Brassicas such as broccoli and brussels sprouts do best when started in a protected spot and then transplanted to the garden.
Broccoli can be started in early March and then transplanted in mid-April for delightful clusters of green sprouts by early July. Transplant into good, highly fertile soil, and set them about 18 inches apart in the row. Harvest the main head when it reaches a full size but before it turns yellow--it takes some experience to recognize this stage at first sight. Side shoots will appear for many weeks as long as you harvest them at least every two days. Once you stop harvesting, the plant will erupt in pale yellow flowers and your days of broccoli will be over. To keep the yummy flowing, start up another round in May and a third round in late June. This last sowing will produce a fall crop, the tenderness and sweetness of which is unbeatable. Broccoli is not as good a candidate for overwintering situations; if you have a bounty, harvest and freeze before mid-November or so.
Brussels Sprouts are the brassica equivalents of leeks, standing tall and quiet and regal the whole summer long. Start seedlings in May--no earlier. Too-early crops reach maturity before the hard frosts arrive that make them so delicious, and it sometimes proves difficult to pull mature plants along an extra month until frost season. Transplant into fertile soil spaced about 24 inches apart. Keep weeded and avoid spots near the garden perimeter; weed competition will stunt plant growth (which is key to big, delicious yields) and slugs like to munch on the crop. To direct the plant's energy to the little clusters of sprouts, prune the growing tip off the top of the crop in mid-September. In our experience, Catskill sprouts tend to be looser than the hybrid sprouts, but their flavor is superior. Nothing beats a pan of quickly-sauteed garlicky sprouts on a cold November evening. Put them with some baked butternut squash, roasted potatoes, and a bowl of baked beans--pure heaven.
(Date suggestions reflect our early- to mid-May last frost date here in the Hudson Valley)