Kohlrabi Woody? Harvest Size and Heat Explained
The short answer
Kohlrabi woody and tough usually means the swollen stem grew too large or matured in heat. Iowa State Extension says to harvest at 2 to 3 inches across, since larger bulbs are usually tough and woody. Utah State Extension adds that hot weather makes the stem woody and tough. Grow it in cool spring or fall weather and water evenly.
Why is my kohlrabi woody?
Two causes stand out. First is size. Minnesota Extension says a bulb that gets too large turns tough, woody and bitter. Second is heat, which Utah State says makes the stem woody and tough. Minnesota Extension adds that heat or moisture stress makes bulbs fibrous and liable to crack. Read about stress in the effects of environmental stresses on weed plants.
What size should kohlrabi be at harvest?
Iowa State, Utah State and Minnesota Extension all point to 2 to 3 inches across. Wisconsin Extension notes you can begin at about an inch and continue until the variety reaches its mature size. Giant fall types such as Gigante are the exception, since Wisconsin says that bulb does not get woody.
How does heat change kohlrabi?
Kohlrabi thrives between 65 and 75°F, according to Minnesota Extension. Spring kohlrabi harvested in summer is more likely to turn fibrous if left to over mature. Overheated plants turn bitter too. Utah State notes that temperatures below 45°F can make plants flower, so timing cuts both ways. See cannabis heat stress.
Kohlrabi basics
| Factor | Target | Notes |
|---|---|---|
| Harvest size | 2 to 3 inches | Larger turns woody |
| Temperature | 65 to 75°F | Cool seasons |
| Water | About 1 inch a week | Even moisture |
| Spacing | 6 inches in rows 1 foot apart | Utah State |
| Spring types | 35 to 45 days | Minnesota Extension |
Sources: Iowa State University Extension, Utah State University Extension, University of Minnesota Extension, University of Wisconsin Extension.
How to: step by step
- Sow in early spring or late summer.
- Hold soil evenly moist. Check depth by feel with checking soil moisture by feel.
- Mulch to hold moisture and cool the soil.
- Check stems weekly as they swell.
- Harvest at about 2 to 3 inches across.
- Sow small batches for a steady supply.
Troubleshooting
Woody stem: late harvest. Pick smaller.
Split stem: uneven watering. Water evenly.
Fibrous texture: heat. Grow in cool seasons.
Kohlrabi grows fast, so timing counts. Kind Seed Co shares more vegetable notes on the blog.
Sources
- When should I harvest kohlrabi?, Iowa State University Extension
- How to grow kohlrabi in your garden, Utah State University Extension
- Growing kohlrabi in home gardens, University of Minnesota Extension
- Kohlrabi, University of Wisconsin Extension
FAQ
Can you eat woody kohlrabi?
Woody kohlrabi is edible, just tough. Iowa State Extension says bulbs larger than 3 inches are usually tough and woody, and Minnesota Extension adds they can turn bitter. The leaves are still tasty as cooking greens, so a late harvest is not a total loss.
Are some kohlrabi types tender when large?
Yes. Wisconsin Extension lists Gigante as a fall type with a bulb up to a foot across that does not get woody. Minnesota Extension advises growing giant kohlrabi as a fall crop. Standard types still need picking at 2 to 3 inches.
Should you peel kohlrabi?
The sources here don't say whether to peel. Wisconsin Extension notes purple types only have colored skin and white flesh inside. Minnesota Extension suggests serving kohlrabi raw, sliced into salad, grated into slaw or cooked in stir fries.
How fast does kohlrabi grow?
Quickly. Utah State Extension lists Quickstar at 40 days and Grand Duke at 50 days. Wisconsin Extension lists Eder at 38 days. Minnesota Extension suggests spring varieties with 35 to 45 days to harvest so they mature before summer heat.
Why did my kohlrabi crack?
Stress is usually the cause. Minnesota Extension says plants that are overheated or short of water produce bitter compounds, and the bulbs can turn fibrous and crack. About an inch of water a week and steady growth help prevent it.
