When you want a big, fast-growing plant, castor bean is the one to choose. This annual (grows just one year) sprouts into a tall plant with large, exotic leaves up to 90 cm (3 feet) across.
Sow castor bean from seed either outdoors directly in the soil after all danger of frost has passed or indoors six to eight weeks before your region's last average frost date.
Soak the seed for 24 hours in warm water, then plant it 2.5 cm (1 inch) deep.
Plant outdoors in full sun. Castor bean needs rich, deep, well-drained soil, so it's a good idea to work in a spadeful or two of compost to a depth of 60 cm (2 feet) or more.
Keep soil evenly moist. Mulching is a good idea.
Trim faded flowers to promote longer bloom.
Fertilise every four to six weeks or work in a slow-release fertiliser (or plenty of compost) at planting time.
Stake if needed. Castor bean grows 90 to 180 cm (3 to 6 feet) tall, depending on growing conditions, and 60 to 120 cm (2 to 4 feet) wide.
True to its tropical nature, castor bean loves heat and humidity and does best in regions where both are ample. Foliage may be green, blue-gray, deep purple or brown.
Castor bean seeds are highly poisonous, so keep children away from seedpods developing on plants. (Some gardeners remove and discard the seedpods for this very reason.) Sap from seeds and the plant may cause an allergic reaction, so handle seeds with care, and touch these plants only while wearing long sleeves and gardening gloves.