Kohlrabi (German turnip) care

Light

Kohlrabi needs sun on the leaves, not just bright ambient room light. Full sun, at least 6 hours daily, for fast, even swelling of the stem. It tolerates light shade but bulbs up more slowly; weak light gives small, leafy plants with poor 'bulbs'. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Outdoor kohlrabi crops want when the top 2-3 cm of soil is dry, about every 4-7 days. The single best habit is a finger-test before watering — push a finger 3-4 cm into the soil. Damp = wait a day; dust-dry = water deeply at the base of the plant. Needs steady, even moisture (~25 mm/week) for crisp, tender bulbs. Irregular watering, especially drought followed by rain, causes the swollen stems to split and turn woody and stringy.

Soil and pot

Kohlrabi grows best in fertile, free-draining loam, ph 6.0-7.5. Likes light-to-medium, moisture-retentive ground enriched with compost. Good drainage and steady fertility keep bulbs sweet and crisp; lime acidic soils to reduce clubroot risk. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Kohlrabi sits happiest at around Outdoor ambient humidity and 15-24°C (60-75°F). An outdoor crop with no special humidity needs. It prefers cool growing conditions; hot, dry weather slows swelling and pushes plants to bolt before the bulb develops. If you keep the room above 15 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed kohlrabi sparingly. Moderate feeder. Work a balanced general fertiliser into the bed before sowing. On poorer soils, a single nitrogen side-dressing as plants establish keeps growth steady; avoid excess nitrogen, which delays bulbing and grows leaves at the expense of the stem. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on kohlrabi in the Growli community. Each is annotated with the most common cause so you know where to start.

• Woody, split bulbs — Caused by drought, irregular watering or leaving bulbs too long. Keep moisture even and harvest young, ideally when the swollen stem is tennis-ball sized or smaller.
• Flea beetles — Beetles riddle seedling leaves with small holes, checking growth. Cover with fine mesh, keep plants well watered, and sow into warm soil for fast establishment.
• Cabbage root fly — Larvae feed on roots, wilting and stunting young plants. Fit brassica collars around stems at transplanting or use insect-proof mesh to block egg-laying.
• Bolting — Cold checks to young plants or hot, dry spells can trigger premature flowering before the bulb forms. Sow into warm conditions and keep growth steady and unstressed.

Propagation

From seed. Sow direct and thin, or sow in modules and transplant, from spring to late summer at 10-20°C, spacing plants 25-30 cm apart. Make small successional sowings every 3-4 weeks for a continuous supply. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Kohlrabi is pet-safe. Kohlrabi is a Brassica oleracea vegetable, not listed on the ASPCA toxic-plant list and within the group of cruciferous vegetables the ASPCA considers safe for dogs and cats in moderation. As with all brassicas, large amounts can cause gas and GI upset, so feed only small, occasional portions. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Kohlrabi deep-dive guides

Every aspect of kohlrabi care, each with its own calibrated guide:

• Kohlrabi watering schedule
• Kohlrabi light requirements
• Best soil mix for kohlrabi
• Kohlrabi fertilizing guide
• When to repot kohlrabi
• How to propagate kohlrabi
• Kohlrabi growth rate & size
• Kohlrabi cold hardiness
• Kohlrabi temperature & humidity
• Is kohlrabi toxic to cats & dogs?
• Is kohlrabi toxic to cats?
• Is kohlrabi toxic to dogs?

Featured in these plant shortlists

Kohlrabi qualifies for 1 curated Growli shortlist — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best pet-safe low-maintenance plants — Non-toxic to cats and dogs and forgiving of forgotten watering — the easiest safe choices for a busy pet household.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Kohlrabi is also commonly called German turnip or Turnip cabbage.

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