Harvesting Kohlrabi Plants: How And When To Pick Kohlrabi

Harvesting Kohlrabi Plants: How And When To Pick Kohlrabi

By: Susan Patterson, Master Gardener

While kohlrabi is normally considered a less traditional vegetable in the garden, many people grow kohlrabi and enjoy the pleasing flavor. If you’re new to growing this crop, then you’ll likely find yourself seeking information about harvesting kohlrabi plants. When you want to know when to pick kohlrabi, it helps to learn more about the growing conditions of the plant.

Kohlrabi History and Appearance

Kohlrabi is in the same family as mustard and close relatives with cabbage, cauliflower, broccoli, kale and Brussels sprouts. The plant was grown first in Europe around 1500 and came to America 300 years later. It produces a swollen stem that has a broccoli or turnip type flavor and can be steamed or eaten fresh. Many people have questions about growing, caring for, and when to pick kohlrabi in the garden.

Growing Kohlrabi

Grow kohlrabi in a sunny location with rich, well-drained soil. Before planting, work at least 3 inches (7.6 cm.) of organic matter into the soil. Kohlrabi can be grown from seeds or transplants. Seeds should be planted ¼ – ¾ inch (.6 – 1.9 cm.) deep around one to two weeks before the last spring frost. Thin seedlings when plants grow at least three true leaves. Leave 6 inches (15 cm.) between each plant and 1 foot (30 cm.) between rows.

Planting every two to three weeks ensures a continuous harvest from spring through early summer. For a jump on the season, you can plant kohlrabi in a greenhouse and transplant as soon as the soil can be worked. Provide regular water, mulch for moisture retention and be sure to keep weeds to a minimal for best results.

How Long to Wait for Kohlrabi Harvest

You are probably wondering how long to wait for kohlrabi harvest. Fast growing kohlrabi grows best in temperatures 60 to 80 F. (16-27 C.) and is ready to harvest in 50 to 70 days, or when the stem reaches 3 inches in diameter.

Harvesting kohlrabi plants is best done when they are small. This is when the vegetable’s flavor will be the best. Kohlrabi left in the garden for a long time will become extremely tough and unpleasant tasting.

How to Harvest Kohlrabi

In addition to knowing when to pick kohlrabi, you need to know how to harvest kohlrabi plants. When harvesting kohlrabi, it’s vital to keep an eye on the swelling base. Once the stem reaches 3 inches (7.6 cm.) in diameter, cut the bulb form the root with a sharp knife. Position your knife at soil level, just under the bulb.

Pull the leaves off of the upper stems and wash the leaves before cooking. You can use the leaves as you would cabbage leaves. Peel off the outer skin from the bulb using a paring knife and eat the bulb raw or cook as you do a turnip.

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When to Harvest Kohlrabi

  • Harvest spring planted kohlrabi when the enlarged stem is 1 to 2 inches (2.5-5 cm) in diameter.
  • Harvest summer and autumn planted kohlrabi when the stem is 3 to 4 inches (7-10 cm) in diameter.
  • Harvest giant kohlrabi varieties when they are 8 to 10 inches (20-25 cm) in diameter.
  • Kohlrabi that ripens in mild and cool weather will be tastier than kohlrabi that matures in warm and hot weather. Where summers are cool, grow kohlrabi spring through autumn. Where summers are hot, grow kohlrabi in fall and winter.
  • Kohlrabi that matures in cool weather can remain in the ground until temperatures fall into the 20°sF (-6°C). Garden-stored kohlrabi can freeze once or twice in winter and still be edible.

Harvest a kohlrabi stem by cutting it from the base of the plant with a serrated knife.


These Sputnik-shape vegetables may look alien, but their fast growth and great taste make them something every gardener should try in their garden. Here’s how to plant, grow, and harvest kohlrabi!

About Kohlrabi

A cool-season biennial and member of the Brassica family (alongside broccoli, cabbage, brussels sprouts, and many others), kohlrabi is grown for its nutritious, bulb-shaped stem. The stem is crisp, sweet, and tender, making it a great addition to salads or stir-fries. In terms of taste, think of kohlrabi as a milder turnip.

Given the right conditions, kohlrabi is easy to grow, matures quickly (in as little as 6 weeks), and is generally pest-free. Give it a try!

Planting Dates for KOHLRABI

Planting

When to Plant Kohlrabi

  • Kohlrabi is a cool-season crop, so it is best grown in the cooler weather of spring or fall. In warmer regions such as the southern U.S., it may be grown as a winter crop, too.
  • For an early to mid-summer harvest, sow kohlrabi seeds indoors in early spring, 6 to 8 weeks prior to your last spring frost date. Stagger plantings every 2 to 3 weeks for a continuous harvest. Harden off seedlings before planting outdoors, too.
  • Alternatively, sow seeds directly into the garden once soil temperatures have reached at least 45°F (7°C).
  • For a fall or winter harvest, sow seeds outdoors in mid- to late summer.

