Growing Kohlrabi

Updated: Sep 15

Otherwise known as German turnip, this uniquely shaped vegetable can be enjoyed both raw and cooked. It’s got a fairly mild flavor, somewhere in between cabbage and turnip. Because of its crunchy texture, it’s a great addition to many dishes – from soups to salads to slaws.

To help ensure your Kohlrabi thrives, I’ve put together this how to grow Kohlrabi video and transcript that walks you through:

  • Varieties of Kohlrabi available

  • Starting & caring for Kohlrabi at all stages

  • Fertilizer and/or Mulching

  • Transplanting best practices

  • Kohlrabi Companion Plants

  • Pests, Diseases and what to do about them

  • Harvesting and storing your Kohlrabi


Listen to this Article:



Glossary of kohlrabi terms

Growing Kohlrabi is easier when you know the terms you'll see floating around, so lest start there. :)


THINNING

The process of gently removing seedlings at a certain growth stage to leave only the strongest and most mature plants behind.

This encourages your plant to grow properly, and allows kohlrabi to thrive without any major competition.


TRUE LEAVES

The first leaves that look like those of a mature kohlrabi plant. These true leaves are more firm, and have sharper edges as compared to the rounder and softer seedling leaves.


HARDENING-OFF

The process of getting seedlings used to outside conditions. By exposing your transplants to wind, sun and outside temperature every day for a few hours, it toughens them up and prepares them to survive outside.


ANNUALLY GROWN

Plants that mature in one growing season and can be harvested at its end. In the case of kohlrabi, in grows fully within 40-60 days.

Close up of a Pile of Kohlrabi

Varieties of kohlrabi

Growing Kohlrabi comes in different colors and sizes, so lets pick one that's right for your vegetable garden...and dinner plate.


EARLY PURPLE VIENNA

Kohlrabi: Early Purple Vienna Variety

This variety has purplish leaves and bulbs with a mild turnip/ cabbage flavor. It takes about 60 days to reach maturity.



EARLY WHITE VIENNA

Kohlrabi: Early White Vienna Variety

Its round, light-green bulbs have a creamy and tender white flesh. This variety is quite heat tolerant and matures in 55 days.




GRAND DUKE

Kohlrabi: Grad Duke Variety

This one is the most disease-resistant compared to other varieties, and its pale green crisp bulbs are also the largest. It takes 45-50 days to become harvest-ready.



KOLIBRI


Kohlrabi: Kolibri Variety

This variety has smooth bright purple skin with crisp white flesh inside. Its texture is similar to a crisp apple, and has mild brassica flavors. It takes about 55 days to mature.




Starting your kohlrabi seeds

Steps for growing Kohlrabi when starting with their little seeds.

  • When growing your kohlrabi, your soil should have a pH of 6.0-6.8. Also, this crop prefers soil temperatures between 45-85°F for germination.

STEP 1

  • Plant your seeds a quarter to a half inch deep, keeping them spaced about 6 inches (15.2cm) apart in rows that are about 2 feet (61cm) apart.

STEP 2

  • Once your seedlings have 3-4 true leaves, thin them to be 12 inches (30 cm) apart.

STEP 3

  • When started indoors, your seedlings will be ready for transplant after 5-6 weeks - once they have 4-6 true leaves.

  • If there’s any cracking, it usually means your soil moisture isn’t great – so make sure to water your kohlrabi frequently - about 1-2 inches of water each week.

Kohlrabi Harvested and on the Counter

Caring for kohlrabi

Growing Kohlrabi each step of the way.

  • I’ll tell you everything you need to know about watering, fertilizing, and mulching kohlrabi, plus transplanting best practices and your growing structure options.

  • I’ll also let you know what does and doesn’t grow well with this crop.

  • Kohlrabi can be grown in USDA zones 3 through 10, and it prefers a soil pH of 6.0 to 6.8. Though it can adapt well to heavy soils, it struggles with sandy soils. It’s a heavy feeder, too.

  • High summer temperatures will reduce its growth and decrease its quality. So, kohlrabi grows best when temperatures stay under 75°F.

  • Ideally, the right time to grow this crop is in the spring or fall, to avoid the heat of summer. Also, it thrives best in full sun, but will also tolerate some light shade.

  • When it comes to water, kohlrabi needs about 1-2 inches (2.5-5cm) per week. It’s super important to water it frequently so that its shallow root system has a steady supply.

  • You’ll want to avoid watering from above as much as possible, though. Wet leaves that don’t have enough time to dry up during the day will become more prone to diseases.


FERTILIZING AND MULCHING

Growing Kohlrabi with the right plant food and protection.

  • Apply 4-6 cups of an all-purpose fertilizer (16-16-8 or 10-10-10 will work) per 100 square feet before you plant. Use another 1 cup per 10 feet (3m) of row using a nitrogen-based fertilizer (21- 0-0) about 3 weeks after planting.

  • You can also work 2-4 cups of some well-composted organic matter into your soil before planting to enrich it with nutrients.

  • Apply mulch (grass clippings, straw or wood chips) when your plants are about 5 inches tall, which will help to contain moisture keep weeds from growing.

  • Weeds compete with kohlrabi for water, light and nutrients – so you definitely want to keep them under control.

Kohlrabi Leaves

TRANSPLANTING BEST PRACTICES

Growing Kohlrabi if you're bringing transplants into the gardn.

  • Make sure to first harden-off your kohlrabi plants before transplanting them outdoors. To do so, you’ll want to lower their water intake and temperature, then expose them to outside conditions for a few hours each day.

  • This will toughen up your plants, preparing them to thrive in their new outdoor conditions.


