Learn About Plant Spacing For Kohlrabi


By: Liz Baessler

Kohlrabi is a weird vegetable. A brassica, it’s a very close relative of better known crops such as cabbage and broccoli. Unlike any of its cousins, however, kohlrabi is known for its swollen, globe-like stem that forms just above the ground. It can reach the size of a softball and looks a lot like a root vegetable, earning it the name “stem turnip.” Though the leaves and the rest of the stems are edible, it is this swollen sphere that is most commonly eaten, both raw and cooked.

Kohlrabi is popular across Europe, though it’s less often seen in English speaking countries. That shouldn’t deter you from growing this interesting, tasty vegetable. Keep reading to learn more about growing kohlrabi in the garden and kohlrabi plant spacing.

Plant Spacing for Kohlrabi

Kohlrabi is a cool weather plant that grows well in the spring and even better in the fall. It will flower if temperatures fall below 45 F. (7 C.), but it will get woody and tough if they stay above 75 F. (23 C.). This makes the window for growing them quite small in a lot of climates, especially considering that kohlrabi takes about 60 days to mature.

In the spring, seeds should be sown 1 to 2 weeks before the average last frost. Sow seeds in a row at a depth of half an inch (1.25 cm.). What’s a good distance for kohlrabi seed spacing? Kohlrabi seed spacing should be one every 2 inches (5 cm.). Kohlrabi row spacing should be about 1 foot (30 cm.) apart.

Once the seedlings have sprouted and have a couple of true leaves, thin them to 5 or 6 inches (12.5-15 cm.) apart. If you’re gentle, you can move your thinned seedlings to another spot and they will probably keep growing.

If you want to get a head start on cool spring weather, plant your kohlrabi seeds indoors a few weeks before the last frost. Transplant them outdoors about a week before the last frost. Plant spacing for kohlrabi transplants should be one every 5 or 6 inches (12.5-15 cm.). There’s no need to thin transplants.

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Growing kohlrabi in home gardens

Kohlrabi (Brassica oleracea var. gongylodes) is an odd-looking garden plant. It has a bulbous, enlarged stem just above the soil surface, topped with upright thick leaves.

In the kitchen, you can serve kohlrabi raw as part of a raw vegetable platter, sliced into a salad or grated into a slaw. You can also slice and use it in stir-fries or sautés. Delicious kohlrabi is crunchy, juicy, and has a mild, sweet, “cabbage” flavor. Once harvested, the leaves are also tasty. You can use the leaves as cooking greens.

The same species as cabbage, cauliflower, broccoli, turnip and kale, kohlrabi has many of the same gardening needs. It does best in cool weather, between 65°F and 75 °F, and when planted in fertile, moisture-retentive soil.

Soil pH and fertility

Soil testing and fertilizer

  • Grow kohlrabi in loamy, well-drained soil with high organic matter.
  • You can grow acceptable crops on heavier soil as long as it is well-drained, and on sandy soil if you water it often.
  • Have your soil tested.
  • A neutral soil pH of 6.0 to 7.5 is ideal.
    • Apply phosphorus (P) and potassium (K) according to soil test recommendations. Many Minnesota soils have enough phosphorus.
    • Unless your soil test report specifically recommends additional phosphorus, use a low- or no-phosphorus fertilizer.
  • Improve your soil by adding well-rotted manure or compost in spring or fall.
  • Do not use fresh manure as it may contain harmful bacteria and increase weed problems.
  • If you use manure or compost, you may not need more fertilizer applications, depending on how much organic matter you use.
  • Side-dress with fertilizer when the plants are about four inches tall.
  • Do not use any fertilizer containing a weed killer ("Weed and Feed"), as it may kill your vegetable plants.

Planting

For a spring crop, choose a variety with a low number of days to harvest. Look for days to harvest of 35 and 45 on the seed packet. It is better to grow giant kohlrabi as a fall crop.

Starting seeds indoors

Some gardeners begin kohlrabi indoors to get an early start.

