Kohlrabi

The 'space cabbage': a fast, quirky brassica grown for a crisp, mild swollen stem - harvest it at tennis-ball size, before it turns woody, and succession sow for a steady supply.

Direct sow (or transplant) in cool seasons, thin to 4-6 inches, and succession sow every 2 weeks; grow it fast and even.

Kohlrabi is usually direct sown - it's fast and dislikes root disturbance - but transplants fine if started young. Sow shallowly as soon as spring soil is workable, or 6-10 weeks before first fall frost; the fall crop is crisper and less prone to woodiness. Because it matures so quickly, succession sow a short row every two weeks instead of one big planting, for a rolling supply of tender bulbs.

Thin to 4-6 inches (crowding makes small, misshapen bulbs), give it full sun and rich, well-drained soil, and above all keep it growing without a check. The whole art is steady, even moisture and fast growth - any drought stall or stress makes a fibrous bulb. Row cover over young plants keeps flea beetles and cabbage worms off; established kohlrabi matures so fast it often outruns serious pest and disease pressure.

Even water is everything - it prevents woodiness; feed lightly, keep it growing fast, and watch the bulb size.

Kohlrabi care comes down to one thing: never let it dry out or stall. Even, consistent moisture keeps the swelling stem crisp and mild; a feast-or-famine watering cycle is exactly what makes a bulb woody, fibrous, or split. Mulch to steady the soil, and give a light nitrogen feed to keep growth quick, because fast growth is tender growth.

Watch for aphids on the leaves and cabbage worms chewing the tops, but the plant's speed is its best defense - it's often harvested before pests get established. The most important 'care' task at the end is simply watching the size: once bulbs start swelling they size up fast, so check every couple of days and harvest at 2-3 inches. Waiting for a bigger bulb is the mistake that ruins the crop.

Cut at 2-3 inches (tennis-ball size) while still crisp; oversized standard bulbs turn woody, so harvest on size, not the calendar.

Harvest kohlrabi when the bulb reaches about 2-3 inches across - roughly tennis-ball size - and is still firm and crisp. Slice the stem off at the soil line with a knife, or pull the whole plant. This is a single-bulb crop: each plant makes one swollen stem and doesn't regrow, which is why succession sowing matters for a continuous supply.

The key is to harvest on size, not age. A standard kohlrabi left past 3 inches keeps growing but turns tough, woody, and bitter - so cut them while they're small and tender, even if they look like they could get bigger. (Giant storage varieties like Kossak or Superschmelz are bred to stay tender much larger, up to softball-plus.) Trim the leaves for cooking; peel the bulb's fibrous outer skin before eating.

A few weeks in the crisper; giant storage types keep for months near freezing - and the leaves cook like kale.

Trim the leaves off (they draw moisture from the bulb) and store the bulb unwashed in the crisper, where standard kohlrabi keeps 2-3 weeks staying crisp. The tender leaves keep about a week and cook like kale or collards - use them promptly. Giant storage varieties are the winter keepers: held near freezing at high humidity in a root cellar or spare fridge, they stay firm for months, staying surprisingly tender for their size.

For longer storage, kohlrabi freezes after blanching (peel and cube first, best used cooked), and it pickles and ferments well - crisp kohlrabi rounds are excellent in a quick pickle or a kimchi-style ferment. Its firm, mild flesh takes to these preservation methods far better than watery greens do.

A fast cool-season crop everywhere - spring and fall in the north, fall-through-winter in warm zones.

Zones 3-5: kohlrabi's speed suits short seasons - grow spring and fall crops, and succession sow to fill the cool stretches; the cool summers here keep bulbs crisp. Zones 6-7: classic two-season timing - an early spring crop before heat and a better fall crop, with light frost only improving flavor. Zones 8-9: a fall-through-spring crop; summer heat makes bulbs woody, so skip it. Zones 10-11: a cool-season crop on absolute dates (Sep-March, UF/IFAS pattern). Everywhere the constant is the same: kohlrabi wants steady cool weather and fast growth, so aim for the bulb to size up in cool conditions and it stays tender and sweet; grown into heat, it toughens.

Woody bulbs, splitting, small misshapen bulbs, and no bulb at all are the usual issues - almost all trace to water and timing.

