Broccoli

Broccoli has a reputation for being demanding, and that reputation is earned. The plant is chasing a narrow band of cool temperatures — roughly 60 to 70 degrees Fahrenheit — and it will either stall or bolt if it spends too long outside that range. The central head develops under cool conditions and then opens into yellow flowers in a matter of days once the weather warms. Miss that window by a week, and the harvest is gone.

Start seeds indoors about six weeks before your last frost, and move transplants out right around the frost date. The seedlings can handle a light freeze, and getting them in the ground early gives you the best chance of maturing a head before summer heat arrives. For a fall crop — which many gardeners find more reliable — count back from your first expected fall frost and transplant accordingly, targeting harvest in the cooler weeks of September and October.

Broccoli is a heavy feeder. Work a generous amount of compost into the bed before planting, and consider a side-dressing of a balanced organic fertilizer three or four weeks after transplanting. The plants should grow steadily; if they stall and the older leaves start to yellow, they're likely running low on nitrogen. Consistent moisture matters too — the heads form under the outer leaves, and uneven watering can cause loose, open heads.

Cabbage worms are the most reliable threat. The white cabbage butterfly lays pale yellow eggs on the undersides of leaves, and the hatched larvae — small, velvety green caterpillars — chew through leaves and work their way into the developing head. Row cover installed at transplanting is the most effective prevention. If you forgo the cover, check leaf undersides every few days. Bt (Bacillus thuringiensis) is effective against young larvae and is safe to apply near harvest.

Watch the head closely in the final two weeks. Broccoli is ready when the head is tight and dark green, before any of the small buds show yellow. Once you see yellow, cut immediately — the flavor deteriorates and the central head is moving toward flowering. After the main head is cut, many varieties will produce smaller side shoots for several more weeks. De Cicco, in particular, is grown specifically for those side shoots rather than one large central head.