Saturday, 31 October 2015

Kale (Brassica oleracea)

Kale (Brassica oleracea) is an annual/biennial plant from the Brassicaceae (previously known as Cruciferae) family. Kale is also known as borecole, boerenkool, colewort and collard. It is a cold weather plant and commonly used as winter greens, particularly in the Northern Hemisphere. The Brassica oleracea species has been cultivated for at least 2000 years and a variety of forms have developed over that time.

An image of Kale (Brassica oleracea) growing in a polytunnel
Kale (B. oleracea)

There are eight main groups of brassicas and kale is considered part of the Acephala group. Acephala means 'no head' and the kale plant just produces leaves rather than a solid head like a cabbage or cauliflower.

How to grow kale

Sow seeds from March until June. Sow around 10cm deep in a permanent position in the ground and leave around 45cm between plants. Alternatively sow the seeds individually in pots. When plants have five or six true leaves transplant out into larger pots, where they can be grown to maturity, or in the ground. The exception is rape kale which doesn't like being transplanted so should be grown from seed in its final position.

Kale will grow in most soils but prefers a free draining loamy soil with a pH of 5.5 to 6.8. Kale likes moist conditions so water well throughout the growing season and mulch around the base to prevent loss of moisture. Feed the topsoil around the plant with homemade compost every 6-8 weeks to keep the leaves coming. Alternatively use other proprietary plant feeds. If we run out of compost, we use a liquid seaweed feed once in a while to top up nutrients.

Once the plant is large enough, leaves can be picked. Don't cut the whole plant down but use it as a cut-and-come-again plant. It will continue growing and producing new leaves. During this way it is possible to produce leaves throughout the year. Very hot weather may turn the kale bitter and tough but it is still edible. Leaves picked after a frost or very young leaves will taste sweeter.

Very few pests or diseases affect kale. Keep an eye out for birds and slugs. Plants grown outside can be netted to keep birds off. Slugs can be picked off by hand and re-located to a safe place. Gardeners may not like slugs but they are still an important part of the ecosystem and should not be destroyed. Large plants may need staking to ensure they remain upright. Always try and remove any yellow leaves growing underneath the plant to avoid disease.

The different types to choose from include curly kale, plain leaved kale, rape kale, leaf and spear as well as Cavolo nero. Within these different leaf types there can be found different named varieties.

Other uses

Kale is also grown as an ornamental or flowering plant. Kale leaves can be used as a dye.

Raw edible parts

The unopened flowers, the sprouted seed and the leaves of the kale plant are all edible raw. Use the unopened flowers in a similar way to broccoli. Kale can be grown indoors for sprouts or micro greens all year round. The health benefits of kale and the many raw food recipes have been well documented. Kale crisps and kale green smoothies are particularly popular

The ornamental or flowering kale is edible in the same way but may not have a good flavour. Sea kale (Crambe maritime), a perennial plant also from the Brassicaceae family, can also be used in a similar way.

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