Woody, fibrous, or bitter bulb (the classic failure): either left too long past 2-3 inches, or checked by drought - harvest small, keep moisture even, and grow it fast. Split bulb: uneven water, a heavy soak after a dry spell; mulch and water steadily. Small or misshapen bulbs: crowding (thin to spacing) or a growth stall from cold, drought, or poor soil. Leggy plant, no bulb forming: too much shade, too much heat, or too dense a stand. Bolts to flower without bulbing: a young plant hit prolonged cold (or the crop met summer heat) - don't set out too early, and grow in the cool season. Shot-hole peppering on seedlings: flea beetles; cover young plants.

Low-calorie and remarkably vitamin-C-rich for a crisp crunchy vegetable, plus fiber and potassium.

Kohlrabi is light and refreshing but nutritionally solid: a cup of raw kohlrabi is around 35 calories and delivers a big dose of vitamin C - more than an equal weight of many citrus fruits - plus good fiber, potassium, vitamin B6, and the glucosinolate compounds shared across the brassica family. Purple varieties carry a little anthocyanin in the skin, though the crisp flesh inside stays pale in every type.

Because it's so often eaten raw, kohlrabi delivers its heat-sensitive vitamin C intact - a real advantage over brassicas that are always cooked. Don't overlook the leaves: they're as nutrient-dense as kale (high in vitamins A, C, and K and calcium), so cooking the tops rather than composting them adds a second, greener serving from the same plant.

Best raw and crisp - peeled into slaw and sticks - but also great roasted, sautéed, or in soups; cook the leaves like kale.

Kohlrabi shines raw. Peel off the fibrous skin and the crisp, juicy flesh - mild, sweet, faintly like a broccoli stem or a peppery apple - is perfect grated into slaw, cut into sticks for dip, sliced thin into salads, or matchsticked into a fresh remoulade. It's the treatment that best shows off its texture, and it's how much of Central Europe and India eats it.

Cooked, it's just as good and holds its shape: roast peeled wedges until caramelized, sauté cubes with butter, add it to stir-fries and curries, or simmer it into a silky soup or purée. The tender leaves cook exactly like kale or collards - sauté or braise them - so a kohlrabi plant is really two vegetables. Purple types look striking but taste the same as green; always peel before eating, raw or cooked.

Biennial and cross-prone like all Brassica oleracea - saving true seed needs isolation, so beginners buy kohlrabi seed.

Kohlrabi is a biennial Brassica oleracea, the same species as cabbage, broccoli, kale, collard, and cauliflower - which means it crosses freely with all of them. To save true seed you must overwinter a plant into a second year to flower, and isolate it from every other brassica in bloom by 800+ feet (or cage and hand-pollinate), or the seed won't come true. On top of that, the edible bulb is the plant's stem, so a seed plant is one you don't eat.

The practical guidance for beginners is simple: buy kohlrabi seed. It's inexpensive and reliable, and many varieties (the Vienna types) are open-pollinated, so the varieties are stable if isolation is handled. If you want the challenge, overwinter one healthy plant, let it bolt and flower alone, dry the pods on the plant, and thresh out the seed - a single plant yields plenty for years of sowing.

No meaningful herbal tradition - kohlrabi's value is dietary, as a crisp, raw, vitamin-C-rich brassica.

Kohlrabi has essentially no folk-medicine history of its own; it's a relatively modern selection of wild cabbage, valued at the table rather than in the medicine chest. Its health contribution is straightforwardly dietary and shared with the brassica family: vitamin C, fiber, and glucosinolate compounds studied for antioxidant activity as part of a diet rich in cruciferous vegetables. Being eaten raw so often, it delivers its vitamin C especially well.

The honest framing is that kohlrabi is excellent, refreshing food, not a remedy. Like other brassicas it contains raw goitrogens that only matter in extreme quantities with iodine deficiency - a non-issue for normal eating - and its leaves, like kale's, are high in vitamin K, worth keeping steady for anyone on blood-thinning medication. There's nothing to over-claim; just eat and enjoy it.

A relatively young European creation from wild cabbage - swollen-stem selection perfected in Germany and Central Europe, now spread worldwide.

Kohlrabi is one of the more recent branches of the ancient wild cabbage Brassica oleracea - developed by selecting for a swollen, edible stem rather than leaves or buds. It appears in the European record around the 1500s and became a staple of German and Central and Eastern European gardens, where its name (Kohl, cabbage + Rabi, turnip) was coined and where it's still eaten with real affection.

From there it spread east and west: it's beloved in India (where it's called ganth gobi and cooked into curries), across Central Europe, and in Vietnamese and other Asian kitchens. In the English-speaking world it long stayed a curiosity - the odd-looking 'space cabbage' - but its speed, cold tolerance, and versatility have steadily won it a wider following among home gardeners rediscovering an easy, quick, and unusual crop.