Growing kohlrabi in your garden can be an easy and rewarding experience. But, there are a few things you need to know before you get started.

What is Kohlrabi?

The kohlrabi plant, Brassica oleracea var. gongylodes, is a cruciferous biennial vegetable in the family Brassicaceae, which is grown for its thick root, which resembles a turnip and is often eaten raw or cooked. The kohlrabi plant grows from a stout taproot and develops a large bulbous root and a broad stem with oval or rounded leaves. The leaves are broad and lance-shaped with a bluish color and are edible. 

It got its name from the German words Kohl, which means cabbage, and Rabi, which means turnip, which well describes its taste after cooking. It is often called German turnip or German cabbage in English spoken territory.

Kohlrabi is a very nutritious, tasty vegetable that is more resistant to drought than other cabbages and thrives in areas where other cabbage family members growing is not possible.

Kohlrabi varieties

There are many different varieties among them. Most types develop around thickened stems than the stem, but some may have a flatter stem. Also, the head of a kohlrabi can be purple or light green, and in some varieties can be white or blue, so the types of this plant differ accordingly. It is possible to distinguish early and late varieties, depending on when they ripen.

Early varieties mature in about 10-15 weeks, and late varieties in 15-20 weeks. In addition to size, color, ripening speed, taste, and shape, you can select types with better storage characteristics when choosing a variety for planting.

Several most famous varieties are Blue Vienna, White Vienna, Purple Vienna, Grand Duke, and Gigante. 

kohlrabi varieties green purple

Why should you grow kohlrabi in your garden?

Kohlrabi is a quick-growing crop that requires little maintenance once it’s established. It’s a cool-season vegetable that grows best in spring and or fall. Kohlrabi can be stored for several weeks or months, making it a great fall crop. This vegetable is also one of the most nutritious and has more than a few health benefits. Its nutritional value is comparable to cabbage and cauliflower.

According to NutritionData, It’s rich in vitamin C, potassium, and dietary fiber. It has a great manganese, copper, magnesium, and phosphorus source. Kohlrabi can be a delicious, healthy snack, low-calorie veggie but still a great source of nutrients. It may help lower cholesterol, prevent cancer, and fight obesity, among other benefits. German turnip is also packed with antioxidants and carbohydrates.

Kohlrabi’s mild flavor makes it an easy and tasty vegetable to eat. You don’t have to worry about getting bored with it. It’s an affordable, healthy, and versatile crop for the entire year.

How to grow kohlrabi?

Kohlrabi is a vegetable that grows fast and does not require much care. It has an edible stem that tastes like a cross between a turnip and a cabbage. The plant can grow well in many soils and are relatively free of pests and diseases.

The seeds should be sown early in spring when it comes to planting. If you plant them too late when it is warm, you may encounter problems such as poor germination. When you plant kohlrabi seeds, it is good to add some compost to your soil to improve its quality. Kohlrabi requires plenty of space to grow and will produce better in full sun than in partial shade.

When to plant?

Kohlrabi grows quickly and can be planted year-round in many parts of the country but prefer cooler temperatures around 60 F. It is most productive when sown in the spring but if you live in warmer regions start them in fall.
For early spring planting, start your seeds indoors, in individual cell trays, containers, or pots, about 3 to 4 weeks before the last spring frost. 
For fall planting and winter harvesting in warm regions, start seeding in late summer.

german turnip seedlings planting kohlrabi

Sow seeds

Kohlrabi can be direct-seeded in your garden ground or started indoors for transplants. You can sow seed in the peat pots, planting them 0.25 inches deep. The seeds will germinate in 3 to 10 days.

Once they sprout and have 3 to 4 leaves, you can transplant them in garden beds, containers, or directly in the ground to about 1 foot apart.

If you’re starting by direct seeding outdoors, you can plant them once the soil temperature reaches 50°F. Plant 1 seed every 2 inches, and when they reach 3 to 4 inches tall and or they have 3 or 4 true leaves, thin them to 6 to 8 inches.

It is essential to water seedlings thoroughly after transplantation.

Soil and watering

Kohlrabi grows best in fertile, well-drained soil with a pH between 6.2 and 6.8. and a temperature of around 50 degrees Fahrenheit will ensure the best yield. When preparing the soil for planting, you can improve the soil’s nutrition by adding compost or other organic matter to the ground. It can be compost soil or aged manure.

Water your kohlrabi regularly. Water it just deep enough so that the roots are moist but not soaking wet. Keep the soil moist but not soggy, and don’t let the ground get too cold. German turnip is most susceptible to rot when it is overwatered. It requires only 1 to 1.5 inches of water a week.

An even water supply is essential for proper growth. The thickened stem can crack after a dry period when heavy rainfalls.

transplanting kohlrabi seedlings in garden

Fertilizing

Kohlrabi is a hardy crop and requires minimal fertilizer. But if you want to grow large heads of German turnip, you’ll need some phosphorus, sulfur, and nitrogen. The most common organic fertilizer for kohlrabi is a bone meal and chicken manure. The nitrogen helps to stimulate root growth and produce more giant heads.

