Kohlrabi reward good timing in a Zone 8 garden: sow at the right moment and the harvest is heavy; sow wrong and it disappoints. This guide answers when to plant kohlrabi zone 8 in full: sowing, transplant and harvest windows for USDA Zone 8, plus spacing, soil, water, companions, pests and storage.
Zone 8 covers areas with average annual minimum temperatures of 10 to 20°F, across the southern United States and the Pacific coast. The average last spring frost falls in the Mar 1–15 range and the average first autumn frost in the Nov 15–Dec 1 range. These are USDA zone averages, not exact dates for any one garden — check your local extension service and the forecast before planting tender crops outside. The frost-free season runs roughly eight months, from mid-March into mid-November, which is one of the longest in the country.
When to plant kohlrabi in Zone 8
Kohlrabi are frost-tolerant, which makes them one of the most flexible crops in the Zone 8 garden. They grow through the cool months, tolerate light frosts, and in many Zone 8 winters keep producing long after summer crops have finished. The autumn sowing is often the best one. Kohlrabi take 50–60 days to reach maturity, so work backwards from the frost dates to place each stage of the season.
The table below puts the whole season on one page, worked back from the Zone 8 frost averages (Mar 1–15 last frost, Nov 15–Dec 1 first frost) and 50–60 days to maturity. Use the frost date calculator to check the averages for your own area, and confirm them with your local extension service.
| Stage | Zone 8 window | Notes |
|---|---|---|
| Start indoors | Feb–Mar, or Jul–Aug for autumn | Germination takes 7–10 days |
| Direct sow outdoors | Feb–Apr spring; Aug–Sep autumn | Sow into moist, prepared soil |
| Transplant outdoors | Mar–Apr or Aug–Sep | Harden seedlings off first |
| First harvest | 50–60 days after sowing; pick at tennis-ball size | 50–60 days to maturity |
| Second sowing | Autumn crop sown Aug–Sep | Count back from the first frost |
Starting and planting
Kohlrabi can be started indoors or sown directly. Starting indoors gives the earliest crop; direct sowing is simpler. Start seed indoors in February or March, or direct-sow in February to April. Sow again in August or September for an autumn crop, which is often the better of the two in Zone 8.
Fork the bed over, remove weeds and stones, and dig in well-rotted compost before sowing. Kohlrabi grow best at a soil pH of 6.0–7.5 — test your soil through your local extension service before amending it. Early White Vienna is a fast, mild kohlrabi for spring and autumn. Plan the bed with the Seed Starting Calculator so each sowing lands in its window.
Spacing, sun and soil
Space plants 6–9 inches apart. Crowded plants stay small and invite disease through poor airflow, so thin seedlings to the final spacing once established.
This crop needs full sun — at least six hours of direct sun a day, and more is better. In Zone 8, a south-facing bed or an open spot away from trees and fences gives the strongest growth and the best flavour. Soil should be deep, fertile and free-draining, with a pH of 6.0–7.5; heavy clay improves with compost, and raised beds help where drainage is poor.
Watering
Water needs are moderate: aim for steady, even moisture rather than feast-and-famine watering. About an inch of water a week from rain or irrigation is a useful guide in most Zone 8 summers, more in hot, dry spells. Water at the base in the morning and mulch to hold moisture.
Companion planting
Good companions for kohlrabi include marigolds, basil, onions, lettuce. Planting companions nearby can help with pest confusion, pollination and making the most of bed space. The companion planting finder can suggest combinations for your whole bed. Rotate crops each season, and avoid planting kohlrabi where others of the same family (Brassicaceae) grew last year.
Common pests and problems
Watch for cabbage worms, aphids, flea beetles, slugs.
- Cabbage Worms — inspect weekly; hand-pick or wash off with water, and encourage natural predators.
- Aphids — inspect weekly; hand-pick or wash off with water, and encourage natural predators.
- Flea Beetles — inspect weekly; hand-pick or wash off with water, and encourage natural predators.
- Slugs — inspect weekly; hand-pick or wash off with water, and encourage natural predators.
Beyond pests, the main problems are weather-related: a late frost, drought at a critical stage, or waterlogged soil after heavy rain. Cover tender plants with frost cloth if a late frost threatens, and mulch to even out soil moisture.
Harvest and storage
Pull kohlrabi when the swollen stem is about the size of a tennis ball, at 50–60 days. Left to grow larger it turns woody, so check often and harvest on time.
The classic Zone 8 mistake with kohlrabi is letting the bulbs grow too big. Oversized kohlrabi is woody and tough — harvest at tennis-ball size, even if it feels early.
For storage, pick in the morning when plants are crisp and cool, and handle the harvest gently.
Frequently asked questions
When should I plant kohlrabi in Zone 8?
Work from the table above, using the average last frost (Mar 1–15) and first frost (Nov 15–Dec 1), with 50–60 days to maturity. These are averages, not exact dates — check your local extension service before planting.
How much sun do kohlrabi need in Zone 8?
Full Sun — at least six hours of direct sun a day. Give them the sunniest spot you have.
What soil pH do kohlrabi prefer?
A pH of 6.0–7.5. Test your soil before amending it, and add compost to improve structure whatever the pH.
What pests attack kohlrabi in Zone 8?
The most common are cabbage worms, aphids, flea beetles, slugs. Inspect weekly, hand-pick larger pests, wash small ones off with water, and keep the bed clean and well spaced.
What part of kohlrabi do you eat?
The swollen stem above the ground, peeled and eaten raw or cooked. The leaves are edible too, cooked like other brassica greens.
Browse the full planting calendar. For the same crop in a colder zone, see when to plant kohlrabi in Zone 7, and for a related crop, when to plant rutabaga in Zone 8.