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
Essential seed starting supplies
You don't need a fancy setup. Here's what actually matters: For more details, see our guide on When to start seeds indoors.
- Seed starting mix: Not potting soil, not garden soil. Seed starting mix is fine-textured, sterile, and drains well. 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 from year to year after a quick bleach rinse.
- Light: A 4-foot shop light with daylight bulbs (6500K) hung 2-3 inches above seedlings. Total cost: about $25. LED grow lights work great too but aren't required.
- Heat mat: Optional for most crops, essential for peppers and eggplant. Raises soil temperature by 10-15°F. About $20 for a standard mat.
- 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.
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 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
For customized dates based on your exact location, use the planting calendar tool. It calculates everything automatically from your zip code. And for more on getting seedlings outside safely, read the seed starting timeline for beginners.
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