reusable plant chooser: a search-first list with a recently-used shortcut and
+ * category filter, rendered as a bottom sheet on mobile / centered panel on
+ * desktop. `onSelect` fires with the chosen plant (and records it as recent).
+ * The plops editor (#15) opens this when placing plants; /plants demos it.
+ */
+export function PlantPicker({
+  onSelect,
+  onClose,
+  unit = 'metric',
+}: {
+  onSelect: (plant: Plant) => void
+  onClose: () => void
+  unit?: UnitPref
+}) {
+  const plants = usePlants()
+  const [query, setQuery] = useState('')
+  const [category, setCategory] = useState<CategoryFilter>('all')
+  const [recent, setRecent] = useState<number[]>(() => loadRecent())
+  const searchRef = useRef<HTMLInputElement>(null)
+  const onCloseRef = useRef(onClose)
+  onCloseRef.current = onClose
+
+  useEffect(() => {
+    searchRef.current?.focus()
+    function onKey(e: KeyboardEvent) {
+      if (e.key === 'Escape') onCloseRef.current()
+    }
+    document.addEventListener('keydown', onKey)
+    return () => document.removeEventListener('keydown', onKey)
+  }, [])
+
+  const all = useMemo(() => plants.data ?? [], [plants.data])
+
+  const filtered = useMemo(() => filterPlants(all, query, category), [all, query, category])
+
+  // Recents show only when not actively searching, and only rows still present.
+  const recentPlants = useMemo(() => {
+    if (query.trim() !== '') return []
+    const byId = new Map(all.map((p) => [p.id, p]))
+    return recent.map((id) => byId.get(id)).filter((p): p is Plant => !!p)
+  }, [all, recent, query])
+
+  function choose(p: Plant) {
+    setRecent(recordRecent(p.id))
+    onSelect(p)
+  }
+
+  // A plant option row. keyPrefix namespaces the key so a plant appearing in
+  // both the Recent and All sections doesn't collide on a duplicate React key.
+  const row = (p: Plant, keyPrefix: string) => (
+    <button
+      key={`${keyPrefix}-${p.id}`}
+      type="button"
+      onClick={() => choose(p)}
+      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"
+    >
+      <PlantIcon color={p.color} icon={p.icon} className="h-9 w-9 rounded-md text-xl" />
+      <span className="min-w-0 flex-1">
+        <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)}
+        </span>
+      </span>
+    </button>
+  )
+
+  return (
+    <div
+      className="fixed inset-0 z-50 flex items-end justify-center bg-black/40 sm:items-center sm:p-4"
+      onMouseDown={(e) => e.target === e.currentTarget && onClose()}
+    >
+      <div
+        role="dialog"
+        aria-modal="true"
+        aria-label="Choose a plant"
+        className="flex max-h-[85vh] w-full flex-col rounded-t-2xl border border-border bg-surface shadow-xl sm:max-w-lg sm:rounded-2xl"
+      >
+        <div className="flex items-center gap-2 border-b border-border p-3">
+          <input
+            ref={searchRef}
+            type="search"
+            value={query}
+            onChange={(e) => setQuery(e.target.value)}
+            placeholder="Search plants…"
+            aria-label="Search plants"
+            className={cn(fieldControlClass, 'min-w-0 flex-1')}
+          />
+          <button
+            type="button"
+            onClick={onClose}
+            aria-label="Close"
+            className="rounded-md px-2 py-2 text-muted outline-none transition-colors hover:bg-border/50 hover:text-fg focus-visible:ring-2 focus-visible:ring-accent/40"
+          >
+            ✕
+          </button>
+        </div>
+
+        <div className="border-b border-border px-3 py-2">
+          <CategoryChips value={category} onChange={setCategory} size="sm" />
+        </div>
+
+        <div className="min-h-0 flex-1 overflow-y-auto p-2">
+          {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>}
+
+          {recentPlants.length > 0 && (
+            <>
+              <p className="px-3 pb-1 pt-2 text-xs font-semibold uppercase tracking-wide text-muted">Recent</p>
+              {recentPlants.map((p) => row(p, 'recent'))}
+              <p className="px-3 pb-1 pt-3 text-xs font-semibold uppercase tracking-wide text-muted">All plants</p>
+            </>
+          )}
+
+          {filtered.map((p) => row(p, 'all'))}
+
+          {plants.isSuccess && filtered.length === 0 && (
+            <p className="p-4 text-sm text-muted">No plants match your search.</p>
+          )}
+        </div>
+      </div>
+    </div>
+  )
+}

