Kohlrabi Spring Planting Guide: Timing, Soil Prep & Succession Planting

Kohlrabi is one of the best spring vegetables you can grow. It’s fast (45-60 days from seed to harvest), tolerates cool weather, and actually prefers the conditions that early spring provides. But timing matters more than most gardeners realize — plant too late and rising temperatures will make your kohlrabi woody, bitter, or bolt to seed before the bulb sizes up.

Here’s how to plan your spring kohlrabi planting for the best results.

When to Plant Kohlrabi in Spring

Kohlrabi is a cool-season crop. It germinates in soil as cold as 40°F (4°C), though 60-70°F (15-21°C) is optimal. The bulbs develop best when daytime temperatures stay between 50-75°F (10-24°C). Once temps consistently hit 80°F+, quality drops fast.

By USDA Hardiness Zone

Zone	Start Seeds Indoors	Direct Sow Outdoors	Transplant Outdoors
3-4	Mid-March	Late April–Early May	Late April
5-6	Early March	Mid-April	Mid-April
7-8	Mid-February	Mid-March	Mid-March
9-10	January	Late February	Late February

These are guidelines — your local microclimate matters. The key benchmark: you can transplant kohlrabi outdoors 2-4 weeks before your last expected frost date. Established kohlrabi seedlings tolerate light frosts down to about 25°F (-4°C).

The Critical Window

Spring kohlrabi needs to reach harvest size before summer heat arrives. Since most varieties take 45-60 days from transplant (or 55-70 from direct sowing), count backward from when your area typically hits sustained 80°F+ days. That’s your deadline for getting plants in the ground.

For example, if summer heat reliably arrives in mid-June in your area, you’d want transplants in the ground by mid-April at the latest — giving them a full 60 days of cool growing weather.

Choosing Spring Varieties

Not all kohlrabi varieties perform equally in spring. For spring planting, prioritize:

• Early-maturing varieties — Look for 40-55 day varieties to beat the heat
• Bolt resistance — Some varieties are bred to resist premature flowering in fluctuating spring temperatures

Reliable spring performers include:

• Early White Vienna — The classic, 55 days, widely available
• Early Purple Vienna — Same timing, purple skin, white flesh
• Kolibri — Excellent hybrid, 45 days, very bolt-resistant
• Kossak — If you want large bulbs, this one sizes up to 8-10 inches while staying tender
• Quickstar — Very fast at 40-45 days, ideal for short spring windows

For a full rundown of variety options, see our kohlrabi varieties guide.

Soil Preparation

Kohlrabi isn’t fussy, but good soil prep makes a noticeable difference in bulb size and texture.

Soil Requirements

• pH: 6.0-7.5 (slightly acidic to neutral)
• Type: Loose, well-draining, fertile. Heavy clay compacts around the developing bulb and restricts growth.
• Organic matter: Work in 2-3 inches of compost before planting. This improves drainage in clay soils and water retention in sandy soils.

Spring Soil Prep Steps

1. Test your soil — A basic pH and nutrient test tells you what amendments are needed. Most extension offices offer cheap or free testing.

2. Work the bed as early as possible — As soon as the ground thaws and isn’t waterlogged, turn or loosen the top 8-10 inches. Kohlrabi’s root system is relatively shallow, but loose soil encourages the bulb to expand freely.

3. Add compost — Spread 2-3 inches of finished compost and work it into the top 6 inches. This is the single most impactful thing you can do for kohlrabi quality.

4. Apply a balanced fertilizer — Use a 10-10-10 or similar balanced granular fertilizer at planting time, worked into the soil. Kohlrabi is a moderate feeder — it doesn’t need heavy fertilization, but it shouldn’t struggle for nutrients either.

5. Ensure drainage — If your soil stays soggy after rain, consider raised beds or mounded rows. Kohlrabi in waterlogged soil develops root rot and never sizes up properly.

If you’re growing in containers, our growing kohlrabi in containers guide covers soil mix and pot size recommendations.

Starting Seeds Indoors

Starting seeds indoors gives you a 3-4 week head start and more control over timing.

How to Start Kohlrabi Indoors

1. Timing: Start seeds 4-6 weeks before your planned transplant date.

2. Containers: Use cell trays, small pots, or soil blocks. Kohlrabi doesn’t need deep containers at this stage — 2-3 inches of depth is fine.

3. Planting depth: Sow seeds 1/4 to 1/2 inch deep. Cover lightly with seed starting mix.

4. Temperature: Keep soil at 65-75°F (18-24°C) for fastest germination. Seeds typically sprout in 3-7 days at this range. A heat mat helps in cold rooms.

5. Light: Once seedlings emerge, they need strong light — 14-16 hours under grow lights, positioned 2-4 inches above the plants. Insufficient light produces leggy, weak seedlings.

6. Thinning: If you sowed multiple seeds per cell, thin to one seedling per cell once the first true leaves appear. Snip extras at soil level rather than pulling to avoid disturbing roots.

7. Hardening off: Starting 7-10 days before transplant, gradually expose seedlings to outdoor conditions. Day 1-2: a few hours in sheltered shade. Day 3-5: longer periods with some direct sun. Day 6-10: full outdoor exposure, including overnight if temps are above 30°F.

