Castor Bean
Also known as: Ricinus communis · Castor Bean · Castor Oil Plant
Deadly poisonous
When & where
Germination
Spacing & depth
How to plant
Soak large seeds overnight, then sow in warm moist mix. Keep at 75°F until sprouting. Transplant after frost danger passes.
Grower's tip
Fast-growing tropical-looking annual with large palmate leaves. All parts especially seeds are highly toxic if ingested.
Woody plant facts
Good to know before you grow this
Parts of this plant are toxic to people and pets — don't eat it and keep it away from children and animals.
Soil preferences
Free-draining garden soil. Most shrubs fail from wet feet, not poor fertility.
5.5–7.0 for most; acid-lovers (rhododendron, blueberry) want 4.5–5.5.
Mulch a wide ring with compost or bark each spring; keep mulch off the stems.
Watering
Deep soak weekly for the first two seasons, then only in drought.
Slow soak over the root zone, not the crown.
Overwatered: yellowing leaves, dieback, sour soil. Underwatered: leaf scorch, early leaf drop, sparse bloom.
Prefers top-watering — Top-water only — deep slow soak at the drip line, never at the trunk. Bottom-watering is only for tree seedlings in nursery pots (shallow tray 15 min). Established trees always get watered from above onto the soil.
Temperature tolerance
Broad — hardy shrubs handle 35–90°F once established
Down to the species' rated zone minimum
Hardy once established; first-winter seedlings need a mulch collar or cold frame.
Special germination requirements
Most temperate tree seed needs cold stratification (30–120+ days at 34–41°F) — see each species entry for the exact time.
Container growing
Possible with the right cultivar
10–20 gal (38–76 L) for a long-term potted shrub
Dwarf and compact forms do fine in large pots; full-size shrubs eventually need the ground.
Detailed harvesting
Nothing here is harvested for the kitchen. Wear gloves for any cutting or deadheading, keep the sap off your skin and eyes, and wash your hands and tools afterwards.
Post-harvest storage & preservation
Do not dry, store or preserve any part of this plant near food. Bag prunings for the bin — never compost them where animals browse, and never burn them.
Culinary, medicinal & other uses
Ornamental only — this plant is poisonous and has no food, tea or home-remedy use. Grow it for looks, wear gloves, and keep it away from children, pets and livestock.
Medicinal or traditional uses are shared for interest only — this is not medical advice. Consult a qualified professional before using any plant medicinally.
Seed saving
Mostly insect-pollinated; seedlings vary from the parent.
Not practical. Named cultivars must be grown from cuttings, not seed.
Collect ripe seed or clean berries in fall, then cold-stratify before spring sowing.
Your zone's planting calendar
Pick your USDA hardiness zone and we'll estimate the key dates for castor bean in your area. These are regional averages — always check your own last-frost forecast before sowing.
My Castor Bean notes
Castor Bean seeds on hand
Track packets and loose seeds you already have. Private to your account.
Par level — leave at 0 for no alert. Anything below par shows on Seed Starting and your shopping list.
Order more seeds
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