Many claims of benefits from companion planting (growing two crops together) are no more than wishful thinking. Tangible benefits, however, come from intercropping (also known as relay planting, interplanting or undersowing), which is when one crop (or cover crop) is sown or transplanted in the spaces between the standing crop before it is finished. Don’t worry about whether the two crops benefit each other, just look at how the gardener benefits! Growers who like to get maximum productivity from their land or the length of their growing season are drawn to intercropping. It is a way to maximize the diversity of insects and other beneficial organisms as well as increasing the productivity of the land. There may be other benefits such as sharing row cover, or irrigation.
Sometimes a small or quick-growing crop is planted between slower growing crops to use the space not yet needed by the slower crop. Sometimes a tall crop and a sprawling crop are planted together. Sometimes a later, slower, crop is given a chance to get started before the first crop is cleared. The first crop may act as a “nurse crop” in providing some shade, or some soil-holding roots. It is important that the intercrop not be allowed to outcompete the main crop, and that no weeds get any chance to compete with either crop. High soil fertility is needed to make this work.
Some intercropping gardening tips include planting spinach with peas, chard with lettuce or scallions, okra with cabbage, peanuts with lettuce. Using relay planting enables a cover crop to get established in a timely way that would not be possible if we waited for the food crop to be finished first.
Here I’ll write about relay plantings in the early spring vegetable garden. In the future I’ll cover late spring intercropping and late summer and fall undersowing of cover crops.
Interplanting peas in spinach beds saves time and space and makes good use of resources. Being a legume, peas do not need high levels of nitrogen in the soil, so interplanting in a standing crop without adding any more compost will work fine in soils with good fertility.
Because spring heats up quickly here in central Virginia, we have a short season for peas – we have to start as early as possible, or it’s too late to get any. We plant a single or double row of peas in the middle of each spinach bed and take care of the two crops together, with the spinach gradually giving way to the peas as spring advances. The crops share the rowcover, the warmer soil, the cultivations, the compost and, above all, the space. One tilling is eliminated and the bed is doubly productive. Having two crops together keeps our attention on the need for weeding and harvesting.
The trick is to plan ahead when planting spinach. We leave a slightly wider central space between the inner rows of spinach (less than a whole extra row’s worth, as peas are a vertical crop). We’ve found the Row Marker Rake from Johnny’s to be a very worthwhile investment for making consistently parallel rows, and making faster hoeing possible. In the fall we plant beds of spinach with four rows in a 4-foot (120 cm) bed. When winter arrives, we cover the beds with sturdy double hoops and thick rowcover, to save the spinach from getting weather-beaten and to help it grow fast. We also transplant more beds of spinach in early spring.
Here’s how to grow the peas: because the beds are already warm under the rowcover, we can sow earlier than in uncovered soil. We aim to sow ours on March 1st, or whenever the forsythia blooms. Snap pea seed is more vulnerable to rotting in cold soil than shelling peas, probably because the seed is higher in sugars as opposed to starches. Shelling peas can be sown earlier.
In preparation for planting peas, we soak the seed overnight and hoe and weed the spinach. Before we make the furrows for planting the peas, we harvest the bigger leaves from the inner rows of spinach. We make one or two shallow drills (furrows) down the bed middles, sow the peas and replace the row cover.
By the time we want to stake the peas, we’re also ready to uncover the spinach to slow down the bolting, and we need to use the rowcover elsewhere for newer crops. We do another round of weeding and install the pea stakes. We harvest spinach leaves throughout the spring, about once a week for each bed. As they prepare to bolt, we harvest whole plants. We clear the spinach in April and May and continue growing the peas. Eventually we are left with a bed of peas only. One year we discovered the built-in, fail-safe feature of this method: if you fall behind with string-weaving the peas and removing the bolting spinach, then the tall spinach flower stems will support the peas!
Interplanting chard with a fast-growing crop such as lettuce or scallions (green onions) is another possibility, as an alternative to mulching the chard. Transplant the chard at the usual in-row spacing, with about 16 inches (37 cm) between rows. Transplant lettuces or clumps of scallion plants between the chard rows. Keep these crops growing fast and harvest the scallions and lettuce after about five weeks, before the chard gets too big.
Pam Dawling is the garden manager at Twin Oaks Community in central Virginia. Her book, Sustainable Market Farming: Intensive Vegetable Production on a Few Acres is available at Sustainable Market Farming. Pam's blog is on her website and also on Facebook. Pam often presents workshops at MOTHER EARTH NEWS FAIRS, and also writes for Growing for Market magazine.
Photos by Kathryn Simmons (peas and spinach), Southern Exposure Seed Exchange.
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