Annuals Companion planting Gardening

The Nasturtium as a Sacrificial Plant

Nasturtium leaf infested with aphids. Photo: cuckoosvegpatch.wordpress.com

In organic gardening books and web pages, the nasturtium (Tropaeoleum majus), a popular annual, is often touted as an ideal companion plant, used to repel aphids (greenflies). But that advice may do more harm than good if you stop at just planting it.

The nasturtium is actually what is known as a trap crop (also trap plant or sacrificial plant) … it doesn’t repel aphids, it attracts them! So, if you simply plant it as a companion plant, it won’t solve your aphid problem, but may in fact worsen it. That’s because once aphids settle on a nasturtium, they can easily make the jump to neighboring plants. This is especially true if there are ants in the sector (and aren’t there always?), as ants feed on aphid honeydew and literally farm them. They won’t hesitate to carry their aphid cows to the vegetables right next door, moving them to “greener pastures.”

So, the real use of the nasturtium in a vegetable garden is not as a companion plant, but as a trap crop. When you see aphids on the nasturtium, you simply have to pull it out and destroy it, nipping the infestation in the bud.

It’s a simple step, but a necessary one.

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

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