This unusual brassica isn’t widely available in supermarkets, so is well worth growing yourself. The swollen stem base, often called a bulb, can be green-, white- or purple-skinned, with pale green or white flesh inside. Kohl rabi is best harvested young, when tender, crisp and juicy, ideal for eating raw, grated into salads and coleslaws. It can also be lightly steamed, roasted or sautéed. It has a sweet flavour, like broccoli or mild turnip, to which it’s closely related. The leaves can also be cooked like greens.
Kohl rabi grows best in cool, damp weather. Always keep plants well watered, especially in hot, dry spells, to stop them turning woody or bolting. Unlike many brassicas, kohl rabi is fast growing, especially early in the year, so is ideal for filling gaps on the veg plot – you can harvest as baby veg in as little as six weeks and at full size in around 12.
Month by Month
There are several varieties of kohl rabi to choose from, with green, white or purple skins. Purple varieties make a particularly attractive addition to the veg plot. They also tend to be hardier and slower to mature, ideal for later sowings and harvesting into autumn or even winter. All kohl rabi are white or pale green inside.
F1 hybrid varieties tend to produce more vigorous plants and a reliable, consistent crop. It’s also worth choosing bolt-resistant varieties. For varieties that performed particularly well in RHS growing trials, see our recommended AGM fruit and veg.
You can also see many crops, including kohl rabi and other brassicas, in the veg plots at all the RHS gardens, so do visit to explore how they’re grown, compare the varieties and pick up useful tips and inspiration.
Kohl rabi seeds are available in garden centres and from online seed suppliers.
Preparing the Ground
Kohl rabi grows best a sunny spot with fertile, free-draining but moisture-retentive soil. Some varieties will also grow in partial shade, especially in summer. It dislikes acidic soil, so apply lime to raise the pH if necessary.
Weed the sowing site thoroughly, then add lots of garden compost – about two buckets per square metre/yard. Firm the soil, then rake to remove lumps and stones.
In cooler areas and heavy clay soil (which is slow to warm up), early sowings are best made indoors in modular trays.
About a month after germinating, when plants are no more than 5cm (2in) tall, prepare them for life outdoors and harden off for a couple of weeks – do this gradually, as a sudden drop in temperature can cause plants to bolt (flower). Plant outside once the soil has warmed up, spacing them 15cm (6in) apart, with rows 30cm (1ft) apart. It can also be beneficial to pre-warm the soil before planting out.
You can sow kohl rabi seeds from late February to early March under cloche or fleece, then in open ground from March to July, or to mid-August in warmer locations. Choose hardier purple varieties for mid- to late summer sowing.
Prepare the ground as detailed above, then make a drill 1cm (½in) deep. Water along the base, then sow seeds thinly, cover with soil and firm gently. Space rows 30cm (1ft) apart.
Thin out the seedlings when they are 2.5cm (1in) tall or have their first true leaves, to a final spacing of 15cm (6in) apart.
Sow little and often, every few weeks, for ongoing harvests through summer and into autumn. See our guide to successional sowing and our guide to growing baby veg.
Kohl rabi is easy to look after, just water generously and protect from pests.
Water kohl rabi seedlings and young plants regularly, so they never dry out.
Continue watering consistently and generously, especially in dry spells. Lack of water will slow their growth and cause them to turn woody.
Spread a thick layer of mulch, such as garden compost, around the crop to help hold moisture in the ground and suppress weed growth.
Keep the soil weed free, so seedlings and young plants don’t have to compete for light, water and nutrients. Hand-weed close to the plants rather than hoeing, to avoid damaging the swollen stems.
See our tips on controlling weeds.
Harvest kohl rabi when young, between golf-ball and tennis-ball size, to enjoy them at their sweetest, with a mild flavour and succulent, crunchy texture. If you leave them to get too big, they lose their flavour and tenderness. Particularly in hot, dry weather, they can easily turn woody.
With repeated sowings, kohl rabi can be harvested from May through to November. Protect with cloches if you haven’t finished harvesting before wintery weather arrives.
To prepare kohl rabi, it’s usually best to remove the outer skin, then grate or chop finely to use in salads and coleslaw. Kohl rabi can also be lightly steamed, sautéed or added to stews. The young leaves can be cooked like kale.
Use kohl rabi as fresh as possible, when succulent and full of flavour and nutrients. It can also be kept in the fridge for a few days. In autumn, some varieties can be stored in a cool but frost-free place for up to several months.
Protect seedlings and young plants from slugs and snails.
In hot, dry conditions, kohl rabi can turn woody or bolt (flower prematurely), so water generously and regularly. Early and late crops are usually more successful, avoiding summer heat. Harvest when young and tender, especially if conditions turn dry. Cold temperatures can also cause bolting, so don’t sow too early outdoors, and harden off indoor-sown plants carefully.
Being a brassica, kohl rabi is potentially susceptible to the usual brassica pests and diseases, but as it’s quite fast growing, it’s generally less affected than many of its slower relatives. Cabbage caterpillars are the most likely problem, so either cover plants with insect-proof mesh or fleece, or check the leaves regularly for caterpillars and eggs.
Applying lime helps to combat clubroot disease, as does starting plants off in pots until they have a strong root system.
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