When to Plant Kohlrabi in Iowa (2026 Guide)
Kohlrabi is a unique and versatile vegetable that many gardeners are beginning to explore. Its bulb-like stem offers a flavorful and crisp texture that can elevate various dishes, from slaws to roasted veggies. If you're in Iowa, understanding when to plant kohlrabi is essential for a successful harvest, especially considering the state's frost dates.
For those in Zone 6a, the median last spring frost date is April 25, while gardeners in Zone 6b can expect it on April 14. By starting your kohlrabi plants at the right time, you can ensure they thrive in Iowa's climate. With an approximately 164- to 188-day frost-free season depending on your specific zone, timing your planting is crucial.
This guide covers everything you need to know about planting and harvesting kohlrabi in Iowa. With the right techniques and timing, you can enjoy this delicious vegetable in your garden. Let’s dig into the details you’ll need to plan your kohlrabi crops effectively.
Planting Schedule by USDA Zone in Iowa
| Zone | Indoor start | Transplant out | Direct sow | Harvest |
|---|---|---|---|---|
| Zone 6a | Start indoors February 15 – March 1, ~6–8 weeks before April 25 | Transplant outdoors April 26 – May 10, after the last frost | Direct sow seeds between April 26 – May 10 for early summer crops | Harvest from June 10 – July 5 when bulbs are about 3 inches in diameter |
| Zone 6b | Start indoors February 1 – 15, ~6–8 weeks before April 14 | Transplant outdoors April 15 – 25, after the last frost | Direct sow seeds between April 15 – 25 for early summer crops | Harvest from June 25 – July 20 when bulbs are about 3 inches in diameter |
Kohlrabi Planting Windows in Iowa
- Indoor start: Start your kohlrabi seeds indoors between February 15 and March 1 for best results in Iowa.
- Transplant outdoors: Transplant your kohlrabi outdoors from April 15 to April 25, just after the last spring frost.
- Harvest: You can expect to harvest kohlrabi from June 10 through July 20 when the bulbs reach about 3 inches in diameter.
Common Mistakes Growing Kohlrabi in Iowa
- Many Iowa gardeners underestimate the power of late spring frosts. Planting too early can lead to frost damage on young kohlrabi plants, so always pay attention to local frost dates.
- Not providing enough spacing between kohlrabi plants is a common mistake. Make sure to allow at least 6-8 inches between plants to encourage healthy growth and avoid overcrowding in Iowa’s humid summers.
- Ignoring soil health is a big mistake gardeners make in Iowa. Kohlrabi requires well-draining soil enriched with organic matter. Conducting a soil test is advisable to determine your soil's pH and nutrient levels.
- In Iowa, novice gardeners might think that kohlrabi is only a spring crop. However, this vegetable can be successfully planted again for a fall harvest in late summer, taking advantage of the cooler temperatures before frost.
- Another frequent oversight is assuming all kohlrabi varieties will grow well in Iowa. Purple varieties tend to be more heat-tolerant and can be more forgiving than green varieties during the hot summer months.
Frequently Asked Questions
What should I do if my kohlrabi plants experience frost?
If your kohlrabi plants are hit by frost, check for any wilting or browning. Light frost can be tolerable, but severe frost might damage the bulbs. If so, consider replanting for a second chance at a harvest.
Can I plant kohlrabi in May?
While it’s possible to plant in May, it's essential to ensure it won't get too hot for the plants. Aim for a fall planting if your summer temperatures are consistently high to prevent bolting.
What if I'm in a cold pocket of Iowa?
If you're situated in a cooler area, you may want to start your seeds indoors earlier. Keep an eye on local frost dates to avoid early outdoor planting that could jeopardize your kohlrabi.
Is kohlrabi easy to grow in Iowa?
Yes, kohlrabi is generally easy to grow in Iowa, as long as you adhere to frost dates and provide suitable soil conditions. Its quick growth makes it approachable for both novice and seasoned gardeners.
How long does it take for kohlrabi to mature?
Kohlrabi typically takes about 45 to 60 days from transplant for bulbs to reach their optimal size. Keep an eye on their growth to ensure timely harvesting for the best flavor.
Keep Learning
City guides in Iowa
Other crops in Iowa
Typical fall sowing window for Kohlrabi in Iowa: July 29 – August 19.