Kohlrabi is a member of the brassica family that originated in Northern Europe. Crazy to think that this crop didn’t make it to America until the 1800s. Also, if you survey people who are not gardeners, I am willing to bet almost anything that more than 85% would say they have never seen or tasted kohlrabi.
Since Kohlrabi is a member of the brassica family, that means that it is related to kale, broccoli, and brussels to name a few. Members of the brassica family are referred to as cole crops. Read about cole crops here.
The name kohlrabi is German. “Kohl” means cabbage, and “ Rabi” means turnip; therefore, kohlrabi is a cabbage turnip, and that is exactly how it grows. It bulbs like a turnip, except it is above ground.
Kohlrabi, like other cole crops, is a cool-season crop, but here in the south, they can also be grown in the spring. They thrive in nutrient-rich, fertile soil. They can be started from seed or transplant and takes 45-60 days to complete the cycle. For a fall crop, direct seed or plant out in midsummer and for a winter crop plant or seed in the fall. Paying attention to the ideal planting time is crucial for this crop to succeed. You do not want to plant when the average temperatures are over 80F. You will notice that heat is directly correlated to taste. Kohlrabi allowed to mature during the colder season has a sweeter taste than spring kohlrabi.
When planting in a row allow 4-8” spacing between plants and 12-18” spacing between rows. I have noticed that these seedlings transplant well, so if you overseed your rows or area, do not just chop, thin, and throw away. You have the option of digging up the seedlings and re-potting or moving to other places in the garden. Do not think you have to be confined to growing kohlrabi in your garden beds. This crop does exceptionally well when planted in a container.
Like most members of the cole crops and brassica family they are suckers for nitrogen. Is transplanting starts than apply a nitrogen-rich fertilizer at planting. If direct seeding, wait to apply the fertilizer until 2-4 weeks after the seeds have sprouted. Reapply apply fertilizer every 2-4 weeks.
The bulb is ready to harvest when it reaches 2-3” in diameter. The longer it goes, the more fibrous the flesh becomes. Like other members of the brassica family, the leaves are edible and have the best flavor when they are young.