Plant for Productivity
No matter which variety you grow, you must start the seeds early. As their name suggests, snowpeas are cool-loving crops—they can germinate when the air temperature is as low as 40 degrees F, though they sprout most reliably between 50 and 60 degrees F. The young plants endure light frosts just fine without protection.
Eliot Coleman, renowned expert on gardening in cool conditions, used to start snowpeas indoors and later transplanted the seedlings to his garden. But he has developed a different system that has him plucking pods in his Harborside, Maine garden earlier than ever before: He sows two rows of 'Short N' Sweet' snowpeas along the back wall of his cold frame (behind some salad greens) around March 15. By the time the vines grow tall enough to touch the lid, the season has advanced enough that Coleman can safely remove the cover and let his snowpeas grow unprotected.
Coleman says that some of his friends who live in climates with mild winters (zone 7 and south) get an even earlier start—they sow their snowpea seeds in late fall, and then just wait for them to sprout the following spring.
Call it cabin fever or call it the lure of the season's first crop; whatever the cause, lots of gardeners like to challenge the conventional wisdom on planting dates. "Experiment by starting some snowpeas earlier and some later," advises Coleman, "and prove the experts wrong about when you should plant them."
Whenever you sow your seeds, you'll get more pods if the plants have a little extra space between them, says Brian Kahn, Ph.D., a horticulture professor at Oklahoma State University in Stillwater. Dr. Kahn compared snowpea plants growing 4 inches apart in double rows to ones growing 2 inches apart in single rows and found that the plants grown 4 inches apart yielded as much as 23 percent more (excuse our metric) grams of pods than the 2 inchers! "We believe that plants spaced 4 inches apart branch more, and have more pods on those branches," explains Dr. Kahn, "while the vines planted 2 inches apart barely branch at all and get bearing nodes only on the main stem."
Another way to ensure high snowpea yields is to inoculate the seeds. The inoculant contains a bacteria (which occurs naturally in some soils) that stimulates the formation of nodes on the plant's roots that enable the plant to extract nitrogen from the air, allowing the plant to virtually feed itself—a phenomenon called "nitrogen fixing." You shake the seeds in a plastic bag containing the powdered inoculant (available from many seed catalogs and garden centers).