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  1. Kohlrabi is a member of the brassica family. What looks like a root is actually a thickened stem. The leaves are also edible.
  2. Kohlrabi is a fairly easy vegetable to grow on the prairies but since it is related to canola, is also prone to a number of insect problems. Row covers are recommended to keep pests at bay. 
  3. Kohlrabi can be direct seeded into the garden in early spring, but there is a benefit to transplanting seedlings. Transplants will produce earlier than direct seeded plants if you live in the prairies. Using transplants is a must for the far north.
  4. If you direct seed kohlrabi, hold off thinning until mid-June. Because of the intense insect pressure on brassicas in the prairies, some of the plants will be lost to insect damage, unless row covers are used.
  5. Kohlrabi is also available in a purple cultivar.

Kohlrabi are classified as brassica vegetables (cole crops) and belong to the mustard family of plants. These Brassicaceae plants were formerly classified as cruciferous plants.  ‘Cruciferous’ because the petals of the flowers of these crops form a cross. 

Brassica vegetables include cabbage, broccoli, cauliflower, kale, kohlrabi, Brussels sprouts, radish, turnip, rutabaga, Chinese cabbage, mustard greens and mustard cabbage (bok choi or pak choi). Since all of these plants share a recent common ancestor, they all have very similar growing recommendations and problems.

While they are quite similar, there are some key differences to ensure best success so we've broken these into separate articles for easier instruction.

Kohlrabi is high in vitamins C and B6, folate, potassium and fibre. Check here for detailed information from the USDA National Nutrient Database for Standard Reference. Harvard School of Public Health recommends eating them no more than once a week.

The Canadian Food Guide recommends that roughly half of the food on your plate should be fruits and vegetables.

Canada Food Guide: What's On Your Plate?

Growing outdoors

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Brassicas grow best in well-draining, moist soil. You can improve your soil's ability to hold moisture by adding organic matter such as compost or aged, composted manure. Do not use fresh manure as a soil additive. If you think your soil needs remediation, see our Soils and soilless mixes page for detailed advice.

As a leafy vegetable not grown for fruit or flower, they do not require full sun to produce well and can tolerate some light shade. However, they will not be successful in very shady areas.

Kohlrabi are best grown outdoors in the ground, be it in raised beds or unraised/ground level gardens if the soil is suitable. They are not typically suitable for most container, hydroponic, straw bale, or other alternative growing methods.

Kohlrabi grows to maturity between 38 to 55 days. They can be direct seeded, but may also be grown as transplants for an earlier start in the garden. Transplants can be grown in your own home or purchased from a local greenhouse.

Starting your own kohlrabi plants from seed

  • Start transplants about 5 -6 weeks prior to transplanting out. You can transplant seedlings as soon as daytime temperatures reach 10°C and night temperatures are not below -2°C for several nights in a row. In Saskatoon, your plant out date is around May 13 so you can start your transplants around the first week of April.
  • Sow seeds 0.5 cm deep in a commercial soilless media containing peat moss or coir, perlite and vermiculite.  Soilless media provides a disease-free environment as well as excellent drainage to minimize root disease problems. Seed 2 - 3 seeds per pot and then thin to the strongest plant after they have grown their first set of true leaves. 
  • Use flats, pots or containers with bottom drainage holes. At a soil or media temperature of 24°C, brassica seeds will germinate in 5 or 6 days.
  • Good lighting is crucial for the growth of healthy seedlings. Brassica seedling transplants require a minimum of 14 hours of light each day.
  • Leave a fan blowing on your young seedlings as they grow to will help to grow heartier plants and to reduce some seedling diseases.
  • For more details, check out our article on growing your own transplants.

