Seed Starting Date Calculator
Get indoor seed-starting and outdoor transplant dates for common vegetables based on your last frost date and USDA zone. Runs in your browser.
Planting calendar
| Crop | Start indoors | Transplant / sow out |
|---|---|---|
| Tomato | Wed, Mar 4 | Wed, Apr 22 |
| Pepper | Wed, Feb 18 | Wed, Apr 29 |
| Eggplant | Wed, Feb 18 | Wed, Apr 29 |
| Broccoli | Wed, Mar 4 | Wed, Apr 1 |
| Cabbage | Wed, Mar 4 | Wed, Apr 1 |
| Lettuce | Wed, Mar 11 | Wed, Mar 25 |
| Onion (from seed) | Wed, Feb 4 | Wed, Apr 1 |
| Kale | Wed, Mar 4 | Wed, Mar 25 |
| Basil | Wed, Mar 4 | Wed, Apr 22 |
| Cucumber | Wed, Mar 25 | Wed, Apr 22 |
| Squash / zucchini | Wed, Mar 25 | Wed, Apr 22 |
Dates are computed from your last-frost date using extension planting-calendar norms (weeks before/after frost). The zone dropdown sets a rough average frost date — frost dates vary a lot within a zone, so enter your local average (from a frost-date lookup) for accuracy. Cool-season crops transplant before the frost date; warm-season crops after.
About this tool
Timing is everything when starting a vegetable garden from seed: sow too early and leggy seedlings outgrow their pots before it is warm enough to plant out; too late and the harvest runs out of season. Almost every planting schedule is anchored to one date — your average last spring frost — with each crop started indoors a set number of weeks before it and transplanted a set number of weeks before or after it. This calculator builds that calendar. Pick your USDA zone to load a rough average frost date (which you should refine to your local value), and it computes, for common crops, when to start seeds indoors and when to move them outside, using standard extension planting-calendar offsets. Warm-season crops like tomatoes, peppers, and basil go out after the frost date; cool-season crops like broccoli, cabbage, and lettuce can go out a few weeks before it. The essential caveat: frost dates vary widely even within a single zone due to elevation and microclimate, so enter your own local average for an accurate schedule. Everything is computed in your browser.
How to use it
- Select your USDA zone to load an approximate last-frost date.
- Replace it with your local average last-frost date for accuracy (look it up by ZIP/region).
- Read each crop's indoor-start and transplant/sow-out dates.
- Mark them on your calendar and start seeds accordingly.
Frequently asked questions
- How are the dates calculated?
- From your last frost date, using each crop's standard offset: start indoors a set number of weeks before the frost date, and transplant a set number of weeks before or after it. For example tomatoes start ~6 weeks before frost and transplant ~1 week after.
- Why is the last frost date so important?
- It is the reference point for the whole schedule. Tender crops are killed by frost, so they must go out after it; the indoor-start date is counted backward from it so seedlings are the right size at transplant time.
- Are the zone frost dates exact?
- No — they are rough averages. Frost dates vary substantially within a USDA zone because of elevation, proximity to water, and local microclimate. The zone sets a starting estimate; for accuracy, enter your own local average last-frost date.
- Which crops go out before the frost date?
- Cool-season, frost-tolerant crops — broccoli, cabbage, kale, lettuce, onions — can be transplanted a couple of weeks before the last frost. Warm-season crops (tomato, pepper, eggplant, basil, cucumber, squash) go out after it.
- What about a fall garden?
- This tool schedules around the spring last-frost date for a spring/summer garden. Fall plantings are timed backward from the first fall frost instead, using days-to-maturity — a different calculation not covered here.
- Is anything uploaded?
- No. The dates are computed entirely in your browser from the frost date you set.