The right answer for what month to start seeds indoors is 6 to 8 weeks before your local last frost. For most folks that lands from late January to early April. Your zone and crop mix shift the date.
Each January I pull out a fresh paper calendar. I circle the date my last frost falls on. Then I count back 8 weeks and mark my pepper start day. I sow peppers first because their seeds sprout slow and need the longest head start.
Your seed starting calendar rides on your USDA hardiness zone. Zone 5 folks begin in March since the last frost sits in mid-May. Zone 9 growers can sow in January with a frost date in February. Zone 7 sits in the middle, around late February.
Getting last frost date timing right shapes the whole season. Seedlings need the right age when they hit the garden. Too early and they get root-bound. Too late and they miss the prime growing weeks.
I learned this the hard way my first spring. I started my tomatoes 10 weeks out and ended up with floppy giants that flopped over in their cups. Now I stick to the 6 to 7 week mark and the plants go in stocky and strong.
Peppers and Eggplant
- Weeks before frost: Start these 8 weeks before your last frost. The seeds need warm soil and take 10 to 14 days to sprout.
- Why early: Slow sprouting and slow early growth mean they need the longest head start of any common garden crop you grow.
- Ideal temp: Keep the soil at 80°F (27°C) with a heat mat to push sprouting to the fastest rate.
Tomatoes
- Weeks before frost: Sow 6 to 7 weeks ahead of your last frost. Plants stand strong but not leggy at transplant time.
- Why this window: Earlier than 7 weeks and the seedlings outgrow their cells. Later than 6 and they miss the early push.
- Pot size: Bump up to 4-inch pots at week 4. Roots get room and the plants do not stunt before garden day.
Brassicas
- Weeks before frost: Cool-season crops like broccoli and cabbage want 8 weeks indoors before they go out in cool spring weather.
- Cold tolerance: These tough plants handle light frosts after you harden them off. Move them out 2 weeks before last frost.
- Harvest payoff: Early starts mean heads form before summer heat triggers bolting and ruins the flavor of the crop.
Cucurbits
- Weeks before frost: Squash, cucumbers, and melons need only 3 to 4 weeks indoors before transplant time.
- Root sensitivity: These crops hate root disturbance. Quick indoor starts in bigger cells avoid transplant shock.
- Outdoor timing: Wait until soil hits 65°F (18°C) before you move them out. Growth stalls in cold soil.
Build your own custom schedule with a free online frost date tool from your local extension office. Print a blank monthly calendar and mark each crop's sow date by counting back from your frost date.
I keep my printout on the fridge next to the seed shelf. This one habit turns chaotic spring sowing into a smooth weekly routine. My success rate jumped once I made the switch from guesswork to a real plan.
Read the full article: Starting Seeds Indoors: 10 Steps for Success
