How to grow sea kale

How to grow sea kale

All you need to know about growing sea kale, in this detailed Grow Guide.

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Sow
Sow

Do not Sow in January

Do not Sow in February

Do Sow in March

Do Sow in April

Do Sow in May

Do not Sow in June

Do not Sow in July

Do not Sow in August

Do Sow in September

Do Sow in October

Do Sow in November

Do not Sow in December

Plant
Plant

Do not Plant in January

Do not Plant in February

Do Plant in March

Do Plant in April

Do Plant in May

Do not Plant in June

Do not Plant in July

Do not Plant in August

Do Plant in September

Do Plant in October

Do Plant in November

Do not Plant in December

Flowers
Flowers

Plant does not flower in January

Plant does not flower in February

Plant does not flower in March

Plant does not flower in April

Plant does flower in May

Plant does flower in June

Plant does flower in July

Plant does not flower in August

Plant does not flower in September

Plant does not flower in October

Plant does not flower in November

Plant does not flower in December

Divide
Divide

Do not Divide in January

Do not Divide in February

Do Divide in March

Do not Divide in April

Do not Divide in May

Do not Divide in June

Do not Divide in July

Do not Divide in August

Do not Divide in September

Do not Divide in October

Do not Divide in November

Do not Divide in December

Take cuttings
Take cuttings

Do Take cuttings in January

Do not Take cuttings in February

Do not Take cuttings in March

Do not Take cuttings in April

Do not Take cuttings in May

Do not Take cuttings in June

Do not Take cuttings in July

Do not Take cuttings in August

Do not Take cuttings in September

Do not Take cuttings in October

Do not Take cuttings in November

Do Take cuttings in December

Harvest
Harvest

Do not Harvest in January

Do not Harvest in February

Do not Harvest in March

Do Harvest in April

Do Harvest in May

Do not Harvest in June

Do not Harvest in July

Do not Harvest in August

Do not Harvest in September

Do not Harvest in October

Do not Harvest in November

Do not Harvest in December

Sea kale, Crambe maritima, is a striking plant that is both ornamental and edible. The large leaves are a lovely glaucous green, with wavy edges, and in summer these are crowned with a cloud of tiny white perfumed flowers. These nectar-rich flowers are great for attracting pollinating insects. As the name suggests, sea kale is often found growing wild on the coast. In gardens, it looks good planted in dry sunny beds or into gravel, with other plants that favour this habitat, such as knifphofia and thrift. Or you could include it in your vegetable plot and harvest the young shoots in spring to eat raw or steamed – they taste like asparagus.

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Where to plant sea kale

For best results, grow sea kale in full sun or partial shade in fertile, very well-drained soil. The position needs to be deep enough to accommodate the long tap root of the plant with plenty of space for it to spread out. Sea kale is not suitable for growing in containers.


How to plant sea kale

How to grow sea kale - planting sea kale in a pot
How to grow sea kale – planting sea kale in a pot

You can grow sea kale from seed. The round bullet-like seeds have a hard, outer casing, so soak seeds and score to remove this before planting the seed in compost with a little bit of heat. Alternatively, young plants can be grown from root cuttings. Plant out young sea kale plants in early spring, into a well-prepared bed that is the final position for these perennial plants as they don’t like being moved.

In this clip from Gardeners’ World, Monty Don plants flowering sea kale alongside his pond:


Propagating sea kale

How to grow sea kale - taking sea kale cuttings
How to grow sea kale – taking sea kale cuttings

You can collect seed from sea kale plants at the end of the summer or take root cuttings – also known as ‘thongs’ – from older plants. These might be established sea kale plants coming to the end of their life so they can be dug up. Take cuttings from the side roots. Plant these ‘thongs’ into compost in early spring, covering with a layer of compost 2cm deep and grow on.


Sea kale: problem solving

Sea kale is a member of the brassica family and therefore can succumb to club root. They may also be attacked by flea beetles, while slugs and caterpillars love the tender young leaves, so use netting or other barrier methods to protect them.


Looking after sea kale plants

How to grow sea kale - forcing sea kale
How to grow sea kale – forcing sea kale

Seakale is a perennial and should be cut back in autumn. In spring add a thick mulch of well-rotted manure or garden compost. If you want to grow seakale as an edible, force the plants over winter, covering with a bucket or rhubarb forcer to get flavoursome young shoots that can be eaten raw or steamed. However, don’t try this until the second year, as it will weaken the plant.


Sea kale varieties to grow

Crambe maritima grows to 75cm and is a perennial with large glaucous green leaves and small, scented white flowers.

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Crambe cordifolia has been given the Royal Horticultural Society’s prestigious Award of Garden Merit (AGM). Larger than its maritime cousin, it grows to 1.8m and the foliage is dark green. The frothy sprays of small, scented white flowers are followed by seed pods. It looks good in a sunny border whether you are using it for the foliage or flowers. Beware, as the leaves have a good aroma of cabbage, but are not edible.