When to start seeds in a cold-climate zone

Count back six weeks from your last frost date, not from when you feel like starting. Ten weeks under lights gets you a rootbound, stressed plant that spends its first month outdoors recovering instead of growing.

Find your last frost date

Your local extension office publishes this by zip code, and it's more reliable than a general zone chart. In zone 5b upstate, ours lands in mid-May most years. We start seeds the first week of March.

Why earlier isn't better

A six-week-old seedling transplants cleanly into a final container and resumes growth within days. A ten-week-old seedling has usually outgrown its indoor pot, developed circling roots, and needs a week or more just to recover from the transplant before it starts vegging in earnest. In a season this short, that week matters.

What we do differently now

We used to start in mid-February out of impatience. Moving the date back to early March cost us nothing in final plant size and saved two weeks of babysitting leggy, light-starved seedlings indoors.