Harvesting Brussels sprouts: why frost makes them sweeter
Brussels sprouts turn milder after the first cold nights. Here's how to spot the right moment and pick them properly.
October is when the Brussels sprout harvest begins, and it runs well into winter. If you know when and how to pick, you get tastier sprouts and more of them.
When Brussels sprouts are ready
Brussels sprouts reward patience: sown in spring, harvested from October well into January. A sprout is ready when it is about walnut-sized, firm and closed. The order is always the same: the lower sprouts on the stem ripen first, the upper ones follow weeks later. Loose, opened-up sprouts have usually been left too long or grown in warm weather, and they taste less fine.
A tip for data fans: write down the date of your first pick. Next year you’ll see at a glance whether your variety is early or late.
Why frost improves the flavor
Brussels sprouts tolerate frost well, usually down to about minus 10 °C. In the cold the plants convert starch into sugar, so the sprouts taste milder and sweeter. If you pick them at 15 °C, you often get the more bitter version.
So there’s no need to rush out of worry about the first frost. If anything, a few cold nights are a mark of quality. Only in a hard freeze should you wait: don’t pick while the sprouts are frozen solid, because they break easily and the stem and leaves can get damaged. Wait until they have thawed in the late morning.
Pick from the bottom up
Snap the sprouts off with a small sideways twist or cut them close to the stem with a sharp knife. Remove the yellow leaves below as you go. That gives the stem more air, and the leaves are fine for the compost.
Leave the green leaves at the top of the stem. They keep feeding the plant while the upper sprouts are still growing. If the plant is still growing tall in autumn, you can pinch out the top. It then puts its energy into the sprouts, and they ripen more evenly.
Keeping and freezing
Unwashed sprouts keep in the fridge for about a week. For larger amounts, blanch them in boiling water for three to four minutes, chill them in cold water, and freeze them.
Alternatively you can dig up the whole plant with its roots and hang it in a cool, frost-free place. The sprouts then stay fresh for a while longer.
After harvest: keep crop rotation in mind
Brussels sprouts belong to the cabbage family. To keep diseases such as clubroot from building up in the soil, avoid growing any brassica in the same spot for several years. A break of four years is a common rule of thumb. Soil that is not too acidic helps as well, because clubroot favors acidic soils.
A bed plan in which you note year by year what grew where makes crop rotation easy. You can do that in Rootivo too.