Last week, reading about the importance of plant species diversity in ecosystems, it occurred to me that biodiversity is also an important consideration in planning the vegetable garden, that the wise gardener will avoid monoculture, or the planting of large expanses of a single crop, in favor of mixed plantings. Instead of setting the table for insects and diseases by planting entire beds or rows to a single crop, you can grow a diverse mix of compatible species within each bed or row and thus minimize pest problems in the garden.
I mentioned this to Marjorie, an expert on such matters, and she placed in my hands a well-used copy of “High-Yield Gardening” by M.B. Hunt and B. Bortz, 1986, Rodale Press. In it I found validation for this thinking in the chapter on interplanting, in which they state that interplanting schemes, through their diversity, “create complex ecosystems that imitate the rich mosaic of nature and therefore encourage spiders, toads and other valuable insect predators and discourage the spread of crop-specific pests and diseases.”
The vegetable garden as an ecosystem — what a grand idea. It brought to mind the family of spiders we found a few summers ago among the snow peas, a web filled with a hundred tiny babies swarming around their mother.
In interplanting, two or more crops are grown at the same time in one bed. While each planting yields less than it would if grown alone, the total yield is greater than would be achieved with monoculture, but only if compatible crops are chosen.
Interplanting combinations should focus on both aboveground and below-ground compatibility. Plants that complement one another in the shape of their top growth will fill the available garden space, leaving no room for weeds to grow. Corn and beans, for example, when grown together, intercept 90 percent of the available sunlight. They are also an ideal couple as far as underground compatibility, since corn is a shallow rooting crop while beans have deeper root systems.
Interplanting schemes should also take nutrient sharing into account, mixing heavy feeders with light feeders. Fortunately, most interplanting schemes designed for sharing of aboveground and underground space also result in efficient nutrient sharing.
Imagine the mosaic of green in garden space shared by interplanted Brussels sprouts, parsley and spinach; a bed with plants of peppers, basil and tomato arranged in an alternating pattern; a mixture of radishes, lettuce and peppers filling a bed from edge to edge; or a mixed bed of lettuce and cabbage bordered by trellised peas. Some gardeners go so far as to transplant cabbage seedlings among the strawberries after the berry harvest is done.
Some interplanting schemes happen by chance. Last season, from June until hard freeze in Marjorie’s garden, volunteer calendulas flowered cheerfully beneath peas and around the squash plants. The bright yellow and orange flowers attracted native bees that provided pollination service to both calendula blooms and vegetable crops.
Many gardeners are drawn to interplanting as a technique for maximizing the use of garden space, and indeed this is one of the benefits. More important, I think, is the integration of this method of vegetable gardening into the ecological landscape. I keep thinking about those spiders in the snow peas.
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Vegetable combinations for interplanting:
Beans – corn
Corn – squash, melons, cucumbers
Beans – corn – squash, melons, cucumbers
Leeks – carrots
Beans – radishes
Leeks – parsley
Cabbage – chives
Lettuce – carrots – onions
Cabbage – peppers
Lettuce – onions
Cabbage – squash, melons, cucumbers
Lettuce – radishes
Cabbage – tomatoes
Melons – radishes
Cole crops – tomatoes
Onions – cabbage
Corn – cabbage
Onions – peppers
Corn – lettuce
Onions – spinach
Peas on trellis – cole crops, turnips, lettuce, carrots, spinach