Kohlrabi Does Not Form A Tuber: What To Do?

Kohlrabi is a popular type of cabbage, so it is grown in many gardens. The most delicious part is the tuber. But what if none develops? Learn here what to do when kohlrabi does not form a tuber.

  • Tuber is the edible part in kohlrabi
  • grows above ground and is formed by primary growth of the shoot axis in thickness
  • size, color and shape of the tuber vary depending on the variety
  • the most effective help against failure of tuber formation is to recognize causes and prevent them
  • avoid care mistakes, increase resistance, protect against diseases

What is the reason?

If the kohlrabi does not form a tuber, it may have different causes. In most cases, planting and care errors are responsible. For example, the kohlrabi may have been planted too deep or spacing between plants may not have been maintained. Other causes may be fertilization that is too heavy on nitrogen or temperatures that are too cool. In addition, failure to follow crop rotation and associated cabbage hernia can prevent tuber formation, as can so-called heartlessness or the purchase of inferior plants.

Tip: With kohlrabi, by the way, the leaves are also edible, they contain even more healthy ingredients than the tuber.

Pay attention to planting depth and spacing

Plants that do not develop tubers can really only be disposed of. To avoid having this problem with new plants, it is important to avoid causes such as planting too deep. It’s best to plant them just as deep as they were in the pot before, about two to four inches deep. At least as important are the distances between the plants. Here, about 30 cm is recommended.

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Kohlrabi im Gemüsebeet

Tip: If the planting is too dense, when the seedlings may not have been singled, the kohlrabi plants can not form tubers, because there is simply not enough space.

Avoid nitrogenous fertilization

Incorrect or overly nitrogen-emphasized fertilization can also lead to problems with tuber formation, preventing it completely or partially.

  • Too much nitrogen causes plants to shoot to seed
  • tubers are not formed or only partially formed
  • Help is promised by fertilization in line with requirements
  • suitable are liquid fertilizers or organic fertilizers
  • commercially available liquid fertilizers are effective for a short period of time
  • therefore apply once a week
  • organic fertilizers have a long-term effect
  • fertilize only once during the entire cultivation period
  • at best at the beginning of the culture directly at the planting

Tip: A lack of nutrients or water can also cause the kohlrabi plants to start flowering and not develop tubers. Therefore, they should be watered regularly during the complete culture.

Protection from heartlessness

Cold plays a role in that when cultivating young plants or growing them, it can cause not only cracking and bursting, but also the fact that kohlrabi does not form a tuber.

Kohlrabi-Jungpflanzen in Anzuchtgefäßen
  • Temperatures below twelve degrees problematic
  • consequence can be so-called heartlessness
  • occurs mainly in spring
  • with a too cold cultivation and sensitive varieties
  • vegetation point stops growing early
  • plant no longer forms new leaves
  • shoots into the height or into the herbage
  • tubers are not formed
  • Remedy only by preventive measures
  • Kohlrabi plants need warmth
  • pay attention to germination temperatures of 18-20 degrees
  • after germination 12-14 degrees recommended
  • Protect from cabbage hernia
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Cabbage hernia is a so-called crop rotation disease. It can also cause the kohlrabi not to form a tuber. It is caused by a parasite that can survive in the soil for several years and infect the roots of cruciferous plants, which include kohlrabi. One of the most important measures to protect against these pathogens is to observe and maintain crop rotation. This means that kohlrabi should be grown at the earliest every four, and preferably every seven years, in the same location or where other cruciferous plants were.


Use high-quality plants

If the kohlrabi does not develop tubers, it may be due to low-quality plant material. Kohlrabi plants that are offered for sale in spring are often planted in small pots in groups of several. In some cases, they stand cramped in these planters for several weeks. This leads to the fact that they can not develop and shoot up exclusively. At some point they are overdue, i.e. they are actually fully developed in terms of age, but have practically skipped the tuber formation stage.

Tip: When buying kohlrabi plants, you should also make sure that the root ball is firm, the leaves are healthy and lush green, and there are already small visible nodules. It is best to buy them from a gardener or garden centers, here the quality is usually better.

Frequently asked questions

How long does it take for tubers to form?

Depending on when you plant them, early varieties can be harvested from April/May and late varieties into October/November. It can take six to twelve weeks from sowing to harvest maturity of the first tubers.

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From when can you precrop kohlrabi plants?

Pre-cultivation is possible from mid-February? Before you finally plant them out around mid-April, you should harden them off for about ten days by putting them outside during the day and bringing them back in at night. Or you can cover it with fleece overnight.

How can you tell if a tuber is inedible?

If the kohlrabi stands in the ground until the leaves wilt, it is usually only good for cooking out. Also, if the tubers are already woody, they are usually inedible.

Can tuber formation be promoted by ideal planting partners?

Actually, some plants can be conducive to tuber formation or growth, provided the kohlrabi plants themselves are of good quality. Good neighbors include radishes, bush beans, or marigolds and marigolds. The latter are known for their pest-repellent properties.


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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