Last year I harvested almost nothing from my vegetable garden.  I blamed my disappointment mostly on the family of woodchucks who had moved in--so cute but so destructive--and the squirrels, raccoons, and skunks who helped themselves to whatever bits the woodchucks overlooked.  (I think there is electric fencing in my future.)  I blamed myself, too: not enough compost, not enough watering, not enough weeding.  Well, after all, I did get a new hip last summer.  As I’ve learned recently, though, there may have been yet another culprit: the plants themselves.  Or, rather, their positions in the beds.

 

Most gardeners learn fairly early on about the benefits of companion planting.  The right plants can repel harmful insects, provide shade or structural support, and suppress weeds.  Marigolds make a vegetable garden bright and pretty, while also deterring pests, zinnias attract pollinators, and nasturtiums lure caterpillars from food crops.  Basil repels thrips and tomato hornworm moths, while garlic repels aphids.  Borage attracts pollinating bees, and dill attracts ladybugs.

 

The most famous example of companion planting, as well as one of the oldest, is the “Three Sisters” of Native Americans.  Instead of planting in neat rows, indigenous people planted corn, beans and squash all together.  Cornstalks provided a ready-made support for climbing bean vines; beans fixed nitrogen in the soil, for the benefit of anything growing there; and the sprawling squash shaded the ground around the base, suppressing weeds.  Planted together, this trio is so well balanced that the same patch remains productive for 25 years, instead of the paltry season or two soil remains healthy when conventional methods are used.

 

Less well known, and maybe less researched, are the plants which, grown too close together, can harm each other.  Some are allelopathic, a tongue twister that translates to outright biological warfare, as these plants send out toxic chemicals to suppress germination and growth.  The best-known is black walnut trees, which are notorious for preventing anything else from growing nearby.  Luckily, you’re probably not growing full-size trees in the middle of your vegetable garden.

 

You’re far likelier to have sunflowers, which are great sources of pollen for insects and, later, seeds for birds, but also resent close neighbors: thanks to dropped sunflower seeds, there’s probably a dead spot under your bird feeder.  Plant them, for sure, but in a corner by themselves where they can’t cause mischief.

Onions can be bad neighbors for asparagus and beans, inhibiting growth.  Brassicas, like broccoli and cabbage, interfere with members of the nightshade family, notably tomatoes and peppers.  And fennel fights with almost everything, even as it hides its combative nature behind delicate feathery fronds.  Garlic repels some pests, but stunts the growth of peas, asparagus, beans and strawberries.  I didn’t plant any last fall, thanks to that new hip, and since garlic is best planted in late fall, it shouldn’t interfere with this summer’s crops.

 

Even when plants aren’t overtly hostile, planting them together can still produce disappointing results.  This may be due to competing demands for the same nutrients, or shared susceptibility to the same pests.   Squash and cucumbers are both heavy feeders and will quickly exhaust nutrients in the soil.  Potatoes and zucchini will also compete—and the potatoes will probably win.  And if you like weird outcomes, try interplanting pumpkins, a winter squash, with summer squashes.  The two may cross-pollinate, producing strange-looking and peculiar-tasting hybrids.

 

Sometimes you can turn potential pitfalls to your advantage.  When a green and healthy squash vine shrivels up overnight, the culprit is the squash vine borer.  The female deposits her eggs on the plants, and when they hatch, the revolting white offspring bore into the vine.  As they travel upward they push out sawdust-like excrement, or “frass,” while inside they’re tunnelling through and destroying the plant’s arteries.  All squashes are susceptible, but you may be able to limit the damage with a decoy.  Farmers have been known to plant blue hubbard squash, a squash borer favorite, around the perimeter of a field, sacrificing it in order to spare the butternut squash in the middle.  If you have enough space, you could try this strategy too.

 

So, yet another level has been added to the three-dimensional chess game that masquerades as a simple vegetable garden plan.  After I sort the start dates, from early peas and lettuces through to wait-until-the soil-is-warm tomatoes: after I determine which need full sun and which partial shade, which need trellises and which room to sprawl; after I plan for an annual rotation; and after I amend the soil and finally install some drip irrigation, I still won’t be ready to plant until I check my layout against companion planting suggestions AND an enemies list.  I’ll have a bumper crop this year—even if I have to share it with the woodchucks.

 

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