Root & Relay

Growing guide

Kohlrabi Growing Guide

Brassica oleracea var. gongylodes

Choose a suitable green or purple cultivar, establish it in fertile well-drained soil, keep growth steady, protect young plants from brassica pests, and harvest before the swollen stem becomes woody.

Cool-season crop for local seasonal window; use local frost, heat, and day-length patterns to time plantings rather than a fixed calendar.

For planting dates, weather, and guidance tailored to your garden, ask Karpos.

Ask Karpos
Light
Full sun to light partial shade
Temperature
Cool-season crop; avoid prolonged heat
EC context
Use soil testing before nutrient corrections
Local planning
Use Karpos for location-specific timing and conditions.

Planting and setup

Start with the right setup

Choose the site, soil, timing, and growing approach before the season begins.

Choose a cultivar

Green types are often quick and mild, while purple types add color and may differ in maturity speed. Use a compact cultivar for containers or tighter beds.

Time the crop for cool weather

Sow in early spring or late summer for a fall crop. In hot regions, avoid the hottest part of the season and plan harvest before sustained heat.

Sow or transplant

Direct sow about 1/4 to 1/2 inch deep, or use sturdy transplants for an earlier crop. Thin seedlings when they have several true leaves.

Prepare fertile soil

Work finished compost into loose, well-drained soil before planting. Avoid planting into compacted ground or a bed that stays saturated.

Give stems room

Use spacing that lets the swollen stems expand and keeps leaves open to airflow. Remove weeds while plants are small.

Plan more than one sowing

Make small plantings every 2 to 3 weeks during the suitable season so harvests are staggered and stems are less likely to become oversized.

Start here

Quick-start conditions

Use these as practical starting points, then adjust for cultivar, container, weather, and measured plant response.

Light
Full sun supports rapid growth, while light partial shade can help in hot conditions.
Temperature
Kohlrabi prefers cool weather. Heat slows growth and can make the swollen stem tough; severe cold can trigger flowering.
Soil or media
Use fertile, loose, well-drained soil with organic matter. Test soil before making major nutrient corrections.
Water
Keep the shallow root zone evenly moist. Moisture swings can reduce quality and increase toughness or splitting.
Spacing
Thin or transplant commonly to about 6 inches apart in rows about 12 inches apart, adjusting for cultivar size.
Harvest
Harvest when the swollen stem is about 2 to 3 inches across. Young leaves are edible, too.

Seasonal care

Keep the crop on track

Timing shifts with cultivar, climate, and crop stage, so use these as seasonal checkpoints.

Keep seedbeds evenly moist and protect young plants from flea beetles and other early brassica pests.

Water consistently, maintain access around each plant, and feed only when soil testing or visible growth indicates a need.

Check stem size frequently. Harvest smaller stems for the best texture and use the leaves while they are fresh.

Use row covers when frost or insect pressure requires protection, while allowing enough ventilation to keep foliage dry.

As temperatures rise, watch for bolting, slower stem expansion, and tougher texture. Harvest promptly or replace aging plants.

Why it matters

What Root & Relay Watches

  • stem size and textureOversized kohlrabi develops more fiber. Check the swollen stem often and harvest while it is still firm and tender.
  • moisture and growth rateDry soil or nutrient stress interrupts rapid growth and can reduce eating quality. Check below the mulch before watering.
  • cabbageworms and loopersBrassica caterpillars chew holes in the leaves and reduce the plant area needed to expand the stem.
  • flea beetles and aphidsSmall plants are especially vulnerable to shot holes or distorted new growth. Inspect leaf undersides and growing points.
  • bolting and disease pressureExtreme cold, heat, crowding, wet foliage, and repeated brassica planting can reduce quality or increase problems.

Functional utility & care

Simple Routine

  • Record cultivar, sowing or transplant date, spacing, bed location, and expected maturity window.
  • Check soil moisture, stem expansion, new leaves, leaf undersides, and the crown several times each week.
  • Keep mulch clean, remove weeds while small, and maintain airflow around the canopy.
  • Inspect for caterpillars, flea beetles, aphids, disease symptoms, and signs of bolting before choosing a control.
  • Harvest stems while they are still tender, remove leaves for separate use, and refrigerate promptly.

Decision support

When Karpos Can Help

  • Which kohlrabi type fits my space and harvest timeline?
  • Is this kohlrabi growing fast enough for a tender stem?
  • Are these leaf holes from flea beetles, cabbageworms, or another pest?
  • Is the plant bolting because of temperature stress?
  • When should I harvest this swollen stem?

Research notes

Evidence and sources

These are source-attributed starting points for soil, raised-bed, and home-garden decisions. Hydroponic nutrient-solution references are intentionally excluded from this soil guide. This page is not a substitute for a local soil, water, or plant-health diagnosis.

Evidence: source-attributed brassica and home-garden guide reviewed Last reviewed: 2026-09-19