Last Updated on September 17, 2026
How Many Kohlrabi Plants per Square Foot?
4 kohlrabi plants per square foot, in a 2×2 grid, about 6 inches apart. That is the spacing on my square foot gardening chart and in the Plan My Garden planner. Crowd them to 9 per square and the bulbs come in smaller. Give a giant storage variety a full block instead; its bulb alone can grow wider than the square.
The spacing pattern
| Per square foot | 4 plants, in a 2×2 grid |
|---|---|
| Inches apart | about 6 inches, plant to plant |
| 4 x 4 bed (16 squares) | up to 64 kohlrabi plants |
| 4 x 8 bed (32 squares) | up to 128 kohlrabi plants |
| 3 x 6 bed (18 squares) | up to 72 kohlrabi plants |
That is the number on my square foot gardening chart, and the Plan My Garden planner places kohlrabi the same way: 4 plants to each 1 x 1 foot cell. Utah State University Extension spaces kohlrabi 6 inches apart in the row, the number behind the grid.
The 4 vs 9 tradeoff
Extension guides do not all agree on one spacing, because spacing controls bulb size. University of Minnesota Extension thins spring kohlrabi to 4 inches between plants, 9 per square on the same grid math. Wisconsin Horticulture Extension (University of Wisconsin-Madison Division of Extension) and University of Illinois Extension give a wider window, 2 to 5 inches, spanning 9 per square at 4 inches up to 16 per square at 3 inches.
| Spacing | In a square | What you get |
|---|---|---|
| 6 in (Utah State University Extension) | 4 per square | Standard size bulbs, matches the chart and the planner |
| 4 in (University of Minnesota Extension, spring crop) | 9 per square | Smaller bulbs, more plants from the same bed |
| 2 to 5 in (Wisconsin Horticulture Extension, Illinois Extension) | 9 to 16 per square | Same tradeoff; pick the tighter end for baby kohlrabi |
The bed counts above are grid maximums. At 9 per square, a 4 x 4 bed holds up to 144 kohlrabi and a 4 x 8 bed holds up to 288, but every bulb will be smaller than the ones you get at 4 per square.
Harvest before it goes woody
The window for good eating is short, no matter the spacing. Utah State University Extension and University of Minnesota Extension both harvest at 2 to 3 inches in diameter; larger stems turn tough and woody. University of Illinois Extension fills in the curve: pulling starts around 1 inch across, runs best through 2 to 3 inches, and past 3 inches the stem develops woody fibers, especially low down. A 4 per square bulb and a 9 per square bulb go woody on the same schedule; the tighter spacing just starts you with a smaller bulb, so check the bed often once bulbs show.
It is a stem, not a root
The part you eat is not a root. Wisconsin Horticulture Extension calls it a turnip-like enlargement of the stem that forms above the soil, commonly called a bulb even though botanically it is not one. University of Illinois Extension and University of Minnesota Extension describe the same structure: an enlarged stem section just above the soil line, which is why kohlrabi is sometimes mistaken for a root vegetable. So set transplants, or thin seedlings, with the base of the stem at the soil surface, not mounded over or set deep the way you would a root crop like turnip.
Giant and storage kohlrabi need more room
The 4 and 9 per square counts are for standard kohlrabi, eaten within a few weeks of forming a bulb. A few varieties grow much larger without turning woody. Wisconsin Horticulture Extension lists ‘Gigante’ at up to a foot across and 25 pounds without woody fibers, and ‘Kossak’ at bulbs up to 10 inches across. The same source spaces standard kohlrabi 2 to 5 inches apart but says to go farther apart, or more, for these huge varieties. A bulb that wide needs more clearance than the grid gives it: on my chart’s own conversions, that is closer to a full 2×2 foot block, one plant to every 4 squares. University of Minnesota Extension adds that giant kohlrabi does best as a fall crop.
Planting the square
- The planner sows kohlrabi direct, 6 to 4 weeks before your last frost, with no indoor-start or transplant window for this crop.
- Sow seeds 1/4 to 1/2 inch deep, the depth Utah State University Extension, Wisconsin Horticulture Extension and University of Illinois Extension all use.
- Thin to the spacing you want: 6 inches for standard bulbs at 4 per square, or 4 inches for smaller bulbs at 9 per square.
- Water on a steady schedule, about 1 to 2 inches a week (Utah State University Extension); moisture swings, not just heat, push bulbs toward woody.
- For an earlier harvest, transplants can go out 1 to 2 weeks before your last frost instead (Utah State University Extension).
When to plant kohlrabi
These are the windows the Plan My Garden planner uses, counted from your average last spring frost. Turn the weeks into dates with the seed starting calendar, or enter your zip code on Plan My Garden.
| Start indoors | No indoor-start window in the planner; it treats kohlrabi as a direct-sow crop |
|---|---|
| Transplant out | No separate week in the planner; Utah State University Extension allows 1 to 2 weeks before your last frost |
| Direct sow | 6 weeks before to 4 weeks before your last frost |
| Days to maturity | about 55 days (Wisconsin Horticulture Extension: named varieties run 38 to 80 days) |
| Frost tolerance | Hardy (Plan My Garden planner). Utah State University Extension calls it the least frost-hardy cabbage-family crop it covers: hard frosts can damage young plants, and a cold stretch under 45°F can make a mature plant bolt instead |
Growing notes
Kohlrabi wants it cool: University of Minnesota Extension puts the best range at 65 to 75°F, and Utah State University Extension says growth suffers past 75°F. Heat and uneven watering both push bulbs toward tough and woody, on top of harvesting late. The leaves are edible too, per Utah State University Extension and University of Illinois Extension, so thinnings from a 9 per square planting do not go to waste.
Where to get seed
Wood Prairie carries organic Trero kohlrabi seed, an early white variety (42 days) that holds good quality to 6 inches across, though it is best picked around 3 inches. Code PMG5 takes 5 percent off.
Quick questions
How many kohlrabi plants fit in a 4×8 raised bed?
Up to 128 at the standard 4 per square, 6 inches apart. Crowd them to 9 per square, 4 inches apart, and the same bed holds up to 288, but the bulbs will be smaller.
What is kohlrabi spacing in square foot gardening?
4 plants per square, in a 2×2 grid, about 6 inches apart. That matches the Plan My Garden planner and Utah State University Extension’s 6 inch row spacing.
Can you plant kohlrabi closer together?
Yes. University of Minnesota Extension thins spring kohlrabi to 4 inches apart, which works out to 9 per square, and Wisconsin Horticulture Extension and University of Illinois Extension both allow spacing as tight as 2 inches. The tradeoff is smaller bulbs at harvest.
Do giant kohlrabi varieties need more space?
Yes. Wisconsin Horticulture Extension lists varieties such as ‘Gigante’ and ‘Kossak’ that reach 10 inches to a foot across without going woody, and says to space large varieties farther apart than the standard 2 to 5 inches. A bulb that size needs closer to a full 2×2 foot block than a shared square.
Let the planner place them
Not sure whether to run the standard 4 per square or crowd them tighter for baby bulbs? Plan My Garden is free to start: enter your zip code, draw your beds, pick kohlrabi and everything else you want to grow, and it places each plant at square-foot spacing and builds a planting schedule from your frost dates.
Related: Square Foot Gardening Chart · Seed Starting Calendar · Square Foot Garden Calculator · How Many Cabbage Plants per Square Foot? · How Many Cauliflower Plants per Square Foot? · How Many Turnip Plants per Square Foot?