  • Start seeds indoors in early April, or four to six weeks before transplanting.
  • There is no need to use a heating mat as you might for other seeds. Cool room temperatures between 60°F and 70°F and bright overhead light will result in the best growth of the plants.
  • High temperatures cause rapid growth rate, producing tall, weak plants that are difficult to handle without causing damage.
  • Apply fertilizer to developing seedlings when the first true leaf appears. Use a half-strength starter solution once a week. After two true leaves are present, apply fertilizer twice a week.
  • When the plants have four or five true leaves, reduce watering. Place plants outside where they will receive wind protection and a couple hours of sunlight.
  • Gradually expose them to more sunlight over the next week or two, bringing them indoors if night temperatures drop below 40°F.
  • Dig small holes with a trowel, or dig a narrow trench with a shovel.
  • Place the seedlings four inches apart, and fill the soil around them so that the plant is at the same level it was in its pot.
  • Water the plants in, or use a transplant starter solution high in phosphorus and low in nitrogen and potassium.

Plant seed directly in the garden in July. Giant kohlrabi takes about two months to mature. A late July planting will be ready to harvest before a hard freeze.

  • Plant seed shallowly at one-fourth to one-half inch, three seeds every four inches.
  • Keep the soil moist during seedling emergence.
  • After the seedlings emerge, thin to one plant every four inches, or every 12 inches for giant types.
  • Take care of the seedlings, as they experience extreme heat, wind, drought and insects when they are most vulnerable. Water them as needed.
  • Space giant kohlrabi four inches apart until they are two inches in width, then harvest some of them so that there are 12 inches between plants. The plants that remain will grow to eight or ten inches in width over the next few weeks.

A row cover will protect the plants from wind and insects during the first weeks of growth. Use a lightweight material so that temperatures do not get too hot under the cover.

If strong winds loosen a floating row cover, it can do more damage than the plants would suffer without it. Anchor it firmly with soil and/or pins at the edges. You can also support the row cover with wire hoops.


Importance of garden spacing:

There are several good reasons which tell us the importance of garden spacing. The right garden spacing will:

Reduce competition: Garden spacing help to reduce the competition for the sunlight that is vital for growth. If the plant grows in the intensive form they compete with each other for sunlight which results in, they utilize more nutrients to improve its vegetative growth of vegetables rather than go for reproductive growth which ultimately affects the yield of the vegetable garden.

Conservation of water: Shade may help to conserve water during the hot summer days, but if you plant everything too closely together, the plants will end up fighting available water. Ultimately by perfect garden spacing tell us how much water you can afford to use to keep your plants healthy.

Availability of nutrients: Proper spacing ensures each vegetable gets the maximum amount of available nutrients.

Protection from weeds: It reduces the number of weeds in your vegetable garden. In this way, they give a natural sort of protection against weeds.

Better growth: Your plants are going to grow more and bigger leaves as they grow. These leaves will generate a canopy that increases the quantity of shade that reaches their lower sections. The proper amount of plant spacing aids to ensure the entire plant takes plenty of healthy sunshine. In turn, this will help to certify you have robust plants that bear lots of vegetables.

Plant population calculation: Garden spacing also give you vegetable plant count which also help to understand whether the growing vegetable sufficient for your family need or not.


Planting Kohlrabi

Kohlrabi skin can be green, white, or purple. Source: Mariam

Trying to determine how to grow kohlrabi the best way? The first step is planning the best start for the plant. After all, it won’t grow well if it’s in the wrong location or planted at the wrong time!

Kohlrabi plants do well in cool weather conditions. The best time to plant kohlrabi seeds is 3 to 4 weeks before the predicted date for the last spring frost, or earlier if you’ll be starting them indoors. These vegetables take 45 to 60 days to mature. As kohlrabi can survive an early frost, warm-climate dwellers can sow seeds in the late summer or early fall for a crop in the cool weather of autumn. Warm locations like southern California can grow kohlrabi all winter long!

Sow seeds directly in the ground or start them indoors for transplants. Live kohlrabi plants should be transplanted into the garden a little before the final frost date, so begin hardening them off to the outdoor temperatures in advance. Your seedlings should be four to six weeks old at the time of transplant for best success.

Select a full-sun location for your kohlrabi. While kohlrabi can be grown in containers, it may require more frequent watering and fertilization, so keep that in mind. We recommend growing yours in raised beds with fertile, well-draining soil.

Traditional spacing for growing kohlrabi is 9-12 inches apart, in rows spaced at least the same amount of inches apart. However, square-foot gardeners have been known to use intensive kohlrabi plant spacing, with as many as nine plants per square foot. This usually leaves only about 3 inches apart between individual plants, but can really increase the quantity you’re able to plant.

But now that we’ve discussed spacing kohlrabi, how to plant is essential to cover as well. For sowing kohlrabi seeds, plant ¼” deep with just a light dusting of soil overtop. Once they’ve germinated, thin to your preferred spacing by cutting off excess sprouts with pruning snips.

