Planting kale: when, where & how to grow kale

Considered a superfood, kale is not only highly nutritious but flavoursome as well. Learn all there is to know about growing kale at home.

A member of the Brassica family of vegetables, kale (Brassica oleracea Acephala Group) has become more popular due to its high nutritional content. Well-suited to our climate it is hardy down to -15 ℃ and is a key winter crop. We will show you all there is to know about planting and growing kale and some other tips on caring for it.

As a member of the Brassica family, kale (Brassica oleracea Acephala Group) has become more popular due to its high nutritional content. Well-suited to our climate, as it is hardy down to -15 °C, making it a key winter crop. Read on to find out everything about planting and growing kale and some other tips on caring for it.

Planting kale: when, where and how

You can grow kale from seed in spring or from young plants in early summer, both of which you can buy online or from a garden centre. All kale varieties need a sunny site to thrive and produce their delicious and ornate foliage. However, kale will also tolerate some light shade.

When to sow kale

You can sow kale directly in the bed from March until June or undercover in spring to give it a head start. Being rated H5 for hardiness, kale is tough and does not need heat to germinate as long as the soil temperature is above 7 °C. However, your kale seeds will germinate more quickly around 10 to 15 °C. To sow kale seeds indoors, sow them individually in a module tray or pot prefilled with a seed-sowing compost at a depth of 1cm. Our Plantura Organic Herb & Seedling Compost is light in structure and low in nutrients, so it supports seed germination and gives kale seedlings a good start. With the soil kept moist but not wet, the kale seeds should germinate in around 5 to 7 days.

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Once the kale seedlings have developed their first pair of true leaves, you can pot them on individually using a multi-purpose compost. Grow on undercover for around 6 to 8 weeks, keeping the soil moist until they have developed a good root system. Once they are robust enough you can plant them outside in early summer after gradually hardening them off.

Where to grow kale

Kale thrives in a sunny or partially shaded spot. It can tolerate most soils but prefers a rich and fertile ground that is free-draining. Areas that are prone to water-logging or acidic soils should be avoided as the kale will struggle to thrive. In addition to this, kale should not be planted where other brassicas have grown in the previous 3 years, as this can potentially lead to issues with soil-borne diseases, such as club root (Plasmodiophora brassicae). Instead, practise crop rotation, which will not only help prevent a build-up of diseases in the soil but improve the structure and fertility of the soil as well.

Tip: before planting kale, check the pH of the soil using a soil pH meter and add lime to increase the alkalinity if required.

Planting kale

To prepare the ground for planting kale, lightly dig it over, remove any weeds and add some well-rotted manure or garden compost to increase the soil’s fertility. In early summer, plant out your young kale plants, spaced 40 to 60cm apart. Dig a hole twice the depth and width of the root ball and place the plant slightly more deeply than previously, so that the lowest leaves are just above the soil level. Backfill with soil, gently firming in as you go. You can also make little mounds of soil around the plants, which will help secure the top-heavy plants as they grow. Water thoroughly and add a layer of mulch to help conserve moisture and prevent any weeds from appearing. Continue to water throughout the growing season, making sure that the soil does not completely dry out.

You can also grow brassicas in a raised bed and if space is at a premium even grow kale in a container or pot. Growing kale in a raised bed has the advantage of working at a more convenient height. However, depending on the height of the raised bed or container you may want to grow shorter kale cultivars such as ‘Candy Floss’.

Tip: pests including birds and the cabbage white butterfly (Pieris rapae) can quickly strip kale plants of their leaves . To protect your kale crop, cover your plants with a brassica cage or fine netting.

Summary: sowing and planting kale

• Sow kale seeds directly into prepared soil or undercover from March until June
• When grown undercover, prick out the kale seedlings once the first pair of true leaves develop and pot on using a multi-purpose compost
• Keep the soil moist and gradually harden the plants off before planting out in early summer
• Plant out 6 to 8 weeks after sowing, 40 to 60 cm apart and slightly deeper than previously planted, firming in the soil as you go
• Keep the soil moist and cover plants with netting to protect the kale from pests

Watering, fertilising and propagating

Watering kale regularly is required after planting and whilst the plants are still young. However, once established, kale plants generally only need to be irrigated during dry or hot spells. If you grow kale in a pot, more frequent watering will be necessary to prevent the soil from completely drying out. When grown in fertile soil, you do not strictly need to add fertiliser at the time of planting. However, a high-nitrogen feed applied in spring will give the plants a boost, especially when growing on poor soil that is low in nutrients. Our Plantura All Purpose Plant Food can be used for fertilising kale, and as it is long lasting and high in nitrogen, it will encourage lush leafy growth for up to 3 months.

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Kale is usually grown from seed that is either bought or collected from plants that have gone to seed. You can harvest kale seeds by allowing the plants to overwinter and produce yellow flowers the following summer. Once the flowers have formed seed pods that have turned from green to brown, remove the seed pods and collect the seeds to store until required. If you plan on collecting kale seeds, other brassicas should not be grown near the kale as they can interbreed, which may lead to untrue offspring.

Although less commonly practised, you can also grow kale from cuttings. To grow kale from a cutting, remove a strong side stem with several small leaves and place it in a free-draining cuttings compost to root before growing on.

How tall does kale grow? If you are wondering how tall kale grows, the answer depends on the variety. For example, dwarf kales tend to grow no more than 30 to 40cm high, whereas taller varieties such as ‘Nero di Toscana’ can grow to more than 1.2m high.

Companion plants for kale

Companion planting is the technique of growing certain plants together for their mutual benefit. As with all vegetables, there are both good kale companion plants and those that should not be grown together. Here are just some of the good companion plants for kale:

• Calendula (Calendula officinalis)
• Chives (Allium schoenoprasum)
• Dill (Anethum graveolens)
• Garlic (Allium sativum)
• Leeks (Allium porrum)
• Nasturtium (Tropaeolum majus)
• Onions (Allium cepa)
• Sage (Salvia officinalis)
• Spring onions (Allium cepa)

However, not all plants should be grown with kale. It is not advisable to grow kale near or with other brassicas as this can encourage pests or other hungry crops that will compete for the nutrients in the soil, such as:

• Broccoli (Brassica oleracea Italica Group)
• Cabbage (Brassica oleracea Capitata Group)
• Cauliflower (Brassica oleracea Botrytis Group)
• Tomatoes (Solanum tuberosum)

Around September, you can start harvesting your kale to help see it through the winter. Learn how to harvest and store kale in our other article.