Castor beans: A touch of the tropics

Sweltering heat and bright sunlight do not a tropical garden make, even if many common garden plants, from marigolds to okra, do hail from the tropics.

That tropical look comes from lush, bold foliage.

Cannas provide such foliage, but get off to a slow start and need the right storage conditions if the tubers are to be carried through the winter. Some gardeners create instant tropicana by planting banana trees outdoors each summer and storing them through winter indoors, chilled into a semi-sleep.

My vote for the best plant to tropicalize a garden nook is castor bean. It’s easy to grow and easy to carry on from year to year. And it grows quickly.

Castor bean is an annual, but don’t think that means it’s only going to grow a couple of feet tall by the end of the season. If you planted a castor bean seed this past May, by now you’d have a shrub or small tree 6, 7 or more feet high. The plant practically leaps out of the ground.

It does have an enormous thirst and appetite, so it needs rich soil and plenty of water.

That great thirst probably gave rise to castor beans’ alleged ability to keep moles and malaria at bay. Both scourges thrive where there is an abundance of moisture -- the moles for the earthworms that thrive in moist soil and the malaria from the resultant mosquitoes.

Castor bean plants can draw water up and out of the soil. Some gardeners try to chase off moles by dropping castor bean seeds into mole tunnels, or by watering castor oil into the ground.

Let this annual go to seed

About now, castor bean plants slow down as they channel some of their energy into making flowers and then seeds. Don’t nip out those flowers in an effort to get a plant to grow even bigger, as you might with some other annuals grown for their foliage.

The castor bean’s individual flowers are unimpressive, but they are massed in fuzzy stalks that complement the plant’s broad swaths of shiny foliage.

Those leaves can grow quite large, as much as 3 feet across. Among the many varieties of castor bean are ones with bronzy green leaves and red stems, ones with bright green leaves and white veins, and ones with blood red leaves and stems.

The darker side of castor bean

And now for the downside of castor bean. No, not castor oil, that foul-tasting fluid that was forced down the throats of our grandparents when they were ill as children.

What is ominous is that every part of the plant except for the oil is extremely poisonous. Think twice before planting castor bean if young children are around. Alert any visitor to your garden that the plant is poisonous.

This story was originally published September 29, 2011 at 12:00 AM with the headline "Castor beans: A touch of the tropics."