Green Side Up

Garden talk with Gazette community blogger Janice Peterson.

Castor bean plants: Giant annuals for the garden

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Janice Peterson
Monday, October 14, 2013

I always enjoy having something in my garden that makes my neighbors say "What the heck is THAT?". In the past it's been black tomatoes and pretzel bean vines. This year it's my castor bean plants, which I situated so they are easily seen from the street. These plants can grow extremely tall really fast (up to 20 feet in a season!) and their large palmate leaves give them a nice tropical look. Mine are also serving as an attractive living fence between my property and my next door neighbors.

My castor bean plants have done really well this year, despite my general lack of watering or fertilizing. (Maybe they thrive on neglect.) One has grown over 15 feet tall!

Castor bean plants (Ricinis communis) are a full sun annual here in Wisconsin. They are easily grown from seed, either directly sown into the ground after the last frost in spring or started indoors in pots. Some varieties, such as 'Zanzibariensis' grow up to 20 feet tall and 6 feet wide. Other varieties like 'Carmencita' are smaller but have wonderful burgundy leaves. I have found that generally they don't need staking, although occasionally one will need support (this is where a fencepost comes in handy). The spiky seedpods are an attractive pink or red. The seeds are very toxic, however, so if this is a concern the flowers or the seed pods can be removed.

Castor beans are used to make castor oil. Years ago many children held their noses while taking castor oil as a health supplement—luckily not anymore! The oil was safe to use because the toxin is water soluble and is destroyed by heating.

As the weather gets cooler I'll need to tear these monsters out. This is perhaps the one drawback to growing these, as it's like taking down a small tree.

Years ago I had a contest with some friends to see who could grow the tallest castor bean plant. That time I didn't even come close to winning. Darn, I wish I had challenged someone to a contest this year!

Janice Peterson has worked as a grounds horticulturist at Rotary Botanical Gardens in Janesville since 2002. She is a master gardener with the Rock Prairie Master Gardener Association. Though her education is in plant science, she considers her love of gardening and strong back to be her true qualifications. Janice is a community blogger and is not a part of The Gazette staff. Her opinion is not necessarily that of The Gazette staff or management.

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