How Do You Know When Brassicas Are Ready to Harvest?

The brassica family — cabbage, broccoli, cauliflower, kale, Brussels sprouts, kohlrabi — is the backbone of the winter kitchen garden. Each member has its own harvest window and its own set of signals, and the penalty for missing the moment ranges from bolted broccoli to cracked cabbage. Understanding each crop individually is worth the time.

Broccoli: Before the Buds Open

Broccoli must be harvested before the tight green buds begin to open into yellow flowers. Once even a handful of buds separate and show yellow, the head has peaked. Cut the central head with a sharp knife, leaving 10 cm of stem attached. This stem is edible and often as flavourful as the head itself. Most varieties will then produce side shoots — smaller, looser heads — for weeks if you continue to cut them promptly. These secondary heads are often more tender than the original. Cutting in the morning when the buds are tight gives the best shelf life.

Cauliflower: Cover and Cut Promptly

Cauliflower heads — curds — should be harvested when compact and white (or purple or green, depending on variety) before they begin to separate into sections. Once the curd starts to open, flavour declines and the texture becomes grainy. To protect white cauliflowers from yellowing in strong sunlight, snap a few outer leaves over the head as it develops — this keeps the curd pale and flavourful. Cut with a generous portion of surrounding leaves, which protect it during transport and storage.

Cabbage: The Firm Head Test

Squeeze the head firmly with both hands. A ready cabbage is dense and hard, like a bowling ball. A loose cabbage still has growth to go. Once firm, harvest promptly — left too long in wet weather, outer leaves split and the head cracks, allowing disease in. Cut at the base, leaving a short stump in the ground; making a cross-cut in the stump often stimulates a cluster of small secondary heads that are worth eating.

Brussels Sprouts, Kale, and Kohlrabi

Brussels sprouts mature from the bottom of the stem upward. Harvest lower sprouts when they are firm, round, and 2–3 cm across, snapping them downward. Kale leaves are best harvested young and regularly — always leave the growing crown intact. Kohlrabi should be cut when the swollen stem is 5–8 cm across; beyond that the texture turns woody. A light frost improves the sweetness of both kale and Brussels sprouts, so do not be in a hurry to harvest the first picking of these at the first cool weather.