Castor plants are lovely to look at – and castor sure love our hot summers in the Southwest! Some people are afraid to plant them because the seeds can be toxic if crushed open and ingested, but if you don’t plan on eating them, you can plant them along the south facing wall of your home for some summer shade.
Castor is Tropical
Castor (Ricinus communis) is originally from the southeastern Mediterranean Basin and Eastern Africa, but is widespread throughout tropical regions, and widely grown in warm climates as an ornamental plant. The seeds yield castor oil, which has a wide variety of uses, including in cosmetics. The issue with castor seeds is that they also contain ricin, a water-soluble toxin. Ricin is also present in lower concentrations throughout the plant.
Castor is Ornamental
In the tropics, castor plants can attain the height and stature of a tree, up to 40 feet tall. The plants are very sensitive to cold though, so it is mostly planted as an ornamental annual that can get 8 to 10 feet tall.
Castor plants are striking ornamentals. They can vary greatly in growth habit and appearance. The variability has been increased by breeders who have selected a range of cultivars for leaf and flower colors, including scarlet, bronze, or maroon leaves, topped by large, decorative seed pods in shades of red, orange, or maroon. Plants make an excellent temporary screen or exotic backdrop for the back of the garden border.
Growing Castor Plants
Since they are intolerant of frost, castor plants can be started indoors and planted out once the soils warm, or planted directly in the soil in spring. (or now – in May into June). For best results, soak seeds in a moist paper towel for 24 hours before planting. The large seeds should be buried about one inch deep.
Castor plants prefer full sun and should be kept evenly moist to get growing. Plants are from tropical areas with high humidity, thus in our area, they do best in a monsoon garden. If the rains are heavy, additional water may not be required.
Soil for castor plants should be a rich garden soil. I planted some next to the citrus trees and they grew happily together.
We had a mild winter in Tucson in 2020-2021, and my castor plants overwintered in their protected area. The same can’t be said for my friends castor plants in Texas, that brutal winter freeze killed them dead. Luckily she has seed, and has already started new ones.
Harvesting and Use
It is not recommended to attempt processing of castor oil at home. But do save some seed of your plants to grow next year.
I can’t promise you this will work for you – but I tossed hands full of castor seed (still inside their stickery pods) down the holes of a ground squirrel village near my garden. Within 3 days the little ruffians appear to have abandoned that site.
More about overall care of your land and landscape in this book: Month by Month Gardening for Arizona, Nevada, and New Mexico (Cool Springs Press). This link is to Amazon and if you buy the book there the Horticulture Therapy non-profit Tierra del Sol Institute will get a few pennies – at no extra cost to you.
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