web/src/lib/plants.ts

@@ -0,0 +1,122 @@
+// Plant catalog data layer: zod-validated shapes for /api/v1/plants plus the
+// react-query hooks the /plants page and PlantPicker use. Built-ins (ownerId
+// null) are seeded and read-only; a user's own rows are editable. "Cloning" a
+// built-in is just a create of a copy (no special endpoint).
+
+import { queryOptions, useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
+import { z } from 'zod'
+import { ApiError, api } from './api'
+
+export const PLANT_CATEGORIES = ['vegetable', 'herb', 'flower', 'fruit', 'tree_shrub', 'cover'] as const
+export type PlantCategory = (typeof PLANT_CATEGORIES)[number]
+
+export const CATEGORY_LABELS: Record<PlantCategory, string> = {
+  vegetable: 'Vegetable',
+  herb: 'Herb',
+  flower: 'Flower',
+  fruit: 'Fruit',
+  tree_shrub: 'Tree / shrub',
+  cover: 'Cover crop',
+}
+
+const plantCategorySchema = z.enum(PLANT_CATEGORIES)
+
+export const plantSchema = z.object({
+  id: z.number(),
+  // Absent (built-in) or a user id. The API omits ownerId for built-ins.
+  ownerId: z.number().nullable().optional(),
+  name: z.string(),
+  category: plantCategorySchema,
+  spacingCm: z.number(),
+  color: z.string(),
+  icon: z.string(),
+  daysToMaturity: z.number().nullable().optional(),
+  notes: z.string(),
+  version: z.number(),
+  createdAt: z.string(),
+  updatedAt: z.string(),
+})
+export type Plant = z.infer<typeof plantSchema>
+
+/** A built-in (seeded, read-only) plant has no owner. */
+export function isBuiltin(p: Plant): boolean {
+  return p.ownerId == null
+}
+
+/** Category filter value: a specific category, or 'all'. Shared by the catalog
+ *  page and the PlantPicker so their chip rows and filtering stay in sync. */
+export type CategoryFilter = PlantCategory | 'all'
+
+/** Filter a plant list by a name query (case-insensitive substring) and
+ *  category. The single source of truth for both the /plants grid and the
+ *  PlantPicker list. */
+export function filterPlants(plants: Plant[], query: string, category: CategoryFilter): Plant[] {
+  const q = query.trim().toLowerCase()
+  return plants.filter(
+    (p) => (category === 'all' || p.category === category) && (q === '' || p.name.toLowerCase().includes(q)),
+  )
+}
+
+const plantsKey = ['plants'] as const
+
+export const plantsQueryOptions = queryOptions({
+  queryKey: plantsKey,
+  queryFn: async (): Promise<Plant[]> => z.array(plantSchema).parse(await api.get('/plants')),
+})
+
+export function usePlants() {
+  return useQuery(plantsQueryOptions)
+}
+
+export interface PlantInput {
+  name: string
+  category: PlantCategory
+  spacingCm: number
+  color: string
+  icon: string
+  daysToMaturity: number | null
+  notes: string
+}
+
+export function useCreatePlant() {
+  const qc = useQueryClient()
+  return useMutation({
+    mutationFn: async (input: PlantInput): Promise<Plant> => plantSchema.parse(await api.post('/plants', input)),
+    onSuccess: () => qc.invalidateQueries({ queryKey: plantsKey }),
+  })
+}
+
+export interface PlantUpdate extends PlantInput {
+  id: number
+  version: number
+}
+
+export function useUpdatePlant() {
+  const qc = useQueryClient()
+  return useMutation({
+    // id/version travel with the mutation variables so a single hook serves any row.
+    mutationFn: async ({ id, ...body }: PlantUpdate): Promise<Plant> =>
+      plantSchema.parse(await api.patch(`/plants/${id}`, body)),
+    onSuccess: () => qc.invalidateQueries({ queryKey: plantsKey }),
+  })
+}
+
+export function useDeletePlant() {
+  const qc = useQueryClient()
+  return useMutation({
+    mutationFn: (id: number) => api.delete(`/plants/${id}`),
+    onSuccess: () => qc.invalidateQueries({ queryKey: plantsKey }),
+  })
+}
+
+/**
+ * If err is a 409 version conflict, return the fresh server row it carries
+ * (under `current`), so a form can rebase onto it; otherwise null.
+ */
+export function conflictPlant(err: unknown): Plant | null {
+  if (err instanceof ApiError && err.isConflict && err.body && typeof err.body === 'object') {
+    const parsed = plantSchema.safeParse((err.body as { current?: unknown }).current)
+    if (parsed.success) return parsed.data
+  }
+  return null
+}

