Maine’s short, cool summers make early spring planting critical for a full kale harvest. Knowing the best time to plant kale in maine is the difference between a bumper crop and a disappointing patch of stunted leaves. This guide gives you the exact timing, step-by-step methods, and insider tips for growing kale successfully in Maine’s unique climate.
Kale thrives in cool weather. It actually tastes sweeter after a light frost. So timing your planting right means you get tender, flavorful leaves from late spring through the fall.
Best Time To Plant Kale In Maine
The short answer is: plant kale seeds outdoors 4 to 6 weeks before the last spring frost. For most of Maine, that means mid-April to early May. But you also have a second window in late summer for a fall harvest.
Let’s break down the specifics for your region and growing method.
Spring Planting Window For Southern Maine
Southern Maine (zones 5b-6a) has a slightly longer growing season. Your last frost date typically falls between May 1 and May 15.
- Direct sow seeds outdoors: April 15 to May 1
- Transplant seedlings (started indoors): April 20 to May 10
- Use row covers or cold frames: March 25 to April 15
Kale seeds germinate in soil as cool as 40°F. So you can push the envelope a bit. Just watch the weather forecast. A hard freeze below 20°F can damage young plants.
Spring Planting Window For Central And Northern Maine
Central Maine (zones 5a-5b) and Northern Maine (zones 4a-4b) have shorter, colder springs. Your last frost date is usually May 15 to June 1.
- Direct sow seeds outdoors: May 1 to May 20
- Transplant seedlings: May 10 to May 25
- Use cold frames or indoor starts: April 20 to May 10
In Aroostook County and other northern areas, wait until soil temps reach at least 45°F. A soil thermometer is a cheap investment that saves you from planting too early.
Fall Planting Window For All Maine Regions
Fall kale is often the best kale. The cold temps convert starches to sugars, giving you sweeter leaves. For a fall harvest, plant 6 to 8 weeks before the first fall frost.
- Southern Maine: Direct sow July 20 to August 15
- Central Maine: Direct sow July 15 to August 5
- Northern Maine: Direct sow July 1 to July 25
Fall planting is easier because the soil is warm. Seeds germinate quickly. And you don’t have to worry about frost killing mature plants. Kale can handle temps down to 20°F without much damage.
Why Timing Matters So Much In Maine
Maine’s growing season is short. In northern areas, you might only have 90 to 110 frost-free days. Kale needs about 50 to 75 days to reach full size. If you plant too late in spring, summer heat will make the leaves tough and bitter.
If you plant too early in fall, the leaves might bolt (go to seed) before winter. Getting the timing right ensures you harvest tender leaves for months.
Understanding Maine’s Frost Dates
Your local frost dates are your best guide. Here are approximate dates for major Maine regions:
- Portland (south): Last spring frost April 25, first fall frost October 15
- Augusta (central): Last spring frost May 10, first fall frost October 1
- Bangor (east): Last spring frost May 15, first fall frost September 25
- Presque Isle (north): Last spring frost June 1, first fall frost September 10
Check your specific zip code using the USDA Plant Hardiness Zone map or your local extension office. These dates are averages. A late frost in May can still happen, so always have row covers ready.
How To Plant Kale In Maine: Step-By-Step
Once you know the best time to plant kale in maine, follow these steps for a successful crop.
Step 1: Choose The Right Kale Variety
Not all kale varieties handle Maine’s conditions equally. Pick cold-hardy types that mature quickly.
- Winterbor: Very cold hardy, good for fall harvests
- Red Russian: Tender leaves, matures in 50 days
- Lacinato (Dinosaur): Traditional Italian variety, tolerates heat and cold
- Dwarf Blue Curled: Compact, good for small spaces, matures in 55 days
- Siberian Kale: Extremely cold tolerant, great for northern Maine
Step 2: Prepare The Soil
Kale likes rich, well-draining soil with a pH between 6.0 and 7.5. Maine’s soil is often acidic. Test your soil pH and add lime if needed.
- Clear the area of weeds and rocks
- Dig in 2 to 3 inches of compost or well-rotted manure
- Add a balanced fertilizer (10-10-10) at planting time
- Rake the bed smooth
Step 3: Sow Seeds Or Transplants
For spring planting, you can start seeds indoors 4 to 6 weeks before your last frost. Use seed-starting mix and keep them under grow lights or in a sunny window.