The ideal brassica transplant:

  • is approximately 10-15 cm tall.
  • is dark green in color, though the lowest leaves may be a lighter color.
  • has a good root system but is not root-bound (tight, hard ball of roots that do not break apart when gently massaged). 
  • has a stem that is strong and sturdy. The internodes (spaces between leaves along the stem) will be small.  Transplants that are too tall will tend to break and dry out more easily once planted out into the garden. Research has shown that stem diameter can be increased and height controlled by providing seedlings with constant air movement from an oscillating fan – or by lightly brushing seedling tops with a tea towel or stick at least 20 times daily.

Fertilizing recently planted seeds or young seedlings is not recommended. The first leaves that grow are not true leaves. They are "seed leaves" called cotyledons and are shaped like a capital B. All leaves that grow after these are true leaves. Once your seedling is mature enough to grow true leaves, you can begin to fertilize two times per week using 20-20-20 water-soluble fertilizer. Mix according to label directions.

Harden off transplants prior to planting out by moving them outdoors into a sheltered, frost-free location at least 3 days prior to transplanting.

Don't forget to label what you planted. It's also helpful to draw a map to help you track planting locations and success each year. This information is critical if you're rotating your crops to help prevent insect and disease issues.

Brassicas tend to attract kohlrabi moths and flea beetles. If you're planning to stay pesticide-free, it's important to use row covers to prevent insect damage. This is especially critical if you're located near canola fields. Row covers should be installed very soon after planting, long before the insects arrive.

If you have had cutworm problems in your garden, place a collar around your transplants right after planting. Make collars out of toilet paper rolls, or any tin can or plastic container such as a yogurt container with both ends removed. Insert the collar at least 5 cm in the ground to prevent cutworms from feeding on the stems of your transplants.

Timing

  • Kohlrabi may be direct seeded in the garden or planted as transplants. See our transplants tab for tips on growing or purchasing your own transplants.
  • If direct seeding, try Succession planting as kohlrabi only needs between 38 to 55 days to maturity. Since kohlrabi is best harvested young, you can get several crops of kohlrabi in one growing season.
  • To direct seed, plant seeds 1 cm (½") deep and 3 cm (about 1") apart in rows 30 cm (12") apart. Thin to about 15 cm (6") spacings.
  • You can transplant kohlrabi seedlings as soon as daytime temperatures reach 10°C and night temperatures are not below -2°C for several nights in a row. In Saskatoon, your plant out date is usually any time after May 13. If temperatures are too cold, kohlrabi may bolt (send up a flower stalk).
  • Transplants must be hardened off before transplanting outdoors. While mature brassicas are frost tolerant, young transplants are less so.

Planting instructions

  • When planting, cover the entire transplant “plug” or seed ball with soil to prevent the plant from drying out.  Exposed peat or coir within the plug will act as a wick, drawing water away from the transplant and drying out the root ball.
  • Gently massage the roots within the plug so that the roots will grow into the surrounding soil and not remain restricted within the ball.
  • Kohlrabi transplants should be spaced 15 cm apart within the row, allowing 30 cm between rows.
Here are cultivar recommendations from the North Dakota State University Cultivar Trials, as they share a similar prairie climate and soils. You may download their list here: North Dakota State University Vegetable Cultivar Recommendations for 2021
    • Early White Vienna, Kolibri, Kossak, Winner

The following cultivars are recommendations from the University of Saskatchewan vegetable program field trials which were conducted from 1989 through 2016. Although this information is no longer current, some may find it useful.

  • Early White Vienna, Express Forcer, Kompliment, Kongo, Korist, Rapid Star, Winner, White Vienna

  • Actively growing kohlrabi plants prefer 2.5cm moisture/week in well-drained soils.
  • Kohlrabi can be grown successfully most years without additional water though you can expect smaller plants as a result. Water will affect yields, so if you're using more intensive growing methods you will need to water.
  • Pick weeds as they appear, especially those in the Brassicaceae family which attract the same insects: common pepper-grass, shepherd's purse, stinkweed, Argentine canola, ball mustard, dog mustard, flixweed, Polish canola, wild mustard and wild radish. 
  • To reduce weeding, apply a thick layer of mulch around your kohlrabi plants.