web/src/lib/units.test.ts

@@ -1,5 +1,14 @@
 import { describe, expect, it } from 'vitest'
-import { cmFromFtIn, cmFromMeters, displayFromCm, formatCm, formatDimensions } from './units'
+import {
+  cmFromFtIn,
+  cmFromMeters,
+  cmFromSpacing,
+  displayFromCm,
+  formatCm,
+  formatDimensions,
+  formatSpacing,
+  spacingFromCm,
+} from './units'
 
 describe('cm conversions', () => {
   it('feet+inches → whole cm', () => {
@@ -42,3 +51,21 @@ describe('formatCm', () => {
     expect(formatDimensions(122, 244, 'imperial')).toBe('4′ 0″ × 8′ 0″')
   })
 })
+
+describe('plant spacing (small scale)', () => {
+  it('formats cm in metric, whole inches in imperial', () => {
+    expect(formatSpacing(15, 'metric')).toBe('15 cm')
+    expect(formatSpacing(15, 'imperial')).toBe('6″') // 15/2.54 = 5.9 → 6
+    expect(formatSpacing(30, 'imperial')).toBe('12″')
+  })
+
+  it('parses an entered value back to whole cm', () => {
+    expect(cmFromSpacing(15, 'metric')).toBe(15)
+    expect(cmFromSpacing(6, 'imperial')).toBe(15) // 6in = 15.24 → 15
+  })
+
+  it('prefills an input from cm', () => {
+    expect(spacingFromCm(15, 'metric')).toBe(15)
+    expect(spacingFromCm(30, 'imperial')).toBe(11.8) // 30/2.54 = 11.81 → 11.8
+  })
+})

web/src/lib/units.ts

@@ -68,3 +68,29 @@ export function formatDimensions(widthCm: number, heightCm: number, unit: UnitPr
 export function dimensionUnitLabel(unit: UnitPref): string {
   return unit === 'imperial' ? 'ft' : 'm'
 }
+
+// --- Plant spacing (small scale) -------------------------------------------
+// Plant spacing is a handful of centimeters, so meters/feet read poorly here;
+// metric shows cm and imperial shows whole inches.
+
+/** Centimeters → a spacing string in the given unit (e.g. "15 cm" or "6″"). */
+export function formatSpacing(cm: number, unit: UnitPref): string {
+  if (unit === 'imperial') return `${Math.round(cm / CM_PER_INCH)}″`
+  return `${Math.round(cm)} cm`
+}
+
+/** A spacing value typed in the given unit (cm, or inches) → whole centimeters. */
+export function cmFromSpacing(value: number, unit: UnitPref): number {
+  return unit === 'imperial' ? Math.round(value * CM_PER_INCH) : Math.round(value)
+}
+
+/** Centimeters → a spacing number in the given unit, for prefilling an input.
+ *  Inches to 0.1 so cm-quantization doesn't show through. */
+export function spacingFromCm(cm: number, unit: UnitPref): number {
+  return unit === 'imperial' ? Math.round((cm / CM_PER_INCH) * 10) / 10 : Math.round(cm)
+}
+
+/** The spacing input-field unit label. */
+export function spacingUnitLabel(unit: UnitPref): string {
+  return unit === 'imperial' ? 'in' : 'cm'
+}

