Plant good neighbors

In the States, we call it "companion planting." In France, it's known by the more neutral term, "associations des plantes". A reader of this web site heard it referred to as "French Infusion gardening," which, being a journalist myself, sounds to me like a journalist's sexy new title for an old topic.

Old and venerable it may be, but the idea that some plants mutually benefit by being planted adjacent to each other is firmly rooted in French gardening tradition. In fact, this notion is at the very heart of the justly famous French flowering potager or vegetable garden. A potager here in France is just about never without some intermingled flowers. While to the casual observer, this may seem like just an expression of the French appreciation for beauty (and it partly is), it actually has much deeper roots than simple good looks.

The idea of comingling food plants with flowers dates from the era long before garden chemicals were available. Moreover, it originated in a time when French people depended almost entirely on their vegetable and fruit plot for the vegetal portion of the family diet. Over the centuries, French gardeners noticed that certain flowers or herbs, planted next to certain vegetables or fruits, seemed to stimulate the food plant's growth or production. Additionally, they noticed that certain crops planted adjacent to each other seemed to enhance each other's growth, while others did more poorly when planted in proximity.

Like many folk wisdoms, the tenets of companion planting are beginning to be substantiated by modern scientific observation. In fact, this ancient practice is highly beneficial. There exists no single, simple explication for its efficacity, but rather a web of inter-related reasons which mirror the ecological web of the organic garden itself.



First and foremost, the presence of flowers in the vegetable garden attracts pollinating insects, necessary for the production of all vegetables which are actually fruits (botanically speaking), including tomatoes, beans, peas, eggplants, peppers, and the like. Thus, the traditional inclusion of dahlias, which are great attractors of bees and butterflies, in the French potager, undoubtedly originated from this intuitive observation.



Second, many flowers and especially herbs have aromas that either directly repel insects or mask the scent of their target plant so that they can't find it and eat it. That is the case for the purple sage, planted in beautiful color harmony with the purple cabbage at right, and likewise for the strong-smelling purple-leaved perilla (below), which helps ward pests away from the 'Red Kuri' squash that is its neighbor, while maintaining the oriental them of this particular potager.



The plant most well-known for its pest-repelling abilities is probably the marigold. It has been well-documented that repeated planting of marigolds repels harmful soil nematodes which feast on the roots of garden plants. Because these nematodes are most destructive to tomatoes, marigolds are a time-honored companion to these garden favorites.



The gardeners in the communal organic potager at Le Manoir de Fay, not far from us in Normandy have taken this idea one step further. In the photo at right, you'll notice that the marigolds at the feet of the tomato plants are alternated with another helpful companion: comfrey (Symphytum officinale). In France, comfrey is believed to have many "medicinal" effects on other garden plants, many of which are beginning to be documented. Among others, comfrey helps reduce fungal diseases in tomatoes. Even a mulch of comfrey leaves is beneficial, not only to tomatoes, but to roses and other fungus-prone plants as well.

Garlic is often planted around roses in by French gardeners, who say that it repels red spider mites and also gives their roses a more intense color and fragrance. Tomatoes near roses help reduce blackspot on the latter.

However, just as with herbal medicines for humans, herbal plant medicines are not to be used carelessly. Marigolds, for instance, may be beneficial to nematode-prone plants in areas where nematodes are a problem. However, they can also have allelopathic effects on many herbaceous flowering plants, so they should not be freely intermingled throughout your flower borders. Allelopathy is a plant's secretion into the soil of compounds that inhibit the growth of other plants.



The common biennial foxglove (Digitalis purpurea), on the other hand, has traditionally been allowed to self-sow throughout French gardens because of its beneficial effects on other plants. It is believed to stimulate their growth and enhance their resistance to disease. In addition, it is said to enhance the keeping qualities of fruits and vegetables it grows among. Whether this has ever been investigated scientifically, I don't know. But for French gardeners, the word of experience is sufficient reason to perpetuate the tradition.



In French gardens and orchards, nasturtiums are almost always planted as a trap plant for aphids. Aphids prefer nasturtiums to just about all other plants, and so gravitate to them, leaving other plants alone. The nasturtiums, on the other hand, seem to have worked out a truce with the aphids, because they just go on growing and flowering. In the photo at right, aphids are planted at the foot of espaliered apple trees for that very reason.

The blossoms of many herbs and wildflowers are enormously beneficial to any garden in that they attract an abundance of beneficial insects that prey on pest bugs. Letting your coriander and dill go to flower is not only aesthetically pleasing, but has very remarkable pest-control benefits as well. The same is true of Queen Anne's lace, coreopsis, and hosts of other wild plants.

