Rethinking plant spacing to maximize yield

“I ignore what the books say,” my friend huffed. “If I planted my vegetables as far apart as I’m supposed to, they’d be in my neighbor’s yard.”

I know what she means. In today’s small gardens the old guidelines don’t apply. If we had to grow cabbage in rows 3 feet apart, few of us would bother with it. Instead, we’ve learned to plant in blocks or wide rows, spacing the plants equidistant from one another in a grid. For some, the whole idea of the row is obsolete.

Historically, rows came into being in the days when horses began to pull seeders and cultivators and needed a place to walk. Now a narrow footpath between intensively planted areas will suffice, so that we are able to focus on how much space an individual beet, lettuce or cauliflower needs. Plant spacing is still important — an exact science, some might say — but for me it is not something for which I apply hard and fast rules. Garden math has always seemed a bit like using Mapquest to find Nirvana. Just as I’d rather cook without a recipe, I’d rather pay close attention to each variety’s needs, then space them by instinct. If I were to deconstruct what lines of thought go into such decisions they would go something like this:

Wide and tight spacing both have their virtues. With tight spacing, you can cram more into the garden. As you plant closer and closer, yields eventually diminish, but not as soon as you’d think. Research has shown that a carrot needs only 4 square inches of soil to grow well. That means you can make your rows 2 inches apart, with the carrots 2 inches apart in the row (in other words, a grid with carrots spaced 2 inches apart each way). Even the biggest lettuce head only needs a square foot. A beet might need 2 to 6 inches each way, depending on whether you want baby-sized, medium or huge. I sow mine thickly, harvest the thinnings for greens, take the small ones as needed, then leave the rest to mature for storage. Peas and beans do well with close spacing, though I’ve found climbing beans yield more if spaced regularly along the bottom of a trellis than in clusters at the base of a pole

Close planting also creates a living mulch. The thick canopy of leaves shades the ground, keeps it moist and prevents weeds from colonizing it — good for the crops and good for the busy gardener! Even in a row system, you’ll find that weeds growing in the space between rows compete more destructively with the crop than those within the rows themselves. This is because the crop shades the in-row weeds and grabs a bigger share of soil nutrients. Obviously a closely planted garden needs less fertilizer and water too.

One point at which close planting fails to pay off is where it begins to foster disease because air can’t circulate, and moisture can’t evaporate. Another is the point where it blocks sunlight. Sun is necessary for leaf crops and even more so for fruiting ones such as tomatoes and peppers. Just as importantly, close planting fails when crops are inconvenient to tend. An impenetrable stand of staked tomatoes excludes not only the sun but also the gardener. A bean jungle will never be picked. A prickly chaparral of zucchini foliage is as enticing as the evil forest in “Lord of the Rings.”

Other factors are weighed. If the soil is fertile and well-watered, you can get away with closer plantings. If you like to hoe standing up rather than crouch and pull weeds by hand, wide spacing might work best for you. And what do you want from each crop? If you need only big storage onions, plant them 4 inches apart. Baby onions for pickling or coq au vin? 2 inches. Both? Sow at 2 inches, then remove some at baby size to give the others room. For head lettuce you’ll need a spacing appropriate to the variety; for cut-and-come-again baby lettuce a thick-sown row. For both, you could sow a thick row, then thin at 3 inches tall, then let the rest mature. Broccoli spaced widely gives big heads all at once (good for freezing); broccoli spaced closely yields smaller heads followed by many side shoots. Cooks with small families can plant cabbages closely for smaller heads. Closely spaced leeks are more numerous but thinner. Tight spacing of celery yields heads that are more blanched but with thinner stalks. And there’s always the interplanting trick — set out lettuce, spinach or some other small, shade-tolerant crop in the wide spaces between corn, Brussels sprouts or pumpkins, then harvest them before they start to compete with the bigger crop. When is that? Experience will tell you.

“I wish plants could tell me how they want to be planted,” my friend complains. Often they do. If only the last plant in the row is up to size, the rest are too close together. That’s garden math I can believe in.

Barbara Damrosch’s latest book is “The Four Season Farm Gardener’s Cookbook.”

Barbara Damrosch

Barbara Damrosch

Barbara Damrosch’s latest book is “The Four Season Gardener’s Cookbook.”

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