How to Grow Kale

You can grow kale in many soil types and conditions, being a straightforward vegetable seeds to grow. However, they do prefer rich, firm, and well-drained soil. Generally, kale prefers full sun, although it can also be grown in partial shade.

To prepare the ground before sowing and planting, first remove all weeds within the area and then enrich the soil with well-rotted manure or garden compost. Afterwards, rake the soil until it’s level, then firm it well.

When to Sow Kale Seeds

Kale seeds are sown at different times depending on how you intend to grow them. If you’re starting your kale seeds indoors before later planting out, they should be sown around the middle of March. If you’re sowing seeds directly outdoors, they should be sown between March and June. 

How to Grow Kale from Seeds

Sowing Kale Seeds Indoors

Sowing kale indoors presents several benefits. Firstly, you don’t have to worry about slugs and snails attacking your seedlings, and the risk of clubroot disease is reduced as your plants will develop healthy roots before being planted outdoors.

If sowing kale seeds indoors, use modular seed trays to sow your seeds, as this prevents their roots from being disturbed when they are later transplanted outdoors. Fill each module with multi-purpose garden compost, water it well, then make a 1cm (½in) deep hole in each one. Sow two seeds in each hole, then cover the hole back up again. Thin the seedlings out as they begin to develop, then provide them with plenty of light and water them regularly.

Sowing Kale Seeds Outdoors

Kale seeds can also be sown outdoors. You can sow these seeds either directly in their final position to avoid transplanting, or in a seed bed. Sowing your seeds in a seed bed allows you to make space for other crops during the prime growing season while your kale seeds are seedlings.

If you’re sowing them in their final position, you should sow three seeds about every 45cm (18in) along a 1cm (½in) drill with rows at the same distance apart. However, your chosen variety may have more specific spacing requirements, so be sure to check the seeds' packet before sowing. When your seedlings begin to develop, thin them out to leave just one at each point.

If sowing them in seedbeds first, sow your seeds thinly along a 1cm (½in) drill, 10-15cm (4-6in) apart. Alternatively, you can thin them out to that spacing if you sow them more densely. After around six to eight weeks, your seedlings should be ready to transplant into their final positions.

How to Grow Kale in Pots

If you don’t have the space to grow kale in your garden, it’s also ideal for growing in pots. This should be done with multi-purpose compost in a large plant pot or container. You should grow compact varieties in pots, such as Kale Dwarf Green Curled.

Sow three seeds every 30cm (12in), then thin out to the strongest seedlings once developed. When growing kale plants in pots, space them out with 30cm (12in) between each plant. Ensure your pot plants are well-watered, especially in summer, as they are more prone to drying out than ground-grown plants.

When to Plant Kale Plants

Whether growing kale from kale plants or transplanting developed seeds to their final site, you should plant your kale plants between April and August.

How to Plant and Grow Kale Plants

You should transfer your plants to their final site once they have reached 10–15cm (4–6in) tall. If they have been grown indoors first, you will need to harden your plants off beforehand to acclimatise them to outdoor conditions.

When moving your plant, be careful not to disturb the roots, as this can impair their growth. When planting, plant them in holes deep enough so that their lowest leaves are at the soil’s surface. This will allow their roots to grow deeply, absorbing more water and nutrients. When planting, be sure to firm your kale plants in well, as they will become top-heavy and need to be secure. Then, ensure they are well-watered.

Give your kale plants plenty of space, allowing each plant about 30-60cm (12-24in) between them. This will enable them to each have plenty of light and air for successful growth and to deter diseases.

Watering

It’s essential that kale seedlings and young plants are watered frequently enough to prevent the soil from becoming dry, promoting healthy growth. However, take care not to waterlog the soil, as this can lead to the development of diseases and rotting.

Once your plants have matured, they will only need watering in dry spells. However, container-grown kale will require more frequent watering, as containers tend to dry out more quickly.

Feeding

You can feed your kale plants with a nitrogen-rich fertiliser, such as our Sulphate of Ammonia Nitrogen Fertiliser. However, this is typically only necessary when growing in particularly poor soil or in containers.

Mulching

Mulching is recommended for kale plants, as it helps prevent the growth of weeds and reduces the need for watering. You should add a thick layer of natural mulch, such as well-rotted manure or garden compost.

Weeding

You should make an effort to keep your kale plants free of weeds, as this prevents competition and ensures your plants grow to their full potential. It also prevents the development of fungal diseases by allowing for better airflow.

Support

Taller kale plants may need support provided in the form of bamboo canes in autumn, as strong winds in the colder seasons can cause them to topple over and loosen their roots.

When to Harvest Kale

You can harvest your kale plants from September onwards, up until around March, when they reach a height of about 10-15cm (4-6in).

How to Harvest Kale

Kale can be harvested as a cut-and-come-again crop, meaning that it will produce new leaves again after they are picked. However, be sure to select from different plants, as repeatedly picking from the same plant can weaken it.

Start to remove young leaves from the top of the plant. You should always pick the leaves when they are young and tender for the best texture and flavour.

Side shoots will begin to form after the main crown is harvested, which will be ready for use from February to May. You should pick these shoots when they are young and are 4-6in (10-15cm) long.

Kale is a hardy plant, so it shouldn’t present too many problems when growing. However, some common issues could arise, so follow our tips below to either prevent or remedy these:

• Birds - Birds are known to attack kale plants, so using garden netting or fleece can protect against them.
• Pests - Various pests can attack kale, such as cabbage root fly, cabbage caterpillars, slugs, and snails. You can protect your plants from these pests using various methods, such as garden fleece, slug and snail control products and cabbage collars.
• Clubroot - Clubroot is a disease that causes plant roots to become severely distorted and swollen, resulting in poor nutrient and water absorption and poor growth. The best way to deal with clubroot is by using preventative measures, such as buying disease-resistant vegetable seeds, growing seeds from trusted providers and practising good garden hygiene. For more information on clubroot, our guide on how to prevent clubroot disease provides further advice.
• White blister - White blister is a fungal disease relatively similar to downy mildew, spotted by the blister-like white pustules it produces. It can stunt and distort the growth of your kale plants, though the best course of action is preventative, not reactive. You should practise crop rotation and ensure each kale plant has plenty of airflow to prevent white blister. Any affected plant material should be burned or binned, and severely affected plants should be removed entirely.

Now that you know all about how to grow kale from seed, you can get started by shopping our kale range at D.T. Brown. Across our extended selection of gardening products, you can find a wide range of cultivars in our kale seeds and kale plants collections, offering many colours and flavours to try out in your growing space. You can trust our high-quality products, as we have over a century of experience in providing UK gardeners seeds and plants that produce vigorously growing, delicious crops.

You can learn how to grow many other vegetable seeds and fruit seeds by browsing our many other detailed growing guides and blogs on our garden blog. You can also read our guide on how to grow brassicas for more general tips, where you can find many of our other brassica growing guides.

If you’d like to know anything more about our collection of fruit plants, herb plants, garden accessories, or anything else you can find in our shop, get in touch today, and a member of our team will get back to you as soon as possible.