Kohlrabi

Sun

Full sun; light afternoon shade can help in warm weather.

Water

Keep the soil evenly moist, supplying about 1 in (2.5 cm) of water weekly when rainfall is insufficient.

Soil

Fertile, moisture-retentive but well-drained soil, ideally pH 6.0-7.5.

Height

1-1.5 ft (0.3-0.45 m)

Spread

0.7-1 ft (0.2-0.3 m)

Foliage

Long-stalked, blue-green leaves emerge from a rounded, green or purple swollen stem above the soil.

Growth

Fast; many varieties reach harvest size about 6-10 weeks after sowing, depending on conditions.

Care needed

Medium

• Edible

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   0.5 ft (0.15 m)

2. After 1 year

   1.2 ft (0.38 m)

   full size

Full size in one season.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the UK

Growth rate

Fast

• Thin or transplant seedlings to 6-9 in (15-23 cm) apart, allowing more room for large varieties.
• Water regularly; do not let the soil repeatedly dry out and then become saturated.
• Mix compost into the bed before planting; use a balanced vegetable fertiliser on poor soil according to its label.
• Mulch lightly once seedlings are established, keeping mulch clear of the swollen stems.
• Cover young plants with insect mesh, securing the edges against cabbage root flies and butterflies.
• Rotate with non-brassica crops, ideally leaving at least three years between brassica crops in the same bed.

Pruning. No routine pruning is needed. Remove damaged or diseased leaves, but retain most healthy foliage until harvest.

For most varieties, cut the stem just below the swelling when it is about 2-3 in (5-8 cm) across, firm and still tender; varieties bred for large size can be harvested later according to their seed instructions. Pick a few young leaves for cooking without stripping the plant, or use the healthy leaves when harvesting the whole stem.

Late winter

In mild climates, sow under cover for an early crop; avoid starting so early that young plants face prolonged cold.

Spring

Sow outdoors when soil is workable and warming, or plant hardened-off seedlings without burying their stems deeply.

Late spring

Thin seedlings, install insect mesh and sow another small batch for a staggered harvest.

Summer

Harvest promptly and maintain even moisture; pause sowing during sustained heat.

Late summer

Sow an autumn crop, allowing enough growing time before regular hard frosts.

Autumn

Harvest remaining stems before severe frost and clear crop debris; mild-winter regions can continue growing through winter.

• Plant in short, repeated rows in a potager for a clear pattern of rounded stems and upright leaves.
• Alternate green and purple forms along raised-bed edges for contrasting colour.
• Grow among lettuces and spring onions in mixed edible beds, leaving room for the kohlrabi to mature.
• Use in deep containers near the kitchen for an accessible, short-season crop.

Garden styles it suits: Potager (kitchen garden), Edible landscape, Cottage garden, Homestead, Small-space and Family-friendly.

Plant it with: Lettuce, Spring onions, Beetroot, Spinach, Dill and Calendula.

Wildlife: Leaves feed cabbage white butterfly caterpillars and other brassica-feeding insects. Plants left to flower provide nectar and pollen, but flowering usually means the edible stem is past its best.

• Cabbage caterpillars chew leaves: use fine insect mesh from planting and inspect leaf undersides regularly, removing caterpillars by hand.
• Cabbage root fly larvae damage roots, causing wilting or poor growth: protect seedlings with well-sealed insect mesh and remove affected plants.
• Clubroot causes swollen roots and stunted growth: remove infected plants, avoid moving contaminated soil and keep brassicas out of affected beds; test soil before adjusting pH.
• Woody, tough or split stems result from delayed harvest, heat or uneven watering: grow in cool weather, water consistently and harvest at the recommended size.

The swollen stem and leaves are edible for people and are not generally regarded as poisonous to cats or dogs in small food amounts, although they may cause gas or digestive upset. Do not offer large quantities to horses: brassicas can cause digestive and other health problems when eaten in bulk.

• Turnip (Brassica rapa subsp. rapa)

  The swollen part is mainly a root at soil level, with leaves clustered at its crown; kohlrabi has a swollen above-ground stem with leaf stalks attached around its sides.

• Swede or rutabaga (Brassica napus Napobrassica Group)

  Forms a swollen root partly buried in soil, usually with yellowish flesh and leaves arising from the top rather than around an exposed round stem.

• Celeriac (Apium graveolens var. rapaceum)

  Has divided, celery-scented leaves and a rough, knobbly base with many roots, unlike kohlrabi's smooth swelling and broad cabbage-like leaves.

Kohlrabi comes from German words for cabbage and turnip, referring to its cabbage ancestry and turnip-like shape.

Propagation. Raise from seed sown about 0.5 in (1 cm) deep, directly outdoors or in modules for transplanting while young. Make small sowings every two to three weeks during suitable cool weather.

Accepted botanical name

Brassica oleracea Brassica oleracea var. gongylodes is an older name for Brassica oleracea.

In the US and Canada

Introduced in the lower 48 states, Pacific Basin and Puerto Rico.

Native range

France, Great Britain and Spain.

Measured

Soil pH 7 to 7.5. Average height 50 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.