Choosing and Preparing a Planting Site

  • Plant in full sun.
  • Nutrient-rich, well-draining soil will produce the best results.
    • Tip: Because it can be grown in shallower soils, kohlrabi is a great alternative to turnips or rutabagas.
  • Soil pH should be slightly acidic to neutral (6.0 to 7.0), though kohlrabi is tolerant of slightly alkaline soils (7.0 to 7.5), too.
  • Avoid planting kohlrabi where other vegetables in the Brassica family have been grown in the previous 2 or 3 years. This helps to prevent the spread of disease and nutrient deficiencies.
  • Kohlrabi isn’t a heavy feeder, but will benefit from having a bit of aged manure or compost worked into the soil prior to planting. Use about 1 inch of fertilizing material per 1 square foot of soil.

How to Plant Kohlrabi

  • Sow seeds ¼ to ½ inch deep.
  • In rows, space kohlrabi seeds about 2 inches apart, thinning to about 6 inches apart once seedlings have emerged. Space rows themselves 10 to 12 inches apart.

Watch a video on planting and growing kohlrabi:

How to Grow Kohlrabi

  • Hot summer temperatures will stress the plant and hamper the growth of the bulb-like stem.
  • If humidity is low, help to keep the soil moist by spreading a thin layer of straw or bark mulch around the base of the plant.
  • Water 1 inch per square foot per week, unless the soil seems to be drying out sooner.
  • Be diligent about weeding around kohlrabi, but be careful not to disturb its roots while the plant is still young.

Pests/Diseases

  • Aphids
  • Black rot
  • Cabbage loopers
  • Cabbage root maggots
  • Cabbage worms
  • Clubroot
  • Cutworms
  • Flea beetles
  • Downy mildew
  • Powdery mildew
  • Thrips


Aphids are a common pest of kohlrabi and other members of the cabbage family (Brassicas). Photo by GrowVeg.

Harvest/Storage

How to Harvest Kohlrabi

  • To harvest, cut the kohlrabi root off at ground level when the bulbous stems are between 2 and 4 inches in diameter.
  • The stem should be succulent, tender, and sweet at this size. If allowed to become too large, it can become tough and bitter.

How to Store Kohlrabi

  • Harvested stems can be stored with other root crops in a cool, humid place or in the refrigerator for up to 4 weeks. Remove the leaf stems and wash the stem thoroughly before storing.


Photo by GrowVeg


A Three (Or Four) Season Kohlrabi Harvest

In regions with the mildest winters, kohlrabi will prosper from fall through spring. Tucker Taylor, manager of Woodland Gardens in Winterville, Ga., grows a number of crops year-round for Atlanta-area chefs and farmers markets, but kohlrabi is a cool-season standard.

“We like it because it’s so quick,” he says. “We rotate it through our hoop houses [plastic-covered tunnels] from fall through spring, and harvest the bulbs at different stages.” Taylor’s crew first starts the seeds in a greenhouse using Sunshine Mix, an organic seed-starting medium. “We add a little kelp to the mix to provide micronutrients,” he says. The seedlings are then transplanted into the hoop houses about a month later full-size bulbs are harvested about six weeks after that.

Taylor also grows baby ‘Purple’ kohlrabi greens year-round in a greenhouse, which is heated only enough to keep the tender greens from freezing on extra-cold nights.

“The kohlrabi serves as the base of our microgreens mix, which also includes red mustard, broccoli, ‘Red Russian’ kale, red amaranth and arugula,” he explains. “It adds bright color to the mix and is very easy to grow.”

For his savory mix, Taylor grows the various greens individually in open flats filled with earthworm castings. When the greens are about 10 to 12 days old, he snips the leaves with scissors just above soil level, blends them together, and bags them for sale.


Harvest Time – Kohlrabi

Back in April, I posted about kohlrabi, called colinabo in Spanish, a new-to-me crop in my backyard. Amongst the photos I shared were the two below, showing kohlrabi sprouted indoors (left) and a sprout from seed sowed directly in the garden bed (right):

Kohlrabi sprouted indoors (April 25, 2020) Kohlrabi sprouted in garden bed (April 25, 2020)

I transferred the indoor sprouts to individual paper cups, and a couple of weeks later, I transplanted them to the same bed as the ones sowed directly. In the photo below, a transplanted seedling with the top of the paper cup kept as a protective collar (left) next to two direct-sow seedlings:

Kohlrabi seedlings (May 11, 2020)

I moved one of the direct-sow seedlings to a pot, to avoid crowding later on. At that point, the direct-sow seedlings seemed way behind in development compared to the ones sprouted indoors, but just a week later, they had quietly, yet quickly, pretty much caught up:

Kohlrabi seedlings (May 19, 2020)

I removed the paper collars and topped up all the seedlings with a bit of extra soil a few heavy-rain days, and then regular watering, helped them all to grow strong. Below is a series of photos following one plant, from the beginning of swelling of the stem, to maturity:

Fully grown kohlrabies are so alien looking, very decorative in the garden bed. The more common varieties have a light green exterior mine are purple, so shiny, they could be displayed as gems next to rubies or diamonds:

Kohlrabi ready for harvest (July 6, 2020)

Although both the sprouted-indoors and the direct-sow crops developed well, the latter seemed to have grown slightly larger, in average one example is the same pair I was following, since the beginning:

Fully grown kohlrabi sprouted indoors shown left, and slightly larger, directly sown, right (July 6, 2020)

The one I transplanted to a pot back in May is still alive, although it is growing much slower than the rest of the crop:

plant transplanted to a pot in May (June 25, 2020)

This means that sprouting indoors is not necessary, and that growth is generally better in the ground, so next year I will just sow all the kohlrabi seed in the garden bed (in mid April for my 6B Northern Hemisphere gardening zone.) I have heard that it is recommended to harvest kohlrabi when it has reached the “size of a tennis ball” (the official diameter range being 6.54–6.86 cm 2.57–2.70 inches) before they start aging and become woody t he largest ones in my crop were about 7.2 cm (2.8 inches), so I felt like I had to oblige and harvest those right away. Bonnie Plants™ actually quotes a more reasonable range, between 2.5 and 4 inches (6.35 and 10.16 cm), but I could hardly wait to taste my new crop, anyway, so I harvested two right away. I will be sharing my findings in the kitchen soon.


Growing Kohlrabi in the Home Garden

There is no need to raise seeds in punnets as they will germinate easily direct in the ground. Seedlings will transplant successfully to a new position which is a great way to prevent waste when thinning out and creates more plants for you to enjoy.

Sow seeds during the spring, summer and fall (autumn). The plants will tolerate light frosts during the winter months.

Kohlrabi likes a full sun to part shade position with moist soil. They can be grown successfully in a shade house in warm climates which helps to retain the moisture in the soil.

Most varieties of kohlrabi take 55 to 75 days to mature depending on your climatic conditions.

Harvest kohlrabi when the bulbous stem at the base of the plant is 2 inches (5cm) wide. Any larger and they can become woody with the exception of Giant varieties which can reach up to 4 inches (10cm) wide or larger and still be edible.

Young kohlrabi plants will need to be protected from aphids, slugs and caterpillars.

Planting, Plant Care and Harvesting Kohlrabi

Tools and Materials Needed

  • Kohlrabi Seeds – Try these organic Early White Vienna Kohlrabi Seeds on Amazon (Paid link)
  • Shovel
  • Trowel
  • Aged Manure or Compost
  • Garden Lime (Only necessary for acid soils)
  • Mulch
  • Liquid Fertilizer – This 10 Lb pack of Miracle-Gro Soluble Plant Food is great value. (Paid link)
  • Snail Bait and Vegetable Dust(Paid links)

Instructions

How to grow kohlrabi from seed in the home garden.

First prepare the soil by digging in aged manure or compost. Add a few handfuls of garden lime if needed. Make a wide trench with your trowel with rows spaced 16 inches (40cm) apart then make a line down the middle of each trench with your finger 1/4 inch (5mm) deep.

Sprinkle the kohlrabi seeds along the line then gently backfill the soil. Water well with a mist spray then keep moist.

Thin out the seedlings so each plant is 8 inches (20cm) apart.

Transplant Seedlings (Optional)

To transplant seedlings wait until they have their second leaves before transplanting to a new position. Keep the roots moist to prevent transplant shock. Mulch around the kohlrabi to prevent water loss.

After 2 weeks apply a half strength liquid fertilizer then apply a full strength dose every 2 weeks. This will encourage growth and create healthier plants.

Protect young plants from from snails by sprinkling snail bait around the plants. If aphids or caterpillars become a problem sprinkle vegetable dust on the leaves.

Harvest the kohlrabi when the bulbous base reaches 2 inches (5cm) wide. Cut the tap root underneath the bulbous stem with a sharp knife.

To avoid chemicals in your garden either use an organic vegetable dust or try this guide to making a Natural Aphid Spray using stinging nettles.

Are you looking to grow more vegetables in your garden? Try these guides to growing Leeks, Bok Choy (Pak Choi) or Rutabaga (Swede).

For more information see this guide to Vegetable Gardening or to get more out of your home try this Homesteading guide.

Do your garden tools need replacing or do you know someone who loves gardening? This 49 piece heavy duty Garden Tool Set has everything you could possibly need and comes with an attractive tote bag. (Paid link)

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