Castor oil plant
Also known as
Castor bean, Palma Christi, Wonder tree, Higuerilla, Mamona
Keep this plant’s care guide close at hand.
Get the appAbout Castor oil plant
Ricinus communis, commonly called the castor oil plant, is a fast-growing, heat-loving species valued for its dramatic, palmately lobed leaves and architectural presence. Plants can reach 1–4 meters in a single season in warm climates, with cultivars displaying green, bronze, purple, or burgundy foliage. Spiny, spherical capsules follow inconspicuous flowers and contain highly toxic, beautifully mottled seeds rich in castor oil; ingestion of raw seeds is extremely dangerous due to ricin. Native to parts of Africa and the Mediterranean region, it is now widely naturalized across tropical and subtropical areas and grown as an annual in temperate zones. It thrives in full sun and fertile, well-drained soils, tolerating heat and short dry spells once established. While castor oil has industrial and medicinal applications, the plant’s sap may irritate skin, and all parts—especially seeds—must be kept away from children and pets. In some regions it behaves invasively, so check local guidance before planting and deadhead to prevent unwanted self-seeding.
Taxonomy
Properties & Requirements
How to care for Castor oil plant
Water
Keep soil evenly moist for the first 4–6 weeks to establish deep roots, watering deeply rather than frequently. Once established, water when the top 3–5 cm of soil dries; weekly deep irrigation usually suffices, increasing during extreme heat or in sandy soils. Avoid waterlogging—roots resent standing water. Container plants dry faster and may need watering every 1–3 days in summer. Mulch to moderate evaporation, and always water at the base to keep foliage dry.
Light
Provide full sun for best vigor and richest foliage color—at least 6–8 hours of direct light daily. In very hot climates, light afternoon shade can reduce leaf scorch without sacrificing growth. Insufficient light leads to lanky stems and dull coloration, especially in dark-leaved cultivars. Indoors it performs poorly due to size and light demands and is not recommended. Avoid deep shade or crowded plantings that block sun and airflow.
Nutrients
In fertile ground, mix compost or well-rotted manure before planting. For vigorous seasonal growth, apply a balanced granular fertilizer (e.g., 10-10-10) at planting and side-dress midseason. Container-grown plants benefit from a dilute balanced liquid feed every 2–3 weeks during active growth. Emphasize nitrogen early for leaf expansion, then maintain with balanced nutrients. Avoid over-fertilizing, which can cause weak, lush growth; always water in fertilizers to prevent root burn.
Temperature
A warm-season plant, Ricinus communis thrives between 20–32°C and is very frost sensitive. Plant outdoors only after all danger of frost has passed and night temperatures are consistently above 10–12°C. Growth slows markedly below 10°C, and frost will kill top growth. Perennial in USDA zones 9–11, it is typically grown as an annual elsewhere. Full sun, heat, and good air movement promote sturdy growth; provide wind protection in exposed sites.
