Kale is the most honest winter vegetable the garden has to offer. While most beds lie empty and brown in November, it stands there strong and green and can be harvested fresh through snow and frost. Hardly any vegetable is so winter-hardy and at the same time so rich in vitamins.
Many myths surround one detail: does kale really need frost to taste good? The short answer is that there is something true in it. This article explains what actually happens with the cold stimulus, and shows how to grow kale from planting to winter harvest.
Why frost makes it sweet
The core of the old gardener's wisdom holds. When it turns cold, the plant converts part of its stored starch into sugar. The sugar acts like an antifreeze and lowers the freezing point in the cells. As a pleasant side effect the leaf then tastes milder and sweeter, less bitter.
The subtlety matters: what is needed is not the one hard frost but sustained cold. Several cool weeks in late autumn are already enough. Modern varieties are bred milder anyway. So you do not have to wait for the first freezing day, but a few cold nights do the flavour good.
Growing: plant early, leave standing long
Kale is a long crop. It is sown from May, the young plants set out in June or July with plenty of space, because the plants grow large and heavy. A firm, nutrient-rich soil and a sunny spot are ideal. As with all cabbages, a thought-through crop rotation helps, so that no cabbage diseases build up in the soil.
Why kale is worth it
- Harvests all winter
A single plant stands from November into March and keeps supplying fresh leaves. No storage needed, you harvest when you cook.
- Grows on from below
Harvest the lower leaves and the plant grows on at the top. That way you crop the same stem for months.
- Green or red, tall or low
Besides the classic green there are decorative red varieties and low ones that fit a pot too. Red varieties are an eye-catcher as well.
- Robust and easy-care
Once established, kale needs little. Its greatest enemy is not the winter but the cabbage white in summer.
How you grow kale
Sow from May
Sow into a seedbed or pots. Kale germinates reliably and grows briskly into sturdy young plants.
Plant in June or July
Set into firm, nutrient-rich soil 50 centimetres apart. The plants grow large, give them space.
Protect from the cabbage white in summer
A fine net keeps off the butterflies, whose caterpillars otherwise strip the leaves bare. More on it in Protecting cabbages.
Harvest from November, from below
From the first cool weeks pick the lower leaves. The plant grows on at the top and keeps supplying into March.
Plant early, leave standing long, harvest from below. And a few cold nights make it sweet, all by themselves.
The core rule for kale
Frequently asked questions
Does kale really need frost to taste good?
At heart yes, but not the one hard frost. Cold makes the plant convert starch into sugar, which makes the leaves milder and sweeter. Several cool weeks in late autumn are already enough, and modern varieties are milder anyway.
When do you plant and when harvest kale?
It is sown from May, planted in June or July. It is harvested from November all through winter into March. Kale is a long crop that stands in the bed for months and keeps supplying more.
How do you harvest kale correctly?
From the bottom up and never the whole plant at once. Pick the lower, full-grown leaves and leave the middle standing. From it new leaves keep coming, so you crop the same plant for months.
Is kale winter-hardy?
Yes, kale is one of the most winter-hardy vegetables there is and survives frost and snow easily. You can harvest it fresh from the bed in sub-zero temperatures. Only with deeply frozen leaves better wait until they have thawed again.
Why do my kale leaves get holes in summer?
Those are usually the caterpillars of the cabbage white, the most important pest on kale. A fine protective net over the bed keeps the butterflies off and is the simplest protection. Egg clusters picked off the underside of the leaves help as well.