Kohlrabi is not suited to fall seeding.

Kohlrabi are best grown as transplants in the far north.

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Forgot what you planted? Not sure if it's a weed? Germination in broccoli

See our preservation section for more videos.

Growing in containers

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Kohlrabi could be grown in a container outdoors. Choose a large container - at least 8 liters (2 gallons) or larger. 

Smaller or leafy brassicas such as kale, bok choi, radishes or pak choi work very well instead.

Early White Vienna

Saving seeds

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Seeds are expected to be shelf-stable for one year from date of sale if purchased from a reputable retailer. If you wish to save your seeds beyond that, you should store them in the fridge in a jar. Seeds lose viability quickly if they dry out too much or get too warm.

The life expectancy of kohlrabi seed stored under favourable conditions is about four years.

Seeds stored under less favourable conditions will show poor germination after just a single year of storage. Beyond this, you can expect your germination rates to go down (ie. not all of your seeds will grow, but some might). To test your seeds, you can do a simple germination test. Follow the link for instructions. If you are still getting some seeds germinating, seed more thickly and thin any extra.

Kohlrabi are biennials and set seed in their second year of growth when grown in a warmer climate. Since they do not survive a prairie winter, seed saving is not recommended. 

As our climate continues to change, this may become a viable option for prairie gardeners in the future.

Harvest

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Check your seed package for days to maturity. 

Kohlrabi should be harvested young when the swollen stems are about 5 - 8 cm (2" - 3") in diameter. Over-mature kohlrabi become woody in texture and lose some of their flavour. 

The leaves can be harvested anytime. 

 

Loosen the soil around the kohlrabi with a fork (take care not to bruise or damage it) and pull the entire plant from the ground. Remove the leaves and trim the roots from the swollen stem.

Kohlrabi doesn't have a particularly high respiration rate. While it is important to keep them cool during harvest, as it is with most vegetables, it isn't critical.

Storage

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Kohlrabi can be stored in the refrigerator for a few weeks to a month (see below for details). If you're hoping to store them longer than a month, you will need to use other preservation methods such as freezing, fermentingcanning or drying.

  • The ideal storage conditions for kohlrabi is just above 0˚C with high humidity. Your fridge is likely a few degrees warmer than this, but it will work as long as you manage the humidity.
  • To maintain adequate but not excessive humidity either poke a few holes in your bag (ok), or use a plastic bag meant for vegetables (better), or keep a few sheets of paper towel in the bag with them and switch the paper towels for new ones once they become too moist (best).
  • For detailed advice on other potential spaces or methods, see our cold storage page.

Cooking and preserving

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Kohlrabi should be trimmed and peeled - the inner part is crisp and fresh tasting. Try shredding it and adding to a salad or in your favourite coleslaw recipe. Kohlrabi can be roasted, grilled or steamed as a side dish, or added to soups and stews. 

The leaves are nice sauteed or added to a stir fry. 

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Dehydrating Cabbage

Alternative ways to eat common vegetables

 

Troubleshooting

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Kohrabi plants are relatively low maintenance. Providing their water, light and soil needs are managed they don't tend to get a lot of issues.

Ensuring that you maintain healthy soil with adequate organic matter and use row covers to prevent insect problems will go a long way towards preventing most issues.

 

See the Common problems tab on this page for advice on other specific kohrabi issues.

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Common questions

While it's tempting to grow plants as large as possible, kohlrabi does become tough and stringy if it overmatures. The best kohlrabi is when it is about 5 - 8 cm (2" - 3") in diameter.

Check your seed package or transplant tag for the correct mature size. There are some kohlrabi that are bred to be larger. 

Kohlrabi stems should be round and thick. 

Thin stems may be a result of plants spaced too close together. Sometimes weather plays a role: too much heat or freezing temperatures, or too little water.