Growing kohlrabi from transplants starts similarly, but once you have 4-6 week old transplants of kohlrabi growing, you can put them out into the garden once they’ve been hardened off. Plant at the same depth they were in their pot. Avoid even allowing an inch deep of soil to build up around the bulbous base for these plants, their bulb actually forms above ground, with only their cabbage-like roots underneath. Space at your preferred kohlrabi spacing as covered above.

All parts of the kohlrabi are edible, from the leaves to the bulbous base. Source: Chris and Jenni

So now we’ve covered planting, and you’ll be asking how to grow kohlrabi for the best results. Let’s talk about elements like your garden soil and other important factors for good growth!

Sun and Temperature

These plants require full sun… the more, the better. Make sure you choose a spot in your garden that receives at least 6 hours of full sunlight every day. The ideal temperature range for growing Kohlrabi is 40°F to 75°F (4.4°C to 23.9°C).

The plant is heat-sensitive, and conditions that are too warm can make the bulb turn woody. Make sure that the temperature is not higher than 75°F (23.9°C) during the harvesting season for the peak flavor. Kohlrabi can be grown in USDA growing zones 3 to 10.

Watering and Humidity

When considering how to grow kohlrabi, remember these plants need quite a bit of moisture to supply those bulbs, stems, and leaves. Keep the soil moist at all times, applying more water when the first inch of soil dries out. A soaker hose is ideal for watering your kohlrabi plants.

An inch of water per week is recommended, but if the weather’s rainy, you can skip watering as nature will handle it.

Kohlrabi needs fertile and well-drained soil to grow and produce healthy stems, leaves, and its bulbous base. Mulch the soil with plenty of organic matter for added nutrition and water absorption. Loose, well-worked soil is best for your kohlrabies to truly shine!

The ideal soil pH level for growing kohlrabi ranges from 6.0 to 6.8.

Fertilizing

Fertilizing kohlrabi is a little tricky as they’re heavy feeders. Start with rich soil, to begin with, and side-dress every few weeks with well-rotted cow manure. Alternately, begin with the rich soil but opt for regular fertilization using a nitrogen-rich fertilizer. A 10-5-5 should suffice, but follow manufacturer’s instructions for the frequency of application.

When growing kohlrabi in containers, regular fertilization is a must as they will drain the soil of nutrients regularly. However, they have shallow but large root systems, so apply your fertilizer in a ring around the plant so that it does not make contact with the bulbous stem base. The same is true of in-ground fertilization, but there’s less risk of water washing the fertilizer back against the plant in a normal bed setting.

Liquid fertilizers are also an option, but only if your soil will retain the dissolved nutrients. If you have ample supplies of organic matter in the soil, regular applications of liquid fertilizer will work.

Pruning

Pruning is not necessary when growing kohlrabi except for harvesting purposes.

Propagation

Kohlrabi is typically propagated through seeds only. Other methods of propagation just don’t result in good, healthy plants. Opt to grow kohlrabi from seeds from a reliable supplier.


Troubleshooting Common Growing Problems

The kohlrabi plant can be attacked by cabbage loopers, cutworms, flea beetles, cabbage aphids, and imported cabbage worms. Spraying bacillus thuringiensis can help to control cabbage worms.

Placing collars around the stem can give aid in protecting seedlings form cutworm damages. Carefully remove egg clusters, which are normally found underneath the leaves, and wash the plant with a diluted soap solution.

The kohlrabi plant is susceptible to black rot, black leg, downy mildew, clubroot, and cabbage yellows. Carefully remove or destroy any infected plants.


Almost any article on companion planting references the Native American “Three Sister Planting”. This age old grouping involves growing corn, beans and squash – often pumpkin – in the same area. As the corn stalks grow, beans naturally find support by climbing up the stalk. Beans, as all legumes, fix nitrogen in the soil, which supports the large nutritional needs of corn. Squash grows rapidly and the large squash leaves shade out weeds and serve as natural weed block. Good plant companions work in support of each other.

Many long time gardeners swear that growing certain plants together improves flavor as well. While science hasn’t found support for some of the benefits of companion planting, there is support for the above information. Garden wisdom and experience supports these traditional beneficial plant companions.


Watch the video: Kohlrabi Seed Germination u0026 Growth Time Lapse - Soil cross section - Growing Plant


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