Kohlrabi is the odd-looking brassica that tastes like a mild, sweet turnip — and it is one of the easiest cool-season crops for Zone 7. This guide covers when to plant kohlrabi zone 7 in detail: the sowing, transplanting and harvest windows for USDA Zone 7, plus spacing, soil, water, companions, pests and storage — all based on USDA zone averages and standard published crop ranges.
Zone 7 covers areas with average annual minimum temperatures of 0 to 10°F. The average last spring frost falls in the Mar 15–Apr 1 range and the average first autumn frost in the Nov 1–15 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 seven months, from late March into early November,
When to plant kohlrabi in Zone 7
Start kohlrabi indoors in February to March, or direct-sow in March to April, for a spring crop ready in 50–60 days. It is frost-tolerant, so it goes out around the last frost without fuss. A second sowing in August gives autumn bulbs that mature in October.
The table below puts the whole season on one page. All dates are ranges worked back from the Zone 7 frost averages (Mar 15–Apr 1 last frost, Nov 1–15 first frost) and the crop's published days to maturity (50–60 days). Use the frost date calculator to check the averages for your own area, and confirm them with your local extension service.
| Stage | Zone 7 window | Notes |
|---|---|---|
| Start indoors | Feb–Mar for spring; July for autumn | Germination takes 7–10 days |
| Direct sow outdoors | Mar–Apr, and Aug for the autumn crop | Sow into moist, prepared soil |
| Transplant outdoors | Apr, after the last frost | Harden seedlings off first |
| First harvest | May–July and Oct, 50–60 days after sowing; pick at tennis-ball size | 50–60 days to maturity |
| Autumn / second sowing | Sow in Aug for autumn bulbs | Count back from the first frost |
Starting and planting
Space plants 6–9 inches apart in rows about a foot apart, in soil with a pH of 6.0–7.5. Kohlrabi needs steady moisture while the bulb swells — drought gives woody, cracked bulbs — so water in dry spells and mulch to hold moisture.
Before sowing, fork the bed over, remove weeds and stones, and dig in well-rotted compost. Kohlrabi grows best at a soil pH of 6.0–7.5 — test your soil through your local extension service before amending it.
Spacing, sun and soil
Space plants 6–9 inches apart. Crowded plants compete for light, water and nutrients, stay small, and invite disease through poor airflow, so thin seedlings to the final spacing once they are established.
This crop needs full sun — at least six hours of direct sun a day, and more is better. In Zone 7, 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 organic matter, 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 7 summers, more in hot, dry spells. Water at the base of the plant in the morning, mulch to hold moisture, and avoid wetting the leaves, which invites disease.
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 — marigolds, for example, are a classic companion across the vegetable garden. The companion planting finder can suggest combinations for your whole bed. Avoid planting kohlrabi where others of the same family (Brassicaceae) grew last year: rotate crops each season to reduce soil-borne disease and pest build-up.
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 after transplanting, 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
Harvest when the bulbs are about the size of a tennis ball, 50–60 days after sowing. Picked young, kohlrabi is crisp and sweet; left to grow large, it turns woody. Cut the bulb with its leaves attached, and use the leaves too — they cook like collards.
Kohlrabi keeps for several weeks in the fridge with the leaves removed, and autumn bulbs store in a cool, dark place. Peel before eating raw or cooking; the skin is tough even on young bulbs.
The classic Zone 7 mistake with kohlrabi is letting the bulbs grow too big. A tennis ball is the sweet spot — bigger bulbs are woody, and no amount of cooking fixes them.
Frequently asked questions
When should I plant kohlrabi in Zone 7?
Start kohlrabi indoors in February to March, or direct-sow in March to April, for a spring crop ready in 50–60 days. Work from the table above, using the average last frost (Mar 15–Apr 1) and first frost (Nov 1–15), with 50–60 days to maturity. 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.
How much sun does kohlrabi need in Zone 7?
Full Sun — at least six hours of direct sun a day where possible. Give it the sunniest spot you have.
What soil pH does kohlrabi prefer?
A pH of 6.0–7.5. Test your soil before amending it, and add compost to improve structure whatever the pH. Your local extension service can test a sample and recommend amendments.
What pests attack kohlrabi in Zone 7?
The most common are cabbage worms, aphids, flea beetles, slugs. Inspect plants weekly, hand-pick larger pests, wash small ones off with water, and keep the bed clean and well-spaced so air circulates.
How do I store kohlrabi after harvest?
Kohlrabi keeps for several weeks in the fridge with the leaves removed, and autumn bulbs store in a cool, dark place. Peel before eating raw or cooking; the skin is tough even on young bulbs.
See the Zone 7 September planting guide for what else to sow and plant in the same month, browse the full planting calendar, and try the Seed Starting Calculator to plan your dates. For a related crop, see when to plant bok choy in Zone 7.