When To Start Seedlings In Maine

Getting your timing right is the first step to a great garden here in Maine. Knowing exactly when to start seedlings in Maine can mean the difference between a bountiful harvest and a disappointing one. Our short growing season means we have to be smart and strategic. This guide will walk you through the simple steps to figure out your personal planting calendar.

We’ll cover your last frost date, which plants need a head start indoors, and how to make a simple schedule. You’ll learn how to work with Maine’s unique climate, not against it. Let’s get your garden planning started.

This heading is your cornerstone. All your seeding dates flow from this one piece of information. For most of Maine, the average last spring frost falls between mid-May and early June. Coastal areas might see it in mid-May, while inland and northern regions often wait until early June.

You must look up your specific town’s date. Use the University of Maine Cooperative Extension as a trusted resource or check with your local gardening club. Once you have that date, you can count backwards to find your seed starting day.

Your Essential Seed Starting Timeline

Here is a general timeline based on a last frost date of May 30th. Adjust the numbers based on your own date.

10-12 Weeks Before Last Frost (Early to Mid-March): Start your slowest growers. This includes onions from seed, leeks, celery, and herbs like parsley and oregano.
8-10 Weeks Before Last Frost (Late March to Early April): Time for most of your favorite summer veggies. This is when you start peppers, eggplant, and tomatoes. Also, start annual flowers like marigolds and petunias.
4-6 Weeks Before Last Frost (Late April): Start faster-growing crops like broccoli, cabbage, and cauliflower if you didn’t buy transplants. This is also prime time for cucumbers, melons, squash, and pumpkins—they grow fast and dislike root disturbance.
2-4 Weeks Before Last Frost (Early to Mid-May): Harden off all your indoor seedlings! This is also the time to direct seed cool-weather crops like peas, spinach, and carrots right into the garden soil.

Plants You Should Always Start Indoors

Some plants simply need that long, warm head start to produce a harvest in our climate. Trying to direct seed these after the last frost will leave you with tiny plants by fall.

Tomatoes
Peppers
Eggplant
Tomatillos
Onions (from seed)
Most annual herbs and flowers

Plants Best Sown Directly in the Garden

Other plants have delicate roots or grow so quickly that starting them indoors is more trouble than its worth. They prefer to go right into the ground.

Root crops (carrots, radishes, beets, parsnips)
Corn
Beans and peas
Leafy greens (lettuce, spinach, arugula)
Cucumbers, squash, and pumpkins (can be started indoors, but must be done carefully in large pots)

A Step-by-Step Guide to Starting Seeds

Follow these steps for healthy, strong seedlings ready for Maine’s summer.

Step 1: Gather Your Supplies

You don’t need fancy equipment. Essentials include:

Clean containers with drainage holes (seed trays, yogurt cups, etc.)
A quality seed-starting mix (not garden soil)
Seeds
Labels and a waterproof marker
A warm place for germination (top of the fridge works)
A bright light source (south window or simple shop lights)

Step 2: Planting and Germination

Moisten your seed-starting mix before filling your containers. Plant seeds at the depth recommended on the packet—usually 2-3 times the seed’s width. Cover the trays with a plastic dome or plastic wrap to keep humidity high. Place them in that warm spot and check daily for sprouts.

Step 3: The Critical Light Phase

As soon as you see green, move the trays immediately under bright lights. This is non-negotiable in Maine’s often cloudy spring. Keep lights just 2-3 inches above the seedlings and run them for 14-16 hours a day. Weak, leggy seedlings are usually crying out for more light.

Step 4: Watering, Feeding, and Potting Up

Water from the bottom to avoid disturbing the tiny seedlings and to prevent disease. Let the soil surface dry slightly between waterings. Once seedlings get there first set of true leaves (the ones that look like the plant), you can start feeding with a half-strength liquid fertilizer every week or two. If plants outgrow there starter cells, transplant them into slightly larger pots.

Step 5: Hardening Off

This is the most important step Maine gardeners sometimes skip. You cannot take seedlings from your cozy house and plant them directly outside. They will get sunburned and shocked.

About 10-14 days before planting, start taking trays outside.
Place them in a sheltered, shady spot for just 1-2 hours the first day.
Gradually increase their time outside and their exposure to sun and breeze over the week.
By the end, they should be able to handle full sun and wind all day and night (as long as it’s above freezing).

Common Maine Seed Starting Challenges

Every gardener faces hurdles. Here’s how to tackle Maine-specific ones.

Leggy, Weak Seedlings

This is almost always due to insufficient light. Get those lights closer or invest in a brighter fixture. Cool room temperatures can also contribute.

Damping Off (Seedlings Collapse)

This fungal disease thrives in cool, wet soil. Use clean containers, provide good air circulation with a small fan, and avoid overwatering to prevent it.

Running Out of Space

We all get excited! Be realistic about how many tomato plants you can truly fit. A few healthy seedlings are better than dozens of cramped, struggling ones. A simple wire shelving unit with lights on each shelf can double your space.

Your Maine Month-by-Month Checklist

Print this and stick it on your fridge.

March

Finalize your garden plan and order seeds.
Gather and clean your seed-starting supplies.
Start onions, leeks, celery, and slow herbs by mid-month.

April

Start tomatoes, peppers, and eggplant early in the month.
Start broccoli and cabbage if desired.
Begin hardening off cool-weather crops you started earlier.
Direct sow peas and spinach in the garden as soon as soil is workable.

May

Start cucumbers, melons, and squash indoors in large pots.
Harden off all indoor seedlings for at least a week.
After your last frost date, transplant hardened-off seedlings.
Direct sow beans, corn, carrots, and beets.

FAQ: Seed Starting in Maine

What is the average last frost date for my area?
It varies widely. Portland is around May 10th, Bangor around May 15th, and Caribou around May 30th. Always verify for your exact location.

Can I start seeds on a windowsill?
A very bright, south-facing window might work, but our spring is often cloudy. Most gardeners need supplemental lights for stocky, healthy plants.

When should I start flower seeds for Maine gardens?
Follow the same timeline as vegetables. Slow-growing flowers like pansies can be started 10-12 weeks before last frost. Fast-growing ones like zinnias are best started 4-6 weeks before.

My seedlings stopped growing after I transplanted them. What happened?
This is often transplant shock. Ensure you hardened them off properly, water them in well after planting, and protect them from a surprise cold snap with a cloche or row cover.

Is it to late to start seeds in May?
For warm-season crops like tomatoes and peppers, yes, it’s likely too late for a good harvest. But you can still start quick crops like beans, squash, and cucumbers, or fast-growing greens for a fall harvest.

By following this Maine-specific guide, you give your garden the best possible start. The key is patience—waiting for the right time to start, and then patiently hardening off your plants. With a little planning, you’ll be enjoying homegrown Maine tomatoes and more before you know it.