Heat and lushness define the garden in July, so it’s hard to even think about one of the last of the season’s vegetables to mature, namely Brussels sprouts. But that tardiness also prompted a friend to ask, “Is it too late to start some?”

Theoretically, yes. Even with Washington’s long growing season, it’s best to start Brussels sprouts in late spring — but no sooner, because you don’t want them to mature while the days are still on the warm side. The flavor will not be nearly as good. An acquaintance who teaches young children to garden tells her pupils never to taste a Brussels sprout until after the first frost. What a great early lesson to learn about the pleasures of green vegetables, the mysteries of flavor and the fact that the cool months are sometimes the most bountiful and the most benign.

Summer heat may work its alchemy on fruiting crops like tomatoes and melons, giving fullness and complexity to their flavors, but for green fare it’s a chill that brings them to their prime and a light hand at the stove that does them justice. When cooking them, heat that is too high or prolonged can ruin the delicate sweetness of a Brussels sprout. In recent years, roasted ones have become a popular side dish on restaurant menus, and too often they’re too darkly seared or too mushy — or both.

This is a good moment to be thinking about other brassicas, with plenty of time yet to sow seeds of faster-maturing members of the family for a fall and winter harvest. The list includes broccoli, kale and kohlrabi.

In the end, I gave my friend’s plan a green light, knowing it contained an element of chance. Unlike a kale plant, from which you can steal some leaves for nibbling even when it’s young, a Brussels sprout plant must be mature to head up those little round treasures. Once they’ve been formed, they can sail through much of the winter unscathed. I once saw a variety called Red Rubine in an alpine garden in late January, the sprouts deep maroon and still tender.

My buddy thought he’d try local nurseries to see whether they had some Brussels sprout transplants for sale, but if he strikes out he might sow some directly (then later thin them to 18 inches apart). If he goes that route, it should be with an extra-early variety such as Franklin (from Territorial Seed Co.), Early Marvel Hybrid (from Burpee) or Churchill (from Johnny’s Selected Seeds). Next to Churchill in the catalogue I also spotted an intriguing new item called Flower Sprouts, a cross between Brussels sprouts and kale. Apparently these flowerlike things grow on tall stalks just like Brussels sprouts, with equal cold resistance, and “have a taste and texture similar to Red Russian kale.”

Worth a try. But my friend’s quest is for the taste of a Brussels sprout, and I wish him good fortune with it.

Damrosch’s latest book is “The Four Season Farm Gardener’s Cookbook.”

Tip of the week:

Examine summer squash, zucchini and cucumber vines regularly, and harvest fruit at the small to medium size to promote continued production. The fruit quality is reduced if vines are allowed to dry out. Give them a good soaking when their beds become dry. — Adrian Higgins