Wisconsin’s cool climate makes early spring the best time to plant kale, as it thrives in temperatures below 80 degrees. Knowing the best time to plant kale in Wisconsin can mean the difference between a bumper crop and a sad, bolted mess. You want leaves that are sweet, tender, and ready for harvest, not tough and bitter.
Kale is a cold-hardy superstar. It actually tastes better after a light frost. That’s why timing matters so much in the Badger State. Whether you’re a beginner or a seasoned gardener, this guide will walk you through every step.
Best Time To Plant Kale In Wisconsin
The short answer is: early spring, as soon as the soil can be worked. For most of Wisconsin, that means late March through mid-April. But you also have a second window in late summer for a fall harvest. Let’s break it down by region and season.
Spring Planting Window
Kale seeds can germinate in soil as cold as 40°F. That’s key. You don’t need to wait for the last frost date. In fact, kale seedlings can handle a light freeze down to about 28°F.
- Southern Wisconsin (Madison, Milwaukee, Kenosha): Plant seeds outdoors from March 20 to April 15.
- Central Wisconsin (Wausau, Stevens Point): Aim for April 1 to April 20.
- Northern Wisconsin (Eau Claire, Green Bay, Superior): Wait until April 15 to May 1.
If you want a head start, you can start seeds indoors 4 to 6 weeks before your last frost date. Use a seed-starting mix and keep them under grow lights. Transplant them outside when they have 4 true leaves and the soil is workable.
Fall Planting Window
Fall kale is often sweeter than spring kale. The cool nights and shorter days concentrate sugars. For a fall crop, plant seeds 6 to 8 weeks before your first expected frost.
- Southern Wisconsin: Plant from July 25 to August 15.
- Central Wisconsin: Plant from July 15 to August 5.
- Northern Wisconsin: Plant from July 1 to July 20.
Fall kale can survive under snow. Many gardeners harvest it well into November or even December. Just cover it with row cover if a hard freeze is predicted below 20°F.
Understanding Wisconsin’s Climate Zones
Wisconsin spans USDA hardiness zones 3b to 5b. That’s a big range. The northern part of the state has a shorter growing season, about 100 to 120 days. The south has 140 to 160 days. This affects when you plant.
Zone 3B And 4A (Northern Wisconsin)
Here, the last spring frost can be as late as May 20. The first fall frost can come as early as September 10. You have a narrow window. Focus on spring planting and use fast-maturing varieties like ‘Red Russian’ or ‘White Russian’. These mature in 50 to 60 days.
Zone 4B And 5A (Central And Southern Wisconsin)
You have more flexibility. You can plant a spring crop, then a fall crop, and even a winter crop under protection. Varieties like ‘Lacinato’ (dinosaur kale) and ‘Winterbor’ do well here. They are cold-tolerant and produce for months.
How To Plant Kale Step By Step
Once you’ve picked your planting window, follow these steps for success.
Step 1: Prepare The Soil
Kale likes rich, well-drained soil with a pH between 6.0 and 7.5. Test your soil if you can. If not, mix in 2 to 3 inches of compost before planting. Work it into the top 6 inches of soil.
Add a balanced fertilizer like 10-10-10 at a rate of 1 pound per 100 square feet. Or use an organic option like fish emulsion or blood meal.
Step 2: Sow Seeds Or Transplants
For seeds, plant them 1/2 inch deep and 1 inch apart. Cover lightly with soil and water gently. Once seedlings have 4 leaves, thin them to 12 to 18 inches apart. You can eat the thinnings.
For transplants, dig a hole slightly larger than the root ball. Place the plant at the same depth it was in the pot. Space them 12 to 18 inches apart. Water well after planting.
Step 3: Water Consistently
Kale needs about 1 to 1.5 inches of water per week. Water at the base of the plant to avoid wet leaves, which can cause disease. Use a soaker hose or drip irrigation if possible.
Step 4: Mulch And Feed
Apply a 2-inch layer of straw or shredded leaves around the plants. This keeps the soil cool and moist. Side-dress with compost or a balanced fertilizer every 3 to 4 weeks during the growing season.
