This site may contain affiliate links. to read our full disclosure, click here. Now let’s read on and learn how to grow kohlrabi from seed
Introduction on how to grow kohlrabi from seed
Kohlrabi, a member of the brassica family, isn’t really well known.
The plant is a medium-sized plant with the taste of a mild turnip. it really is worth growing although not many know this plant.
The plant deserves some attention though as it is really easy to grow. it also grows really fast. And it can be grown in the colder periods of the year.
A really good reason to plant this vegetable in the vegetable garden is the fact that you can eat the bulb and the leaves. So you get more harvest from the same plant. Both the leaves and the bulb can be eaten raw or cooked.
what is a kohlrabi?
Kohlrabi, German turnip, or turnip cabbage, is a member of the kale family. It’s a “man-made” form like the other Brassica oleracea plants.
The plant matures in about 60 days. And it’ll way about 150 grams or 5.30 oz. The bulbs are best harvested when they are about 5 centimeters in size. Bigger plants tend to be quite woody and not as tasty.
where to grow kohlrabi?
The plants love a loose soil with quite a bit of nutrient. The soil can be kept moist but not wet.
Kohlrabi loves a lot of sunlight and will thrive if you give it more than 6 hours of full sun a day. Especially really early in the spring and really late in the fall, the plant needs as much light as it can get.
When to grow kohlrabi?
You can start seeds about 5 weeks before the last frost in spring. The plants are cold-loving plants so they don’t mind.
Kohlrabi can also be grown in the fall and you can sow the last seeds about 6 weeks before the first frost date.
taking care of kohlrabi
Direct sowing is advised but to me, it’s not the best option. Still, I’m explaining how to direct sow your kohlrabi here. I will be discussing sowing indoors in the transplanting section of the article.
You can sow the seeds quite close together and thin out the plants afterward. This will make sure that you have at least one plant in every available space.
Sow at a depth of about 1/4th of an inch or half a centimeter deep. Cover lightly and make sure the seeds are kept moist all the time until they sprout.
Start by sowing your kohlrabi in rows. About 15 to 20 seeds per foot is a good average. At a size of 5 inches or 12 centimeters, you can thin out the plants to about 5 inches apart.
If you plant in rows, keep about a foot between each row. The square foot gardening method will allow the same spacing of 5 inches in width and in length.
Kohlrabi can easily be grown from seedlings indoors. Contrary to radishes, starting seedlings in small containers can have some advantage to sowing directly in the ground.
Just like sowing outside, you can sow the seeds about 1/4th of an inch deep or half a centimeter deep.
Grow the seedlings until they are about 5 inches or 12 centimeters before you plant them outside.
Many times, starting indoors will give you a faster harvest. And growing indoors can be done earlier than sowing outside.
I already mentioned that kohlrabi should be harvested when the immature bulbs are about 2 inches or 5 centimeters diameter.
Leaving the plants too long will give you a woody bulb with really thick skin and less taste. Be careful because there is a giant variety and this one will grow bigger and still be harvestable.
To harvest the kohlrabi, just snip off the plant underneath the bulb. You can also harvest the young leaves to eat raw or cooked.
diseases and pests in how to grow kohlrabi from seed
the mealy cabbage aphid
The mealy cabbage aphid or Brevicoryne brassicae can give the plant a growth shock as it sucks necessary moisture and nutrients out of the plants. The aphids can also bring different diseases onto the plants by spreading it through their saliva.
Aphids tend to come back time after time and every gardener has to deal with them sooner or later. While sucking out the life of your plants, aphids can spread diseases with their saliva.
You can treat the infestation with a hard spray of water or with a homemade insecticidal soap mixture. In any case, you’ll have to treat several times. Keep an interval of 3 to 5 days for 3 to 4 times to kill off the critters and the eggs.
the big cabbage butterfly
The big cabbage butterfly or Pieris brassicae can devastate the plants while in caterpillar stadium.
The caterpillars can eat through the leaves until there’s only a stem left. Using insect-screen can avoid a lot of trouble. In case it’s too late and the plants are infested with caterpillars, it’s possible to use spinosad. Just make sure you read the manual before using because it does have an impact on the soil and other insects. Use it in the evening when there’s no bees around.
I personally don’t grow that many plants. So I can easily remove the caterpillars by hand. Read this article to see what I do.
The small cabbage butterfly
The small cabbage butterfly or Pieris rapae also has a devastating effect on brassica’s, the caterpillar can, just like the caterpillar of his bigger cousin, kill the plants when not timely treated. Insect screen is the way to go. If you’re too late, spinosad can be used.
If you want to have more in-depth information on the cabbage worm, click to this article.
Alticini or flea beetles will devastate the leaves of your plants. They will eat small holes all over the leaves. You can easily treat the beetles with neem oil.
If you clean up in the autumn after the harvest, you can already prevent a lot of problems because the beetle pupae overwinter in the debris on the ground.
There’s a possibility if you have a first attack that you’ll get a second attack after a couple of months. So check the plants in a timely fashion.
One fungus that is quite common is downy mildew or Peronospora parasitica. Bordeaux mixture can prevent the disease from growing but once the fungus is developing, only the removal of the infested plants will help contain the disease. Also, be careful when using Bordeaux mix because this is borderline organic.
There are several bacterial and fungal diseases that can threaten your kohlrabi plants. Use crop rotation to prevent this disease.
Brassica sp. Bacterial Soft Rot Erwinia carotovora subsp. carotovora
The disease is called Soft Rot because the Erwinia uses special enzymes to soften the plant tissue. So, it’s immediately clear what problem you’re facing. The leaves will get soft spots that will spread. The odor is quite bad.
The plant will eventually die from this disease.
The only way to treat soft rot is by choosing disease-resistant plants and making sure the seeds are disease free.
As many of these diseases, this disease can also overwinter in plant debris in the winter.
Closing on how to grow kohlrabi from seed
I didn’t write about all the diseases and pests that can threaten your kohlrabi plants. But I will amend the article when I come across a disease that isn’t mentioned.
So this is it for this article on how to grow kohlrabi in the backyard. I hope you’ve found it interesting. If so, please share on social media, with friends, and other gardeners.
If you want to be notified when I put on new articles or video’s, please subscribe to my newsletter on the right side of this page.
Thanks for reading and see you in the next post.