Your kohlrabi not forming bulbs likely comes down to one of four main causes. Temperature stress, uneven watering, overcrowding, or poor soil can all stop bulb growth. These kohlrabi growing problems are fixable once you know what to look for.
When I first grew kohlrabi, my plants made lots of leaves but the stems stayed thin. I had packed them too close and they fought for space. After I learned to thin them out to 4-6 inches apart, my next batch formed perfect round bulbs.
The kohlrabi bulb is not a root or fruit. It is a swollen stem that grows above ground. You need steady conditions for success. Kohlrabi bulb development stalls when the plant hits stress. It puts energy into survival instead of making that fat stem you want.
Heat and cold top the list of concerns. Cold below 45°F (7°C) for too long makes plants bolt instead of bulb. Heat above 80°F (27°C) slows growth and turns bulbs woody. Kohlrabi troubleshooting often starts with checking temps. Time your planting for mild weather.
USU Extension notes that water problems create tough fibrous bulbs. Letting your soil dry out then flooding it stresses the plant. The stem cannot expand in smooth layers. You end up with cracked or woody results. Keep moisture even with 1 inch of water per week.
Overcrowding starves plants of what they need to bulk up. Each kohlrabi needs room for roots to spread and gather nutrients. Packed rows mean smaller bulbs for everyone. Thin your seedlings early or start them in cells you transplant at proper spacing.
Poor soil might be your problem if you have ruled out the others. Kohlrabi wants fertile ground with good drainage. Heavy clay holds too much water. Sandy soil dries out fast. Add compost before planting to fix either issue and give your plants a better start.
I helped a friend last season figure out why her kohlrabi failed. We checked her spacing first which looked fine. Then I asked about watering. She had been using a sprinkler on random days. We set up drip irrigation on a timer and her fall crop came out great.
Check each factor one by one to find your answer. Look at your plant spacing first since that is easy to spot. Feel the soil to check water levels. Note recent temps in your area. The cause is usually simple once you start this kohlrabi troubleshooting process.
Read the full article: Growing Kohlrabi: Beginner-Friendly Guide
