When to Plant Kohlrabi in Minnesota (2026 Guide)
Kohlrabi is a unique and nutritious vegetable that can thrive in Minnesota's varied climates. Known for its swollen stem, this versatile brassica offers a delicious crunch and is perfect for slaws, salads, and cooked dishes. With the median last spring frost as late as May 17 in some areas, timing is critical for successful planting and harvest in this state.
Minnesota's frost dates vary significantly across different USDA hardiness zones. For example, Zone 6a, which includes cities like Burnsville, experiences a median last spring frost on April 30 and an October 5 first fall frost, allowing for a robust growing season. Meanwhile, those in Zone 5a, such as Bemidji, must navigate a shorter growing season with a last frost around May 17.
Understanding when to plant kohlrabi is vital for gardeners looking to maximize their harvest. By utilizing the favorable conditions in spring and fall, you can ensure your kohlrabi reaches its ideal size—around 3 inches in diameter—prior to the first fall frost. This guide will help you navigate the planting schedule and care for this exciting crop.
Planting Schedule by USDA Zone in Minnesota
| Zone | Indoor start | Transplant out | Direct sow | Harvest |
|---|---|---|---|---|
| Zone 6a | Start seeds indoors from March 1 – March 15, ~6 weeks before April 30. | Transplant outdoors from April 10 – May 15, after the last frost risk. | Sow seeds directly outdoors from May 1 – May 15. | Harvest from June 15 – September 30, ideally when bulbs are about 3 inches. |
| Zone 5b | Start seeds indoors from February 20 – March 10, ~6 weeks before May 4. | Transplant outdoors from April 25 – May 20, ensuring the last frost has passed. | Sow seeds directly outdoors from May 1 – May 20. | Harvest from June 1 – September 15 for the best quality. |
| Zone 5a | Start seeds indoors from February 1 – February 15, ~6 weeks before May 17. | Transplant outdoors from May 10 – May 20, after the last frost risk. | Sow seeds directly outdoors from May 15 – June 1. | Harvest from June 15 – September 1 to catch the perfect size. |
Kohlrabi Planting Windows in Minnesota
- Indoor start: You should start kohlrabi seeds indoors from February 1 to March 15, depending on your local zone in Minnesota.
- Transplant outdoors: Transplant kohlrabi outside from April 10 to May 20, ensuring you avoid frosts according to your zone.
- Harvest: Harvest your kohlrabi from June 1 to September 30, ideally when the bulbs are around 3 inches in diameter.
Common Mistakes Growing Kohlrabi in Minnesota
- Many Minnesota gardeners underestimate the impact of late spring frosts. In some regions, frost can linger far longer than expected, delaying the start of the growing season.
- Not considering soil temperature can lead to poor seed germination. Minnesota's soil may take longer to warm, affecting how quickly seeds sprout, particularly kohlrabi, which prefers cooler conditions.
- Some growers neglect to space kohlrabi properly, leading to overcrowding that can stunt growth. Ample space is critical for their bulb development, especially in Minnesota gardens where plants often compete for limited nutrients.
- Failing to harvest kohlrabi at the right time can diminish flavor and texture. Waiting too long might result in woody bulbs, which can deter enjoyment—make sure to check regularly.
- Ignoring the seasonal humidity in Minnesota can strain plant health. High humidity levels can lead to disease, so providing adequate air circulation is vital during humid summer months.
Frequently Asked Questions
What if I'm in a cold pocket of Minnesota?
If you live in a cold pocket, consider starting kohlrabi seeds indoors earlier or selecting faster-maturing varieties. You can then transplant them as soon as the danger of frost has passed to maximize your season.
Can I still plant kohlrabi in May?
Planting kohlrabi in May is fine, especially in the more temperate zones. Just ensure that you are after the last frost date in your area, like May 17 for Zone 5a, to avoid damage.
How often should I water kohlrabi?
Kohlrabi thrives with consistent moisture. Water when the top inch of soil feels dry. In Minnesota's varying climates, adjust your watering frequency based on seasonal humidity and rainfall to prevent stress on the plants.
What pests should I watch for when growing kohlrabi?
Common pests include aphids and cabbage worms, which can affect kohlrabi. Monitor your plants regularly and use row covers or organic pesticides as a preventative measure, especially early in the season.
Can I eat kohlrabi greens?
Absolutely! Kohlrabi greens are edible and nutritious, just like kale or collard greens. Use them in stir-fries, soups, or sauté them with garlic for a tasty side dish.
Keep Learning
City guides in Minnesota
Other crops in Minnesota
Typical fall sowing window for Kohlrabi in Minnesota: July 25 – August 15.