Whether you are an experienced gardener or one of the many new gardeners spurred by the economy to grow vegetables, you want to be sure to maximize your investment. That is best done by making full use of your garden space.
Many people harvest a crop, pull up the exhausted plants, then leave that space in the garden empty. With a little careful planning, you can instead harvest a second crop, and sometimes even a third from that formerly wasted space and prevent the erosion and loss of nutrients that often occurs when a patch lies fallow.
"One classical example of double cropping," says agronomist Ajit Nehra, manager of Phoenix Organics, "is planting garlic or onions in October. They will usually grow six to nine inches before the snow comes, then they stop growing and overwinter. In the spring they start growing again, and they are ready for harvest in July. Then you still have time to grow beans, squash or cucumbers in that space. You have to use the early maturing varieties of course."
With several ways to achieve a "double harvest," the terms are sometimes confused. All are known as types of succession planting. And the goal of all is to make more efficient use of the space and soil nutrients. To synthesize the information from our experts:
- Double cropping generally means replacing a harvested plant with another, often completely different, seedling.
- Intercropping means two different types of plants, which are harvested at different times, are planted so that part of their growth cycle overlaps.
- Relay cropping means a second crop of the same type of plant is planted after the first crop flowers.
The key to making this work is knowing the time it takes to grow the plant you've selected—from germination to harvest. Plants which will take months to harvest are usually the ones where you can intercrop faster growing plants like lettuces, radishes or scallions. By the time the major crop needs all the space and water, the faster crops will be gone.
"Plant things compatible, not competitive, with each other," suggests Marsha Waite, who coordinates the Jackson County Master Gardener Plant Clinic. "You don't want plants that compete for the same nutrients. That way you are using your soil to the best of its ability."
Planting beans or vining squash after corn, which allows the vines to use the corn stalks for support, is the classic "three sisters" combination. Planting seedlings is generally preferable to just reseeding.
To ensure that you don't give an advantage to plant diseases or insects, Waite says it is also important to keep track of planting locations, in order to rotate plantings. "If you had no problems with diseases or insects then you can replant (those same varieties) in that area after three years. Otherwise, wait four years," she says. The Garden Guide for the Rogue Valley, by the Master Gardener Association, gives rotation guidance.
With a little careful planning, you can have your garden producing almost year round.