When to Plant Kohlrabi in Maine (2026 Guide)

Kohlrabi is a unique and versatile vegetable that can thrive in Maine's variable climate. With a growing season that starts after the last frost, the optimal time to plant kohlrabi varies depending on your specific location. In Portland, for example, you can expect the last spring frost around May 8, making it an ideal window to start your kohlrabi planting adventure.

This crunchy brassica can be sown directly or started indoors before being transplanted outdoors. Given that kohlrabi matures in just 45 to 60 days, gardeners can enjoy fresh bulbs well into the growing season. With a frost-free period of around 150 days in Portland, there's no need to rush — but it's crucial to plan effectively to avoid the impending fall frosts.

Kohlrabi is a great choice for both early spring and late summer planting, allowing for harvesting during the cooler months. Selecting the right varieties can enhance your garden's yield and diversity. Remember, preparing your planting schedule around local frost dates such as May 8 for spring and October 5 for fall is essential for optimal harvest.

Planting Schedule by USDA Zone in Maine

Zone	Indoor start	Transplant out	Direct sow	Harvest
Zone 5b	Start seeds indoors from March 15 – March 30, ~6–8 weeks before May 8.	Transplant outdoors around May 15 – May 20, after the last frost.	Direct sow seeds from May 15 – June 15 for a summer crop.	Harvest kohlrabi from July 15 – August 30.
Zone 6a	Start seeds indoors from March 1 – March 15, ~6–8 weeks before April 27.	Transplant outdoors around April 27 – May 5, after the last frost.	Direct sow seeds from May 5 – June 15 for a summer crop.	Harvest kohlrabi from June 15 – August 15.

Kohlrabi Planting Windows in Maine

Indoor start: For best results, start your kohlrabi seeds indoors from March 1 to March 30 in Maine, allowing optimal growth before outdoor transplanting.
Transplant outdoors: Transplant your kohlrabi seedlings outdoors between May 15 and May 20, once the risk of frost is minimal.
Harvest: Harvest your kohlrabi between July 15 and August 30, when the bulbs reach about 3 inches in diameter for the best flavor.

Common Mistakes Growing Kohlrabi in Maine

One common mistake is planting kohlrabi too late in Maine. With the last frost on May 8, many newcomers don't realize they need to start indoors in March to avoid missing the planting window.
Overwatering is another issue for many Maine gardeners. Due to the region's sometimes humid conditions, it’s easy to water too frequently, which can lead to rot and poor plant health.
Failing to consider frost can hurt kohlrabi growth in Maine. With the first fall frost anticipated around October 5, ensure all seeds are harvested ahead of time to avoid damaging your crop.
Many gardeners in Maine forget that kohlrabi benefits from nutrient-rich soil. A soil test prior to planting ensures your bed has sufficient organic matter and nutrients, leading to healthier plants.
Crowding kohlrabi can restrict growth. Ensure to space them properly as they mature, especially when interplanting with other crops like tomatoes or peppers, to maximize yield without causing competition.

Frequently Asked Questions

What if I'm in a colder spot in Maine?

If you're in a cooler area, start your kohlrabi seeds indoors a bit earlier in late February. This will give them a head start before transplanting when soil warms up properly.

Can I still plant kohlrabi in late May?

Yes, you can still plant kohlrabi in late May, but aim for direct sowing rather than transplanting. If conditions allow, this can help ensure successful harvesting in the later summer months.

How often should I water kohlrabi?

Water kohlrabi regularly, about once or twice a week, depending on your soil type and weather. Maintaining consistent moisture is crucial, especially in warmer weather, to keep bulbs from becoming woody.

What pests should I watch for?

Keep an eye out for aphids and cabbage worms, which can negatively impact kohlrabi. Regularly inspecting leaves and using floating row covers can help deter these pests.

Is it too late to try kohlrabi in fall?

If you plant kohlrabi in late summer, you'll be able to harvest before the first fall frost around October 5. Ensure you have a fast-maturing variety for the best success!