Seed Starting Calculator
Enter your last frost date and pick the crop. The calculator counts back the consensus weeks - peppers nine, tomatoes seven, cucumbers three - and gives the indoor sowing date, the transplant week, and days from today.
The seed packet is the boss; this table is the consensus window your variety and zone nudge. The two rules that separate thriving starts from leggy disappointment: light beats warmth once sprouted - a shop light an inch above the tray beats any windowsill - and transplant week is earned outdoors gradually, or the sun burns a month of care in one afternoon.
How to use
- Enter your area last frost date - extension tables have it for your town.
- Pick each crop; the weeks-before-frost are built in.
- Set a shop light an inch above the seedlings; windows stretch them.
Frequently asked questions
When should I start tomato seeds indoors?
Six to eight weeks before your last frost - seven is the sweet spot. Earlier is not better: tomatoes outgrow their trays and get leggy before the garden is ready, and leggy starts fruit less.
What happens if I start seeds too early?
Root-bound, light-starved transplants that wait weeks for the soil to warm - the head start evaporates. Peppers and tomatoes hold at a smaller size better than they recover from stretched stems.
Do I need grow lights to start seeds?
For anything beyond lettuce, effectively yes: a cheap shop light an inch above the seedlings for 14-16 hours beats the brightest windowsill, because winter sun is weak and low-angle - the legginess people blame on variety is usually window light.
What is hardening off?
The transplant-week discipline: an hour of outdoor shade the first day, doubling daily, until the starts survive full sun and breeze. Skipping it burns a month of indoor care in a single afternoon - the calculator schedules the week so it is not skipped.