GROWING STRUCTURE OPTIONS

Growing Kohlrabi is easy in most spaces. Below are the most common ones used in horticulture for self sufficiency.


CONTAINERS

  • Definitely a great option, but they have to be big enough to accommodate the whole plant. They’ll also need holes in the bottom to make sure your soil gets good water drainage.


OPEN FIELD

  • Planting in an open field will give your kohlrabi the most space to grow. But before you do, check your soil for its fertilizer needs and possible disease infection.

  • Also, when growing in an open field, you usually don’t have to water your plants as regularly as you would container- raised plants.


RAISED BEDS

  • These are a great option to improve your soil’s drainage while also getting a higher soil temperature.

  • This will prevent the spread of certain diseases that favor cool and/or moist conditions. Another bonus is that you won’t have to disturb your soil or plants as you work.


Kohlrabi Companion Plants

Growing Kohlrabi with plant friends that protect them


Best companion plants for Kohlrabi

  • Bush beans fix nitrogen in the ground, which is a good thing for your kohlrabi. Beets, celery, cucumbers, lettuce, and onion are also great companion plants.

Avoid growing Kohlrabi next to

  • Potatoes, tomatoes, eggplants and peppers all have different soil requirements, so they don’t make good kohlrabi companions.

Freshly Harvested Kohlrabi

Common challenges and their solutions

  • There are a few issues, pests, and diseases that could potentially harm your kohlrabi plant. Not to worry – I’ve listed them below, plus how you can either avoid or fix the problem.


COMMON ISSUES

TOUGH AND WOODY PLANTS

  • Kohlrabi plants should be harvested when they’re 2-3 inches (5-7cm) in diameter. If they continue to grow, they’ll become much woodier in flavor.


CRACKING

  • This typically means that your soil moisture is not ideal – so make sure that you’re watering your kohlrabi frequently.

  • In general, they need about 1-2 inches of water each week.


POTENTIAL PESTS

Growing Kohlrabi pest free with these solutions


CABBAGE LOOPER

These caterpillars are light to dark green, and chew holes in the leaves where they also hide.

  • Solution: Apply insecticidal soaps and hand-pick the caterpillars when you spot them.


APHIDS

These insects have soft bodies that are green or black. They feed on the undersides of leaves, causing them to become crinkled and curled, and they also spread diseases.

  • Solution: Either use a strong water stream to wash off the aphids, or apply insecticidal soaps.

  • Make sure to also inspect your transplants for an existing infestation before planting them.

  • Keep in mind that these aphids aren’t very mobile, so it’s not uncommon to find one heavily affected plant surrounded by ones that are fine. Simply remove and destroy the infected plant.


DIAMONDBACK MOTH

You can find these caterpillars on the undersides of your plant’s leaves. They tend to spread on the leaves, snacking on them and causing little holes to appear.

  • Solution: Natural enemies like wasps and other predators usually keep them in check.


FLEA BEETLE

Small black beetles that feed on seedlings and jump when disturbed. They can stunt your plants’ growth, and might even kill your seedlings.

  • Solution: Placing yellow sticky cards between your plants can help you tell how heavy the infestation is.

  • Be sure to also give your kohlrabi plenty of water and nutrients to keep them strong, which helps them to deal with an infestation much better. You can also use insecticidal soaps.

Kohlrabi Plant Picked and on the Counter

POTENTIAL DISEASES

Growing Kohlrabi disease free with the following tips


DOWNY MILDEW

This fungus thrives in cool and moist conditions, causing yellow patches to form on leaves.

  • Solution: Practice good crop rotation, ensure good air circulation, and water your plants early in the morning.

  • This last tip gives your plants enough time to dry out during the day, making them less vulnerable to infection.

  • Also, if you have any infected plants, be sure to remove all crop remains after harvest to avoid re-infection (since this fungus can survive in crop residue).


BLACK ROT

This disease causes V-shaped lesions on leaves, eventually making them wilt. This disease can happen at any stage of the growth process, and can be spread by splashing water, equipment, wind, people or insects. Its symptoms are also quite similar to those of overwatering, drought stress, or too much fertilizer.

  • Solution: Space out your plants properly to avoid wet leaves, and also to improve air circulation.

  • Be sure to remove and destroy any infected plants, practice good crop rotation, and avoid overhead watering.


BLACK LEG

Little lesions will appear along the stem that eventually grow bigger, turn brown with a black border, and become sunken – and they might even attack the roots of your plant. This disease can affect plants at any stage of their growth, from seedling to maturity.

  • Solution: Practice proper crop rotation and avoid working in your garden when it’s wet. Also, it’s important to improve your soil’s drainage as well as the amount of air circulation around your plants.

  • After harvest, be sure to also destroy any remains of your infected crops.

ALTERNARIA LEAF SPOT

This disease causes dark brown to black circles that look like targets, and these lesions can dry and fall out. Generally, plants can tolerate this fungus since it’s mainly cosmetic, but it can act as a gateway for more diseases. Also, heavy infections may cause a decrease in your crop yields.

  • Solution: Practice good crop rotation, avoid overhead watering, and be sure to space your plants out enough so that they can dry faster.

  • Spacing will also improve air circulation, which is helpful since this fungus favors warm and moist conditions.

Kohlrabi Harvested and Ready to Cook

Harvesting and Storing

Growing Kohlrabi for your plate and pantry!

  • Harvest your kohlrabi once its swollen bottom is 2-3 inches in diameter. Simply cut the bulb/ stem directly above your soil line, and then separate the bulb from its roots.

  • In general, kohlrabi can be stored at 32°F for 2-3 weeks. When preparing it to eat, simply peel the outer layer to reach the crisp flesh inside.


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