What is the last frost date?

It is the average date of the last spring frost in your area — after which the risk of a killing frost is low. Tender crops planted outdoors before this date can be damaged. It is a statistical average, not a guarantee, so a late cold snap is always possible. Check your local agricultural extension or weather service for your specific date.

How does the calculator decide sow dates?

Each crop has a recommended number of weeks to start seeds indoors before the last frost — tomatoes around 6-8 weeks, peppers 8 weeks, lettuce 4 weeks. The tool subtracts that many weeks from your frost date to give the indoor sow date, and uses each crop's transplant timing to set when seedlings can safely go outside.

Why do some crops transplant before the frost date and others after?

Cool-season crops such as lettuce, broccoli and onions tolerate light frost and can go out a couple of weeks before the last frost. Warm-season crops like tomatoes, peppers and cucumbers are frost-tender and must wait until after the last frost, sometimes a week or two later when the soil has warmed.

Should I direct-sow instead of starting indoors?

Some crops resent transplanting and do best sown directly where they will grow — carrots, beans, peas, radishes and most root vegetables. The calculator focuses on crops commonly started indoors. For direct-sown crops, use the listed transplant-equivalent date as your outdoor sowing date.

How accurate is this for my exact garden?

It uses widely published weeks-before-frost guidance, which is a sound starting point, but microclimates vary. A sheltered south-facing bed warms earlier than an exposed plot. Treat the dates as a planning baseline, watch the actual weather, and harden off seedlings before transplanting regardless of the calendar.

Frost Date Planting Schedule Calculator

The Frost Date Planting Schedule Calculator turns a single piece of information — your average last spring frost date — into a complete seed-starting and transplanting calendar for the crops you want to grow. It is built for home gardeners who know roughly when their frosts end but are unsure when to start each vegetable indoors.

How it works

Seed-starting is all about counting backwards from the last frost. Each crop has a well-established weeks-before-frost window for sowing indoors, and a transplant offset that says how many weeks before or after the last frost the seedlings can safely go outside:

indoor sow date   = last frost date − (weeks before frost)
transplant date   = last frost date + (transplant offset)

A negative transplant offset means the crop is frost-hardy and goes out before the last frost; a positive offset means it is tender and must wait after it. The calculator applies each crop’s built-in figures and sorts the schedule so you know what to sow first.

The data table covers common crops, for example:

Tomatoes  — start 6 weeks before frost, transplant 1 week after
Peppers   — start 8 weeks before, transplant 2 weeks after
Lettuce   — start 4 weeks before, transplant 2 weeks before
Broccoli  — start 6 weeks before, transplant 2 weeks before
Onions    — start 10 weeks before, transplant 2 weeks before

Tips and notes

Find your frost date first. Local extension services and national weather offices publish average last-frost dates by location. A rough date is fine for planning.
Harden off seedlings over 7-10 days before transplanting — gradually exposing them to outdoor conditions — regardless of what the calendar says.
Cool-season crops go out early; warm-season crops wait until the soil warms. The transplant dates reflect this automatically.
The dates are a planning baseline, not a forecast. Watch the actual weather near your transplant dates and delay if a late cold snap threatens.