Brett Grohsgal's Raising Winter Greens talk
Guest Blog by Diane Svenonius
September’s talk in the DC Urban Gardener series at the HSW featured Brett Grohsgal of Even’ Star Farms speaking on planting for a harvest of delicious greens all winter. Brett farms in St. Mary’s County, MD, and provides CSAs to 200 families, summer and winter. In winter, he grows 23 acres of greens and roots, and lettuces in a greenhouse.
The best plants to choose for winter crops are the brassicas -- arugula, mustard, turnips, radishes, collards, kale, tat soi (but not bok choi, which bolts in winter); some asteraceae -- lettuce, radicchio; and umbelliferae, such as parsley, chervil and cilantro; turnips, and radishes. Brett warned that lettuces will not yield a crop all winter due to leaf burn from frost, but kale and other brassicas are more flavorful after a freeze and thaw. The best lettuces for planting now are buttercrunch, red salad bowl, and rouge d’hiver.
In our area, planting should be completed by October 15 at the latest so that plants will be established before serious cold sets in. Winter crops must be planted from seed, and seeds of hybrids are less cold-tolerant. Transplanting breaks off the primary root tips; to make up for it, the plant will send out secondary roots that grow too shallow for winter survival.
In winter, the sun is lower than in summer, but with leafless trees, the gardener may get the necessary minimum three hours of sun for winter beds. Good drainage is critical, using raised beds if necessary (vermiculite is a good additive to soil), but pak choi, chervil, and field cress will tolerate some wetness. Water well after planting, then every three days until seedlings have six leaves. (If seedlings don’t appear, suspect slugs.) Mulch around the plants with autumn leaves or pine needles; microbes in the mulch give heat to the roots. Nitrogen can be added in the form of fish emulsion and coffee grounds. Established plants will do well under snow, which protects from severe cold and icing; an ice event with no snow is the most dangerous condition. Brett said that Channel 7 gives useful frost warnings for the area.
Brett recommends harvesting by selecting leaves from each plant for winter crops, starting with tiny leaves to use in salad and taking no more than a third each every ten days. If the whole plant is taken (shorn) when sunshine is lacking, the plant will not be able to produce enough leaves to survive. Brett said never to harvest when the plant is frozen.
Brett showed slides of his kale beds alternating with beds of a cover crop, which will be turned under to improve the soil for the next season’s planting. Home gardeners can mulch their unplanted beds with the leaves that are falling this month, and with coffee grounds for added nitrogen.
Brett went into even more detail on winter greens in his article published in Edible Chesapeake's Fall 2008 issue. To see Brett's article click here.
Diane Svenonius is newsletter editor for the Takoma Horticultual Club in Takoma Park, MD.