For direct sowing:
- Plant seeds 1/4 to 1/2 inch deep
- Space seeds 1 inch apart in rows 18 to 24 inches apart
- Water gently after planting
- Thin seedlings to 12 to 18 inches apart when they have 2 true leaves
For transplants:
- Harden off seedlings over 5 to 7 days
- Dig holes 12 to 18 inches apart
- Plant at the same depth as the pot
- Water well after transplanting
Step 4: Water And Mulch
Kale needs consistent moisture. Water 1 to 1.5 inches per week. In Maine’s spring, rainfall often provides enough. But during dry spells, supplement with drip irrigation or a soaker hose.
Mulch around plants with straw or shredded leaves. This keeps soil cool, retains moisture, and suppresses weeds. In northern Maine, mulch also protects roots from early frosts.
Step 5: Fertilize And Care
Kale is a heavy feeder. Side-dress with compost or a nitrogen-rich fertilizer every 3 to 4 weeks. Fish emulsion works well and is organic.
Watch for pests like cabbage worms and aphids. In Maine, flea beetles can be a problem in spring. Use row covers to protect young plants. Handpick caterpillars or use insecticidal soap for aphids.
Harvesting Kale At The Right Time
You can start harvesting baby kale leaves when the plant is about 8 to 10 inches tall. Pick the outer leaves first, leaving the inner rosette to keep growing. This method gives you a continuous harvest for weeks.
For full-sized leaves, wait until the plant has 10 to 12 mature leaves. Cut leaves from the bottom up. Never harvest more than one-third of the plant at once.
In Maine, you can often harvest kale well into November. After a hard frost, the leaves get sweeter. Cover plants with row covers or a cold frame to extend the season even further.
Common Mistakes Maine Gardeners Make
Even experienced growers slip up sometimes. Here are the most common errors with kale planting in Maine.
- Planting too late in spring: Summer heat ruins the flavor
- Planting too early in fall: Bolting happens if temps stay warm
- Overcrowding: Thin seedlings ruthlessly for good air flow
- Ignoring soil pH: Acidic soil stunts growth
- Not hardening off transplants: Sudden cold shock kills young plants
- Forgetting row covers: Frost can damage unprotected seedlings
Extending The Kale Season In Maine
With a little effort, you can harvest kale from April through December. Here’s how.
Use Cold Frames
A simple cold frame extends your spring planting by 3 to 4 weeks. Build one with old windows or buy a kit. Place it over your kale bed in late March. The soil warms faster, and plants stay protected from frost.
Try Overwintering
In southern Maine, some kale varieties survive winter under heavy snow or mulch. Plant in late summer, then cover with 6 to 8 inches of straw in November. In early spring, remove the mulch and you’ll have fresh kale weeks before anyone else.
Succession Planting
Plant a new batch of kale every 2 to 3 weeks from spring through mid-summer. This gives you a steady supply of young, tender leaves. Stop planting by early August in northern areas to allow time for fall harvest.
Frequently Asked Questions
Can I plant kale in Maine in August?
Yes, but only for a fall harvest. In southern Maine, plant by August 15. In northern Maine, plant by July 25. Later plantings may not mature before hard frost.
What is the latest I can plant kale in Maine?
For a fall harvest, the latest is about 8 weeks before your first expected fall frost. For most of Maine, that’s mid-August in the south and late July in the north. You can also plant in late September under a cold frame for a winter harvest.
Does kale need full sun in Maine?
Kale grows best in full sun (6 to 8 hours daily). But in Maine’s short summers, partial shade is okay, especially in southern areas. In northern Maine, full sun is essential for good growth.
How cold can kale tolerate in Maine?
Mature kale can survive temps down to 20°F. Young seedlings are more sensitive and need protection below 25°F. After a hard frost, kale leaves get sweeter but the plant may stop growing.
Should I start kale indoors or direct sow in Maine?
For spring planting, starting indoors gives you a head start. Direct sowing works fine for fall planting when soil is warm. In northern Maine, indoor starts are almost essential for a full spring harvest.
Final Tips For Maine Kale Growers
Kale is one of the easiest crops for Maine’s climate. Once you nail the timing, you’ll have fresh greens for months. Keep these final points in mind.
Always check your local frost dates before planting. Use a soil thermometer to confirm soil temps. And don’t be afraid to experiment with different varieties. Some years, Red Russian might outperform Winterbor, and vice versa.
Remember that kale is a biennial. If you leave a few plants in the ground over winter, they’ll produce yellow flowers in spring. The bees love them. And you can collect seeds for next year’s planting.
One more thing: kale grown in Maine’s cool weather is often more nutritious than store-bought kale. The stress of cold temps increases antioxidant levels. So you’re not just growing food; you’re growing superfood.
Start planning your kale patch now. Mark your calendar for the right planting dates. Prep your soil. And get ready for the best kale you’ve ever tasted. With the best time to plant kale in maine dialed in, you’re set for success.