Kohlrabi can be an intimidating vegetable if you haven’t been around it much. It looks like a leafy, green space alien, and has a taste like fresh, crunchy broccoli or cauliflower stems, with a hint of radish.
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History of Growing Kohlrabi
The name kohlrabi comes from the German words kohl, meaning cabbage, and rabi, meaning turnip—and that kind of says it all about this odd-looking, delicious vegetable.
Although these green bulbs look like they were dug up from the earth, kohlrabi is actually a swollen stem that grows above ground. Kohlrabi—or “rabi” for the hip, urban foodie set—is widely used in Central Europe and Asia, and is gaining in popularity in the United States.
How to Plant Kohlrabi
The kohlrabi plant is easy to grow, has few pests or disease problems, and grows pretty quickly in cool weather. There are several different varieties of kohlrabi, but all of them come in either pale green or bright purple, making quite a show in the garden.
Before planting, fertilize your soil with compost or a good organic fertilizer, and then plant your kohlrabi into full sun. When growing from seeds, sow outdoors as soon as the soil can be worked in the spring, when it has reached 45°F (7°C). If you are in a warmer climate, you may want to start your seedlings indoors, and transplant them out 6-8 weeks before the last spring frost.
Kohlrabi strongly prefers cool weather, and will become woody and bitter quickly in the heat. For this reason, many people will often sow kohlrabi into the garden in the late summer, four to six weeks before the first fall frost, so their plants will mature and sweeten in the cold. Kohlrabi are often the longest lasting vegetable in the garden in the fall, and they do very well in cold frames, and even tolerating a nip of snow!
Plant the seeds ¼ to ½ inch deep into the soil, about three to four inches apart, then thin to six to eight inches apart as they grow.
Special Tips for Growing Kohlrabi
Companion Plants for Kohlrabi
Kohlrabi benefits from planting near bush beans, lettuce, beets, onions, potatoes, cucumbers and celery. Do not plant kohlrabi near tomatoes or other cabbage-family crops like kale or broccoli. (Where to get the “Bible” of companion planting)
Plant for Continuous Harvest
You can have a continuous crop if you sow new kohlrabi seeds into the garden every two to three weeks until it gets warm.
Keep Kohlrabi Moist
Drying out is the biggest challenge when growing kohlrabi, because the bulb stems sit upon the ground exposed to the sun. Drip irrigation is highly recommended, but you will also need mulch or compost to keep kohlrabi’s root zone cool, moist and nourished, otherwise you will end up with woody plants that are bitter. Drip irrigation and organic mulch will also prevent the spread of disease through splashing water droplets.
Kohlrabi Pests and Diseases
Kohlrabi is seldom bothered by pests or disease, compared to its cousins cabbage and broccoli, but prevention is always the best measure. Choose varieties of kohlrabi seeds that are resistant to the pests and diseases in your region, and plant kohlrabi in a different spot each year to minimize the risk of contracting or spreading infections.
If your kohlrabi seedlings have been eaten down to the soil, cutworms are usually the culprits. Sprinkle wood ash around the base of the plants to prevent them.
Cabbageworms (the caterpillars of cabbage white butterflies) or flea beetles may bother your kohlrabi plants, but they typically prefer cabbage and broccoli. Use lightweight row covers to keep them off or handpick them.
Aphids can deform kohlrabi leaves, so spray them with a non-toxic, insecticidal soap.
Slugs and snails should be hand-picked with gloved hands and drowned in a pail of water. You can also easily lure them into traps made by placing an inch of beer in a small open container, and sinking it up to its rim in soil or mulch. You can also use copper tape around your garden beds, or diatomaceous earth to keep them away from your plants.
How to Harvest and Store Kohlrabi
Harvest kohlrabi when the stem “bulbs” are no more than 2-3 inches in diameter. This takes between 40 and 60 days, depending on the variety of kohlrabi you are growing. Any bigger than that, and your plants will likely be too tough.
Cut the stems 1 inch below the swollen “bulb.” Remove the leaf stems and leaves, and use the remaining “bulb” in the same way you would broccoli stems or turnips.
Kohlrabi will keep for several weeks in the refrigerator, and for several months in a cold, moist, root cellar.
How to Save Kohlrabi Seed
Kohlrabi belongs to the Brassica oleracea species, which includes broccoli, Brussels sprouts, kale, cabbage, and cauliflower, among others. Because of this, isolation needs to be managed thoughtfully, and crops need to be at least 800 feet away from others in the family to avoid cross-pollination.
Kohlrabi is a biennial, meaning it doesn’t go to seed until its second year of life. So in order to gather seeds, you need to keep some of your plants alive over the winter by either transplanting them somewhere warmer, or using cold frames to protect them from freezing.
After flowering in their second year of growth, mature seed pods become dry and turn brown. It’s important to harvest them at this time, or the seed pods will burst or be eaten by birds and mice.
Seeds can be gathered by cutting entire branches or by harvesting whole plants. Place a tarp or cloth below where you are harvesting, so you can catch any seeds that burst out of the fragile seed pods.
Store kohlrabi seeds in a cool, dark, dry place in an airtight container. Properly stored kohlrabi seeds will remain viable for several years.
How to Use Kohlrabi
There are three traditional ways to make kohlrobi: slaw made by combining grated or julienned kohlrabi with apples; oven-roasted; and blended into a creamy soup. Use your imagination; this tasty vegetable can be roasted, dehydrated, steamed, sauteed, fried, fermented or prepared any way you like to eat cauliflower or turnips.
Unless the bulbs are very young and tender, it’s best to peel them to avoid chewy strings.
Kohlrabi leaves are edible when young and small, but most people find them bitter and tough as they grow larger.
