Dawn Pettinelli: Castor bean plants can give garden a tropical touch

Dawn Pettinelli: Castor bean plants can give garden a tropical touch

The Westerly Sun


Decorative palmate leaves on large, lanky plants give castor beans a distinctive tropical look to gardens and containers. I began growing them around a wellhead after receiving anecdotal evidence that these plants repel voles. Apparently, Thomas Jefferson grew them for the same purpose. The plants themselves were not much of a vole deterrent, but the oil is made into a product that is sold today as a rodent repellent.

Their tropical look paired so well with late flowering, single-pink mums, large-leaved cannas, trailing nasturtiums, and pots of broad-leaved agapanthus and amaracrinums that I just replant castor beans each year. Never have they had any insect or disease problems and this may well be because ricin, a deadly poison, is found throughout the plant.

This sounds much worse than it really is. This compound is mainly concentrated in the seeds, and oils from the seeds are pressed and distilled without harmful consequences. Castor oil is used for cosmetics, lubricants, pigments, plastics, waxes, pharmaceuticals and other products. During processing, the poisonous compound is insoluble in oil and therefore remains in the pomace during pressing. Older readers may recall a disagreeable dose of castor oil being administrated to them as young children.

Some considerations, however, should be taken into account in growing castor beans in backyard gardens. The plant is in the Euphorbia family, the same as poinsettias, and both plants can cause contact dermatitis in sensitive people who touch them. None of my gardening friends have had any skin issues because of this plant, but if you are worried that children or pets might eat the seeds, simply remove the flowers that are forming this month, so no seeds will be produced. The seeds are the most poisonous part of the plant. The flowers are interesting but not very decorative.

In the tropics, plants may reach up to 40 feet tall. In my garden, they seldom get taller than 6 to 8 feet before the frost cuts short their lives, but in the southern part of Connecticut in a good year they may reach 10 feet or more. The huge leaves may be green or reddish in color, depending on the cultivar that is planted, and can be 1 to 2 feet wide. They have 5 to 9 toothed lobes and add a great deal of texture to the garden bed. Dwarf varieties, like Impala, can be placed in tubs or other large containers.

Castor beans really enjoy hot, humid summers. Place plants in full sun and make sure they get adequate water while becoming established. Pair the red leaf varieties with cool pink, purple or blue flowering annuals or perennials. The green leaf sorts combine nicely with hot red, gold and orange-colored flowers. The description of these towering plants with hefty leaves is a bit misleading as they tend to be more open and thus allow in more light than one might think. Because of this trait, they can be underplanted to some degree or at least be expected to share the garden bed. Around my wellhead they are planted among a bed of single, clear pink mums and the combination of the burgundy castor bean leaves surrounded by pure pink mum blooms is really quite lovely — at least until the first hard frost hits.

The large seeds can be started indoors in April for transplanting outside around Memorial Day. They are generally fairly easy to start indoors and are attractively speckled, although some have compared their appearance to engorged dog ticks. If you only need a plant or two, seek out a local nursery and buy transplants.

For those looking for that tropical touch, especially in late summer when thoughts turn to autumn leaves, school supplies and apple picking, consider where you could plant a castor bean or two. The plants are sure attention getters and September is prime time to luxuriate in their exotic exuberance before that long, cold winter sets in.

For questions on castor beans or on other gardening topics, feel free to contact us at the UConn Home & Garden Education Center at 877-486-6271, visit our website at www.ladybug.uconn.edu or contact your local cooperative extension center.






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