Best Kale Varieties For Wisconsin
Not all kale is created equal. Some handle cold better. Some grow faster. Here are the top picks for Wisconsin gardens.
- ‘Winterbor’: Very cold-hardy, down to -10°F. Curly leaves, great for fall and winter harvest.
- ‘Lacinato’ (Dinosaur Kale): Tender, dark blue-green leaves. Tolerates heat and cold. A favorite for salads.
- ‘Red Russian’: Flat, fringed leaves with purple stems. Fast-growing, matures in 50 days. Sweet after frost.
- ‘Starbor’: Compact, upright growth. Good for small spaces. Very productive.
- ‘Toscano’: Similar to Lacinato but more heat-tolerant. Good for spring planting.
Common Mistakes And How To Avoid Them
Even experienced gardeners make errors. Here are the most common ones with kale in Wisconsin.
Planting Too Late In Spring
If you plant kale in May or June, it will bolt when summer heat hits. Bolting means the plant sends up a flower stalk and leaves turn bitter. Stick to early spring or late summer planting.
Overcrowding
Kale needs space. If you plant too close, leaves stay small and plants compete for nutrients. Thin to at least 12 inches apart. For larger varieties, go 18 inches.
Neglecting Pests
Cabbage worms, aphids, and flea beetles love kale. Use row cover for the first few weeks. Check the undersides of leaves weekly. Spray with neem oil or insecticidal soap if needed.
Harvesting Wrong
Don’t pull the whole plant. Harvest the outer leaves first, leaving the inner rosette to keep growing. This gives you a continuous harvest for weeks.
Harvesting Kale At The Right Time
You can start harvesting baby kale leaves when they are about 3 inches long, usually 30 days after planting. For full-sized leaves, wait until they are 8 to 10 inches long, about 50 to 75 days after planting.
Always harvest from the bottom up. Leave at least 4 to 6 inner leaves to keep the plant growing. In fall, wait until after a light frost for sweeter flavor. Kale can be harvested even after snow covers it.
Extending The Season With Protection
Wisconsin winters are harsh, but you can extend your kale harvest well into winter with simple protection.
Cold Frames
A cold frame is a box with a glass or plastic top. Place it over your kale bed in late fall. It traps heat and blocks wind. You can harvest kale all winter in a cold frame, even in zone 4.
Row Cover
Floating row cover is a lightweight fabric that lets light and water through. It adds 4 to 6 degrees of frost protection. Use it in early spring to warm the soil, or in fall to delay frost damage.
Mulch Heavily
After the ground freezes, pile 6 to 8 inches of straw or leaves over the plants. This insulates the soil and keeps roots alive. In early spring, remove the mulch and you’ll have fresh kale weeks before neighbors.
Frequently Asked Questions
Can I plant kale in the summer in Wisconsin?
It’s not recommended. Summer heat above 80°F makes kale bitter and tough. If you must plant in summer, choose a heat-tolerant variety like ‘Toscano’ and provide afternoon shade.
How late can I plant kale in Wisconsin for fall?
You can plant as late as mid-August in southern Wisconsin, and mid-July in the north. The key is to have 6 to 8 weeks before the first hard frost.
Do I need to start kale indoors?
No, kale grows well from direct seeding. But starting indoors gives you a 2 to 3 week head start, which helps in short-season areas.
Can kale survive Wisconsin winter?
Yes, with protection. Under snow or row cover, kale can survive down to 10°F. In a cold frame, it can last all winter. The leaves may freeze, but they thaw and are still edible.
What is the best kale variety for beginners in Wisconsin?
‘Winterbor’ is the most forgiving. It’s cold-hardy, disease-resistant, and produces heavily. ‘Red Russian’ is also easy and fast.
Final Tips For Success
Kale is one of the easiest crops for Wisconsin gardens. The key is timing. Plant too early and you risk a late freeze. Plant too late and you get bitter leaves. Stick to the windows above, and you’ll have sweet, tender kale for months.
Water consistently, watch for pests, and harvest regularly. Kale will keep producing until the ground freezes solid. And if you protect it, you can even eat fresh kale from your garden in January.
So grab your seeds, check your zone, and get planting. Your taste buds will thank you.