Indoor Seed Starting Schedule by Zone

Starting seeds indoors gives you a massive head start on the growing season, saves money compared to buying transplants, and opens up variety options you'll never find at a garden center. But timing is everything. Start too early and you end up with leggy, root-bound seedlings. Start too late and you might as well have direct-seeded.

This schedule is organized by weeks before your last frost date. Find your zone in the table below, note your approximate last frost, then count backward.

Last frost dates by zone

Zone	Typical last frost
4	May 15 – May 30
5	April 30 – May 15
6	April 10 – May 1
7	March 25 – April 15
8	March 1 – March 30
9	January 25 – February 15

The master seed starting timeline

Count weeks backward from your last frost date:

Weeks before last frost	What to start	Notes
12-14 weeks	Onions, leeks, celery	These are slow growers. They need the longest head start.
10-12 weeks	Peppers (hot and sweet), eggplant	Peppers are slow to germinate. Use a heat mat — 80-85°F soil temp.
8-10 weeks	Artichokes, rosemary	Both need cold stratification or long lead times.
6-8 weeks	Tomatoes, tomatillos, ground cherries	The sweet spot for most gardeners' main crop.
6-8 weeks	Broccoli, cauliflower, cabbage, Brussels sprouts	For spring transplanting. Start a second round in summer for fall crops.
4-6 weeks	Lettuce, kale, Swiss chard, collards	Can also direct seed, but transplants establish faster.
4-6 weeks	Herbs: basil, parsley, cilantro	Basil is frost-sensitive. Don't transplant until 2 weeks after last frost.
3-4 weeks	Cucumbers, squash, melons	These grow fast. Starting too early makes weak, overgrown transplants.
2-3 weeks	Flowers: marigolds, zinnias, cosmos	Or direct seed after frost. Indoor starting gives an earlier bloom.

What this looks like for each zone

Zone 5 (last frost ~May 5)

January 25 – February 5: Onions, leeks
February 10 – February 25: Peppers, eggplant
March 1 – March 15: Tomatoes, brassicas
March 20 – April 1: Lettuce, herbs
April 5 – April 15: Cucumbers, squash

Zone 7 (last frost ~April 5)

January 1 – January 10: Onions, leeks
January 15 – January 30: Peppers, eggplant
February 1 – February 15: Tomatoes, brassicas
February 20 – March 5: Lettuce, herbs
March 5 – March 15: Cucumbers, squash

Try our Seed Starting Calendar by ZIP Code

Enter your ZIP code to see exactly when to start each crop indoors and when to move it outside, counted back from your last spring frost — indoor start, transplant, and direct-sow windows for 40+ vegetables, herbs, and flowers.

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Essential seed starting supplies

You don't need a fancy setup. For more details, see our guide on when to start seeds indoors. Here's what actually matters.

Seed starting kit and what it costs

Seed starting mix

Fine-textured, sterile, well-draining — not potting or garden soil. A 16-quart bag runs about $8 and lasts most of the season.

Cell trays or pots

72-cell flats for small seeds; 6-cell packs or 3" pots for tomatoes and peppers. Reuse yearly after a quick bleach rinse.

Light

A 4-foot shop light with daylight bulbs (6500K) hung 2-3 inches above seedlings. About $25. LED grow lights also work but aren't required.

Heat mat

Optional for most crops, essential for peppers and eggplant. Raises soil temperature by 10-15°F. About $20.

Timer

Set lights for 14-16 hours per day. A basic outlet timer costs $8.

Common seed starting mistakes

Starting too early: The number one mistake. A tomato seedling that's been growing indoors for 12 weeks is worse off than one that grew for 6 weeks. Root-bound plants struggle to establish.
Not enough light: Windowsills aren't bright enough, even south-facing ones in winter. Seedlings stretch toward the glass and end up thin and floppy. Use supplemental lights.
Overwatering: Keep soil moist but not wet. If the surface is constantly damp, you'll get damping off — a fungal disease that kills seedlings at the soil line.
Skipping hardening off: Indoor seedlings need 7-10 days of gradual outdoor exposure before transplanting. Start with a couple hours of shade, increase to full sun over a week.
Planting everything at once: Different crops need different lead times. The table above exists for a reason — follow it.

!Don't start too early

When in doubt, start later rather than earlier. An undersized transplant catches up fast once it's in warm soil, but a leggy, root-bound seedling rarely recovers.

When to just direct seed

Not everything benefits from indoor starting. These crops do better (or just as well) planted directly in the garden. For more details, see our guide on the seed starting timeline for beginners.

Beans and peas — they hate root disturbance
Corn — needs to be direct seeded in blocks
Root crops (carrots, radishes, turnips, beets) — transplanting mangles the roots
Dill — bolts quickly when transplanted
Potatoes — planted from seed potatoes, not seeds

Get dates for your exact location

For customized dates based on your zip code, use the planting calendar below. It calculates everything automatically. For more on getting seedlings outside safely, read the seed starting timeline for beginners.

Try our Free Vegetable Planting Calendar by ZIP Code

Enter your ZIP code for a free, personalized planting calendar. See when to start seeds, transplant, and harvest 45+ vegetables, herbs, and flowers based on your USDA hardiness zone and frost dates.

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