Finally, most mysterious of all, some plants simply seem to flourish better in each other's company, while others grow more poorly than normal. Scientific observations show that good companions literally entwine their roots so that underground, the two different plants present one indistinguishable mass. On the contrary, plants which seem to inhibit each other's growth "turn their backs" on each other underground: their respective roots keep as far apart from each other as possible, leading of course, to less root growth altogether. It has also been substantiated that good companions exhibit markedly more proliferation of root hairs--the very fine rootlets that are responsible for actually absorbing nutrients from the soil--when grown together than apart.

Some plants make good neighbors to others because they draw certain nutrients toward the surface of the soil, making them available to their neighbors. This is why chamomile is such a good companion to many plants.

Following is a partial list of garden plants with their "good" and "bad" neighbors:

Garlic
Good neighbors--strawberries, cucumbers, raspberries, lilies, carrots, tree fruits, roses, beets, tomatoes, tulips
Bad neighbors--peas, cabbage, pole beans

Asparagus
Good neighbors--cucumbers, lettuce, parsley, tomatoes
Bad neighbors--garlic, onions

Beets
Good neighbors--bush beans,dill, cucumbers, garlic, cabbages, coriander, cumin, lettuces, summer squash, onions
Bad neighbors--potatoes, leeks, corn, spinach

Carrots
Good neighbors--Dill, peas, garlic, leeks, chard, radishes, rosemary, sage, chives, lettuces, salsify, tomatoes, chicory, onions
Bad neighbors--None

Celery
Good neighbors--Bush beans, cucumbers, chamomile, cabbage family, leeks, tomatoes
Bad neighbors--potatoes, lettuces, corn

Cabbage family
Good neighbors--artemisias, beans, dill, endive, peas, chamomile, potatoes, lettuce, coriander, cumin, leeks, chard, mint, beets, celery, spinach, tomatoes
Bad neighbors--strawberries, muistard, garlic, onions

Cucumbers
Good neighbors--Beans, dill, peas, fennel, catnip, cabbage, lettuce, coriander, cumin, leeks, corn, beets, celery, onions
Bad neighbors--radishes, tomatoes

Squash
Good neighbors--nasturtium, corn, beets, pole beans, onions
Bad neighborsnone

Spinach
Good neighbors--Strawberries, potatoes, cabbage, radishes, celery, pole beans, tomatoes
Bad neighbors--none

Beans
Good neighbors--Winter savory, strawberries, cucumbers, potatoes, cabbage, lettuce, beets, celery, tomatoes
Bad neighbors--Peas, fennel, garlic, leeksn, onions

Cutting lettuces
Good neighbors--dill, fennel, cabbage, radishes, beets, salsify, asparagus, tomatoes
Bad neighbors--none

Heading lettuces
Good neighbors--Beans, dill, peas, strawberries, fennel, cucumbers, chervil, cabbages, cress, leeks, corn, carottes, mint, radishes, beets, salsify, asparagus, tomatoes, chicory, onions
Bad neighbors--Parsley, celery

Corn
Good neighbors--Beans, cucumbers, potatoes, lettuces, squash, melons, tomatoes
Bad neighbors--Beets, celery

Onions
Good neighbors--Winter savory, dill, strawberries, cucumbers, chamomile, lettuce, carrots, beets, salsify, chicory
Bad neighbors--Beans, peas, cabbages

Leeks
Good neighbors--endives, strawberries, chamomile, cabbages, lettuce, carrots, salsify, celery, tomatoes
Bad neighbors--Beans, peas, beets

Peas
Good neighbors--dill, fennel, cucumbers, cabbages, lettuce, corn, carrots, radishes, squash
Bad neighbors--Beans, potatoes, leeks, tomatoes, onions

Potatoes
Good neighbors--Favas, chamomile, nasturtium, cabbages, cumin, corn, horseradish, mint, spinach, marigolds
Bad neighbors--Peas, squash, beets, celery, tomatoes

Tomatoes
Good neighbors--beans, nasturtium, garlic, cabbages, lettuce, leeks, corn, carrots, parsley, lettuce, radishes, beets, celery, spinach, chicory
Bad neighbors--peas, fennel, potatoes

Companion planting is an absolutely wholistic concept. It operates on many levels in a complex, web-like fashion which is truly ecologic. And it fits into the ecology of the gardener as well, because a well-associated garden is also much more beautiful, full of flowers, contrasting foliages, and beneficial insect life. Bethann, this one's for you.

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Products of Interest:
French wildflower seed mix--'Belles Estivales'
French wildflower seed mix--'Prairie Fleurie'
French wildflower seed mix--'Woodland Edge'
French wildflower seed mix--'Fleurs des Champs'