web/src/pages/PlantsPage.tsx

@@ -1,5 +1,134 @@
-import { PageStub } from '@/components/PageStub'
+import { useMemo, useState } from 'react'
+import { Alert } from '@/components/ui/Alert'
+import { Button } from '@/components/ui/Button'
+import { fieldControlClass } from '@/components/ui/field'
+import { toast } from '@/components/ui/toast'
+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 { PlantPicker } from '@/editor/PlantPicker'
+import { filterPlants, usePlants, type CategoryFilter, type Plant } from '@/lib/plants'
+import type { UnitPref } from '@/lib/units'
+
+// Which modal is open, if any. edit/duplicate/delete carry the target plant.
+type Dialog =
+  | { kind: 'create' }
+  | { kind: 'edit'; plant: Plant }
+  | { kind: 'duplicate'; plant: Plant }
+  | { kind: 'delete'; plant: Plant }
+  | { kind: 'picker' }
+  | null
+
+// There's no per-user unit preference server-side (only per-garden), so the
+// catalog page keeps its own, persisted locally.
+const UNIT_KEY = 'pansy:unit-pref'
+function loadUnit(): UnitPref {
+  try {
+    return localStorage.getItem(UNIT_KEY) === 'imperial' ? 'imperial' : 'metric'
+  } catch {
+    return 'metric'
+  }
+}
 
 export function PlantsPage() {
-  return <PageStub title="Plants">The plant catalog arrives in issue #13.</PageStub>
+  const plants = usePlants()
+  const [unit, setUnit] = useState<UnitPref>(() => loadUnit())
+  const [query, setQuery] = useState('')
+  const [category, setCategory] = useState<CategoryFilter>('all')
+  const [dialog, setDialog] = useState<Dialog>(null)
+  const close = () => setDialog(null)
+
+  function toggleUnit() {
+    setUnit((u) => {
+      const next: UnitPref = u === 'metric' ? 'imperial' : 'metric'
+      try {
+        localStorage.setItem(UNIT_KEY, next)
+      } catch {
+        // Preference is a nicety; ignore storage failures.
+      }
+      return next
+    })
+  }
+
+  const all = useMemo(() => plants.data ?? [], [plants.data])
+  const filtered = useMemo(() => filterPlants(all, query, category), [all, query, category])
+
+  return (
+    <section>
+      <div className="flex flex-wrap items-center justify-between gap-3">
+        <h1 className="text-2xl font-semibold tracking-tight">Plants</h1>
+        <div className="flex items-center gap-2">
+          <Button variant="ghost" onClick={() => setDialog({ kind: 'picker' })}>
+            Try the picker
+          </Button>
+          <Button
+            variant="ghost"
+            onClick={toggleUnit}
+            title="Toggle spacing units"
+            aria-label={`Spacing units: ${unit === 'metric' ? 'metric' : 'imperial'}`}
+          >
+            {unit === 'metric' ? 'cm' : 'in'}
+          </Button>
+          <Button onClick={() => setDialog({ kind: 'create' })}>New plant</Button>
+        </div>
+      </div>
+
+      <div className="mt-4 flex flex-col gap-3">
+        <input
+          type="search"
+          value={query}
+          onChange={(e) => setQuery(e.target.value)}
+          placeholder="Search plants by name…"
+          aria-label="Search plants"
+          className={fieldControlClass}
+        />
+        <div className="pb-1">
+          <CategoryChips value={category} onChange={setCategory} />
+        </div>
+      </div>
+
+      <div className="mt-5">
+        {plants.isPending && <p className="text-sm text-muted">Loading the catalog…</p>}
+        {plants.isError && <Alert>Could not load the plant catalog. Please refresh.</Alert>}
+
+        {plants.isSuccess && filtered.length === 0 && (
+          <div className="rounded-xl border border-dashed border-border p-10 text-center">
+            <p className="text-fg">No plants match.</p>
+            <p className="mt-1 text-sm text-muted">Try a different search or category, or add a custom plant.</p>
+          </div>
+        )}
+
+        {filtered.length > 0 && (
+          <div className="grid grid-cols-1 gap-4 sm:grid-cols-2 lg:grid-cols-3">
+            {filtered.map((p) => (
+              <PlantCard
+                key={p.id}
+                plant={p}
+                unit={unit}
+                onEdit={() => setDialog({ kind: 'edit', plant: p })}
+                onDelete={() => setDialog({ kind: 'delete', plant: p })}
+                onDuplicate={() => setDialog({ kind: 'duplicate', plant: p })}
+              />
+            ))}
+          </div>
+        )}
+      </div>
+
+      {dialog?.kind === 'create' && <PlantFormModal unit={unit} onClose={close} />}
+      {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 === 'picker' && (
+        <PlantPicker
+          unit={unit}
+          onClose={close}
+          onSelect={(p) => {
+            toast.info(`Picked ${p.name}`)
+            close()
+          }}
+        />
+      )}
+    </section>
+  )
 }