Kohlrabi: Sowing, planting and harvest calendar
How do you sow kohlrabi under cover?
Sow your kohlrabi under cover in spring if you want an early crop or the garden soil is still cold and heavy. Choose a variety suited to the season and sow small batches so the plants do not all reach the same stage together. Prolonged cold can encourage flowering instead of the swollen stem you want.
Use a clean module tray or pots with drainage holes, filled with fine, free-draining seed compost. Moisten it before sowing two seeds per cell about 1 to 1.5 cm deep, following the seed packet where needed. Cover and water gently. Maintain even moisture without standing water and place the containers in a bright sheltered space, protected from cold spells and overheating.
After emergence, keep one vigorous seedling per cell by cutting away the weaker one. Provide plenty of light to avoid stretched stems. Check root development without breaking up the balls and do not leave plants ageing in small containers. Harden them off gradually before planting in sufficiently mild weather while they are still small, around 5 cm tall. Preserve the root balls to minimise checks in growth.
How do you sow kohlrabi outdoors?
Sow your kohlrabi directly in the garden in spring or summer, choosing a variety suited to that season. In spring, wait for sufficiently mild conditions: prolonged cold can encourage bolting. In summer, avoid very hot, dry spells if you cannot maintain soil moisture. Small batches sown at intervals help spread the harvest.
Choose a sunny position with fertile, well-drained soil that can retain moisture. Weed thoroughly, remove large clods and level the surface. Make a drill about 1 to 1.5 cm deep, moisten its base and sow thinly. Cover with fine soil, firm lightly and water with a gentle spray so the seeds stay in place.
Keep the seedbed moist until emergence. Once seedlings are easy to handle, thin gradually to the spacing recommended for your variety, often around 15 to 30 cm. Larger cultivars need more room; this distance is not the sowing depth. Watch for slugs and use insect mesh against cabbage pests if needed. Weed by hand close to young plants and avoid gaps in watering that slow their growth.
How do you plant and grow kohlrabi?
Plant your kohlrabi while it is still young and well rooted, without waiting for it to grow tall in its pot. Plants around 5 cm high generally establish better than overgrown ones. Gradually harden off any raised under cover. Choose mild conditions without a prolonged cold spell forecast, since a sharp chill can encourage flowering before the stem swells.
Prepare a sunny position with fertile, well-drained soil that retains moisture. Remove weeds before planting and add well-rotted compost if needed. Water the root balls so you can remove them from their cells without crumbling them. Make a hole just large enough for each intact root ball.
Set the plants at their previous growing depth, without burying the stem base where the swelling will form. Fill in, firm gently by hand and water to settle soil around the roots. Follow the cultivar’s spacing, often around 15 to 30 cm, allowing more room for larger varieties.
Maintain consistent moisture during establishment without waterlogging. Protect young leaves from slugs and, where needed, cabbage insects with suitable mesh. Check that growth resumes and weed carefully nearby rather than hoeing against the stems.
How to care for this plant
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Maintain the mulch
Once the plants are established and the soil has warmed, check the mulch and top up bare patches if needed. Keep the stem bases clear and remove weeds before covering them.
When do you harvest kohlrabi?
Harvest your kohlrabi while its swollen stem is still tender and has reached the size appropriate for the variety. For many ordinary types, a diameter of around 5 to 8 cm is a useful guide, but giant cultivars have different criteria. The edible part is a thickened stem above ground, rather than a root that should keep growing indefinitely.
Check plants regularly instead of waiting for a single date. The harvest season depends on sowing time, climate and variety. In hot, dry weather, leaving stems too long can make the flesh more fibrous. Start with the largest plants and let smaller ones continue growing if conditions remain favourable.
Cut beneath the swelling with a clean, sturdy knife while supporting the kohlrabi. Avoid pulling to tear the edible part away from its root. Remove leaves to reduce water loss during storage; healthy young leaves can be used separately. Refrigerate intact swollen stems, protecting them from drying out, for example in a perforated bag. Check regularly and use damaged but sound ones first. Discard rotting parts and do not expect long storage in a dry room.
Kohlrabi
- Type : Vegetables
- Subtype : Leafy vegetables
- Botanical Family : Brassicaceae (cruciferous)
Characteristics
- Lifecycle : Annual
- Exposure : Full Sun
- Frost Hardiness : Frost Resistant
- Cultivation Difficulty : Medium
- Mature height : 30 cm
Sowing & Planting
- Greenhouse Growing : Not Required
- Sowing Depth : 0.5 cm
- Plant Spacing : 20 cm
- Row Spacing : 30 cm
Maintenance
- Maintenance : Low
- Water Requirements : Moderate
Other characteristics
- Soil Type : Humus-rich
- Soil pH Preference : Neutral
- Pest Sensitivity : Moderate
- Disease Sensitivity : Moderate
- Weed Sensitivity : Moderate
- Pollination : Insect-pollinated
- Propagation : Sowing