Transplanting Outdoors

• Spacing: Set transplants 6-8 inches apart in rows 12-18 inches apart. Crowded kohlrabi produces undersized bulbs.
• Depth: Plant at the same depth they were growing in their containers — don’t bury the stem.
• Water: Water thoroughly at transplanting and keep soil consistently moist for the first week.
• Frost protection: If a hard freeze (below 25°F) threatens after transplanting, cover with row cover or cloches. Light frosts are fine.

For the full growing playbook, our how to grow kohlrabi guide covers everything from planting through harvest.

Direct Sowing in Spring

Direct sowing is simpler and works well if your spring is long enough.

1. When: Sow outdoors 2-4 weeks before the last frost date, once soil temperature is at least 40°F (faster germination at 60°F+).
2. How: Sow seeds 1/4-1/2 inch deep, spacing seeds 1 inch apart in rows 12-18 inches apart.
3. Thinning: Once seedlings have 2-3 true leaves, thin to 6-8 inches apart. Eat the thinnings in salads — they’re delicious.
4. Keep moist: Spring sun and wind can dry out surface soil fast. Water lightly but consistently until plants are established.

Direct-sown kohlrabi typically reaches harvest 7-14 days later than transplants started on the same date, since those indoor weeks count.

Succession Planting for Extended Harvest

Here’s the strategy most gardeners miss: instead of planting all your kohlrabi at once, stagger plantings every 2-3 weeks. This gives you a steady supply of perfectly sized bulbs instead of 20 kohlrabi all ready on the same Tuesday.

Spring Succession Planting Schedule

For a zone 6 garden (adjust dates for your zone):

Planting	Method	Date	Expected Harvest
#1	Transplant (started indoors Feb 15)	March 25	Mid-May
#2	Direct sow	April 10	Early June
#3	Direct sow	April 25	Mid-June
#4	Direct sow (heat-tolerant variety)	May 10	Late June–Early July

Three to four succession plantings usually covers the entire spring window. For planting #4, choose the most bolt-resistant variety you have — it’ll face the warmest conditions.

How Many Plants Per Succession?

A single kohlrabi bulb typically weighs 5-10 ounces at harvest. If your household eats kohlrabi twice a week, plant 6-8 plants per succession. For heavier kohlrabi users, go 10-12. Each planting takes up very little garden space — 8 plants need roughly 4 square feet.

Companion Planting

Spring kohlrabi plays well with many common garden vegetables. Good companions include beets, onions, lettuce, herbs like dill and thyme, and bush beans.

Avoid planting near strawberries, tomatoes, or pole beans — these are generally poor neighbors for brassicas.

Our kohlrabi companion planting guide has the complete list of good and bad companions with reasoning for each.

Common Spring Planting Problems

Bolting (Going to Seed)

The #1 spring kohlrabi problem. Causes:

• Transplanting seedlings that are too old or root-bound
• Extended cold snap after transplanting (vernalization triggers flowering)
• Planting too late and hitting summer heat

Prevention: Use bolt-resistant varieties, transplant young seedlings (4-5 weeks, not 7-8), and time plantings to mature before heat arrives.

Cracked or Woody Bulbs

Usually caused by inconsistent watering — the bulb swells rapidly after a dry period and the outer layers split. In spring, this often happens during the transition from cool, wet weather to warm, dry weather. Mulch around plants and water consistently (1-1.5 inches per week).

Small Bulbs

Crowding and poor soil fertility are the usual culprits. Thin aggressively (6-8 inch spacing minimum) and make sure you worked in compost and fertilizer at planting time.

Flea Beetles

These tiny jumping beetles chew small holes in leaves and love brassicas. They’re worst in spring when the weather warms up. Row cover is the most effective organic control — drape it over plants right after transplanting or direct sowing.

Harvesting Spring Kohlrabi

Spring kohlrabi is at its best when bulbs are 2-3 inches in diameter. Larger is possible with some varieties (Kossak can go 8-10 inches), but most standard varieties get woody and fibrous past 4 inches.

Check out our when to harvest kohlrabi guide for detailed timing and size recommendations.

Harvest in the morning when bulbs are coolest and most crisp. Cut the bulb from the root at soil level, remove leaves (save them for cooking), and refrigerate promptly. Spring kohlrabi stores well in the fridge for 2-3 weeks.

Planning Ahead: Fall Planting

If spring kohlrabi goes well, plan a fall crop too. Fall planting is actually easier in many climates — the plants grow into cooling weather rather than racing against warming weather. Kohlrabi touched by light frost is sweeter than any spring harvest.

Our guide to growing kohlrabi in winter covers late-season and cold-weather growing strategies.

Quick Reference: Spring Planting Checklist

• Choose early-maturing, bolt-resistant varieties
• Start seeds indoors 4-6 weeks before transplant date
• Prepare soil: compost, balanced fertilizer, loose texture
• Harden off seedlings for 7-10 days
• Transplant 2-4 weeks before last frost, space 6-8 inches
• Plan 2-3 succession plantings, 2-3 weeks apart
• Mulch and water consistently (1-1.5 inches/week)
• Cover with row cover if flea beetles appear
• Harvest at 2-3 inches diameter for best quality

Spring kohlrabi rewards good timing more than anything else. Get the schedule right, keep the soil fed and watered, and you’ll be harvesting crisp, sweet bulbs from May through June with very little fuss.