In addition, kohlrabi plants are deep-rooted and thus require a more considerable amount of nitrogen than many other crops, so additional nitrogen is needed to promote vigorous root growth. If you have clay soil, mix a tablespoon of ground eggshells with 1 gallon of water and spray it around the plants. The calcium will help the soil hold onto the nutrients. You can also use blood and bone.

Companion plants

Kohlrabi, a root vegetable, is a member of the cabbage family. As such, it is very susceptible to the same bugs that affect members of the cabbage family. Some of the best companion plants for kohlrabi are onions, garlic, and radishes will help to prevent pests. Beets, shallow, and potatoes will help loosen the soil. Same family members like kale, broccoli, and Brussels sprouts are also good companions.

Avoid planting kohlrabi alongside tomatoes, peppers, cole beans, pumpkins, sunflowers, and strawberries. These plants compete for space and nutrients, resulting in poor growth for all.

Propagation

Kohlrabi is a biennial vegetable that will flower in the second year of growth. The plant can also bolt during the first year if it experiences hot temperatures during the summer.

You can leave the plant in the ground to overwinter if you live in areas with mild winters.

The plant can’t survive brutal winters with temperatures of -7 Celsius, so to collect seeds from previous season kohlrabi plants, you need to store heads during the winter correctly. To do that:

  1. Harvest them by gently pulling them out with roots.
  2. Remove the side leaves but leave 2 to 3 central ones.
  3. Place them in a bucket, protect the roots with sand, and keep them in a dark space.
  4. Wait for the spring and then transplant them outside.

Kohlrabi will start to bolt during the late spring, and there will be a few yellow flowers on the main stem. The plant will send energy to develop the seeds inside the pod as the flowers mature.

The pods will get hard and woody during the summer, and you can collect their seeds when they are fully ripe. The seeds will be brown 1 to 2 mm in size and should be kept in a dry and cool place.

When to harvest?

Kohlrabi is ready to harvest when the stems are firm, 2 to 3 inches in diameter, and you can easily pull them out of the soil.
The plant will reach maturity in 50 to 70 days, but some varieties take longer.Cut the stems with a sharp knife just under the heads. Remove the roots from the ground, and put them in compost.
If we cut off only two-thirds of the head in the summer so that a few leaves remain on the remaining part of the plant, small kohlrabis will grow in the axils of these leaves during the summer to achieve a double yield.

kohlrabi ready for harvest

Common problems

Kohlrabi growing problems can be related to poor soil, low light levels, or water conditions. They can also be affected by a range of diseases which are mostly fungus related, and you can avoid most of them by rotating new plants every year with crop rotation plan.

  • Downey mildew
  • powdery mildew
  • damping-off
  • clubroot
  • Alternaria leaf spot

According to the PlantVillage, the most common pest problems are:

green kohlrabi ready for harvesting

Conclusion

Kohlrabi is a root vegetable that grows quickly in almost any soil type. It’s a fast-growing vegetable that can be harvested at any time of year. German turnip is high in fiber, low in calories, and has many health benefits. In addition to being a good source of vitamins, minerals, fiber, and carbohydrates, it also helps boost energy levels, protect you from free radical levels and improve overall metabolism. The best part is that it’s delicious, and you can eat the stems and leaves raw, sauteed, roasted, or even boiled. We love this root vegetable for its versatility and how quickly it grows. 

Frequently asked questions

Why is my Kohlrabi not Bulbing?

Kohlrabi is a root vegetable that resembles a turnip. If your plant is not bulbing, it is most likely because it does not have enough space to grow. It would be best to plant them 1 foot apart from each other or half a foot from the edge of the pot, container, or garden bed.
Other reasons for not forming bulbs are poor soil and too high air temperatures causing the plant to trigger bolting and sending nutrients into flowers and seed pods.

young kohlrabi purple variant

How to Tell if Kohlrabi is Bad?

It is probably bad if your plant is discolored and has dark brown foliage and wilts. 
The kohlrabi stem should be firm, not softy and squishy. If they are moldy, smelly, and starting to show any bacterial formation throw them away immediately cause it is dangerous for eating and further growing with other plants. Watch out for brown and moist spots cause it is signs of rot.
If you leave kohlrabi in-ground for too long, they tend to become woody; that doesn’t mean they are bad but harvest them on time for the best flavor.

How to Store Kohlrabi?

After harvesting, we pack kohlrabi in slats or boxes with thickened stems along the shorter sides and leaves in the middle.

Autumn harvest packaging is done without leaves in slats or mesh bags. Plants packed with leaves may only be stored for 2 to 3 weeks at a temperature of 0 to 1 ° C, at a relative humidity of 97%.

Autumn kohlrabi, usually packed without leaves, can be stored in dark and relatively cold places like cellars or basements for several months. 

According to Michigan University, canning is not recommended, but you can keep stems in the refrigerator for several weeks or freeze them for longer preservation.

purple kohlrabi harvested ready for storage