Here is a short list of vegetables for your cool-season garden!
Arugula, Beets, Bok choy, Broccoli, Brussels sprouts, Cabbage, Collards, Carrots, Cauliflower, Celery, Cilantro, Chard, Fennel, Kale, Kohlrabi, Lettuce, Mizuna, Mustard Greens, Onions, Peas, Potatoes, Radishes and Spinach.
Broccoli - may be ready for harvest from early to mid June. Cut the heads when they are blue-green in color. Cut the central stem several inches below the main head but leave the side shoots for harvest later. These side shoots will produce until hot weather arrives.
Brussels Sprouts - A light frost will improve the flavor of Brussels sprouts. The sprouts should be harvested from the bottom up as they become firm. The sprouts should be 1 to 1 1/2 inches in diameter and green. Please do not remove the lower leaves as these are needed for growth.
Cabbage - should be harvested when the heads are firm. They should feel solid and heavy before you cut them. Mature cabbage heads are prone to splitting if they are too mature or if they receive excessive water such as after a heavy rain or watering after a dry period.
Cauliflower - will be ready for harvest in mid to late June. Cut while the heads are still tight and about 5-6 inches across. If the flower buds begin to separate (or become ricey) it is past its peak. Cauliflower must be bleached or blanched to produce a pure white head. To do this pull a few of the larger leaves up and over the head when they are a few inches across and secure with twine or rubber bands.
Pests & Diseases - The most common problems affecting cole crops are cabbage worms and buttoning.
Cabbage worms are small green caterpillars that become more active as the weather warms. They can be manually removed but easily hide in dense foliage (such as cabbage leaves). A spray containing Baccillus thurengensis (a deadly bacteria to the worms but harmless to us) can be used. Floating row covers, a light-weight fabric material, can also be used to cover the plants and prevent the moths and butterflys from laying their eggs on the plants.
Buttoning occurs when broccoli and cauliflower plants are exposed to stressful growing conditions and produce heads prematurely. This can be prolonged periods of temperatures blow 50 degrees F., dry conditions and poor soil.
If it's St. Patrick's Day then it is time to think about planting potatoes. Mid-March to Early April is the ideal time to plant as long as your soil is not too wet. Potatoes like cool temperatures and plentiful moisture. These plants, whose ancestors came from South America's Andes mountains, prefer well-drained, loose soil. Heavy, wet soil simply will not do. Purchase your "certified" 'seed' potatoes from your local garden center and cut them into small pieces with at least two 'eyes.' Dig a hole about 3-4 inches deep, plant the seed potato and cover with soil. As the potato grows pull loose soil up around the stem. This is called 'mounding' or 'hilling' your potatoes. Mound your potatoes to about 12 inches. Your new potatoes will grow off of the stem just above your 'seed' potato.