This is the master chart we use, based on the Farmers' Almanac seed-starting guide and university extension timing. Tape it inside a cupboard door; it doesn't expire.
First, find your two dates
Your garden runs on two dates:
- Last spring frost — the average date after which freezing nights stop. Everything in this article counts from it.
- First fall frost — the average date freezing nights return (that one runs the fall garden).
Look both up by ZIP code with the Old Farmer's Almanac frost-date tool — it's free and based on 30-year climate normals from U.S. weather stations. Write the dates on the chart and you're done with research forever (or until you move).
A quick honesty note: frost dates are averages, not guarantees. Roughly speaking there's still about a one-in-three chance of a frost after the "last frost date," which is why tender crops wait a week or two past it. Weather forecasts get the final vote.
Frost date vs. USDA zone — they're different tools
This trips up almost everyone, so let's untangle it:
- Your USDA hardiness zone (from the 2023 map at planthardiness.ars.usda.gov) describes your average coldest winter night. It answers: will this rosebush survive winter here? It says nothing directly about frost timing.
- Your frost dates describe when freezing nights end and begin. They answer: when do I plant the lettuce?
Two towns can share a zone but differ by weeks in frost dates (coastal vs. inland, valley vs. hilltop). Use the zone for buying perennials, shrubs, and bulbs; use frost dates for scheduling the vegetable garden. For vegetables, the frost date does the work.
The chart: weeks before and after last spring frost
Direct-sow seeds outdoors:
| When (vs. last spring frost) | Sow these outdoors |
|---|---|
| 4–6 weeks before | Peas, spinach, leaf lettuce, radishes, kale, arugula, mustard & Asian greens, turnips, onion sets |
| 2–4 weeks before | Beets, carrots, Swiss chard, potatoes (seed pieces), kohlrabi |
| At last frost, soil warming | Bush & pole beans, sweet corn, cucumbers, summer squash |
| 1–2 weeks after (soil warm) | Melons and winter squash from seed; basil; okra; sweet potato slips |
Transplants (started indoors or bought as plants):
| Crop | Start seeds indoors | Set plants outside |
|---|---|---|
| Broccoli, cabbage, cauliflower | 4–6 weeks before last frost | 2–4 weeks before last frost |
| Lettuce (heads) | 4–6 weeks before | Around last frost |
| Tomatoes | 6–8 weeks before | 1–2 weeks after last frost |
| Peppers, eggplant | About 8 weeks before | 2 weeks after, once nights stay above ~55°F |
The pattern behind the whole table: the cabbage-and-lettuce crowd likes cool soil and shrugs off frost, so it goes early. The tomato-and-squash crowd is killed by one freezing night and sulks in cold soil, so it waits until the danger has clearly passed.
A worked example
Say your last frost is May 5 (common across zone 6):
- Peas and spinach: 4–6 weeks before → sow March 24 – April 7
- Carrots and beets: 2–4 weeks before → sow April 7–21
- Tomato seeds indoors: 6–8 weeks before → start March 10–24
- Beans and corn: at frost date → sow around May 5
- Tomato plants outside: 1–2 weeks after → plant May 12–19
Five dates, one anchor. That's the entire system.
Two refinements worth knowing
Soil temperature is the tiebreaker. Dates get you close; the soil gets the final say, especially in a cold, wet spring. Seeds rot in soil that's too cold: peas want about 45°F and up, beans about 60°F, squash and melons 65–70°F. An inexpensive soil thermometer settles arguments the calendar can't. (Raised beds and containers warm earlier than open ground — one more reason we like them; see our raised bed guide.)
Frost isn't freeze. A light frost (around 29–32°F) whitens the lawn and takes out basil and tomatoes, but leaves lettuce, peas, and the cabbage family unbothered. A hard freeze (below about 28°F) ends the season for all but the toughest crops, per Iowa State Extension's hardiness groupings. Knowing the difference saves a lot of unnecessary panic — and a few salvageable salads.
The same trick runs your fall garden
Count backward from your first fall frost — days to maturity, plus a harvest window, plus a couple of "fall factor" weeks for slower autumn growth — and you know the last sowing date for any crop. We walk through that math, zone by zone, in what to plant in August, and the Planner Kit includes a worksheet page that does the counting for you.
Find your zone's calendar
Prefer the whole year laid out for your zone, month by month? We're building a calendar page for every USDA zone, starting with the most-gardened one:
- Zone 6 Planting Calendar: What to Plant, Month by Month
- Zone 7 Planting Calendar: What to Plant, Month by Month
- Zone 5 is next — check back soon.
This chart, on your fridge
The free Printable Garden Planner Kit includes this planting chart in large print, frost-date tables for zones 3–10, and a fill-in calendar — made to be penciled on, not squinted at.
Frequently asked questions
How accurate are frost dates?
They're 30-year averages, so treat them as a bell curve, not a fence. There's still roughly a 30% chance of frost after your average last-frost date. Cold-hardy crops don't care; for tomatoes and peppers, wait the extra week or two and watch the 10-day forecast.
What if a surprise frost is forecast after I've planted?
Cover tender plants overnight with an old bed sheet, upside-down buckets, or milk jugs with the bottoms cut out — on before dusk, off in the morning once it's above freezing. Hardy crops (peas, lettuce, brassicas, onions) can be left alone.
Is my USDA zone the same as my frost date?
No. The zone measures average winter minimum temperature (for choosing perennials); frost dates measure when freezing nights end and return (for scheduling annual vegetables). You need your ZIP-code frost dates, not just your zone number, to use planting charts properly.
When should I start seeds indoors?
Work backward from the transplant date, not the frost date itself: tomatoes need 6–8 weeks on the windowsill before going out 1–2 weeks after frost; peppers need about 8; broccoli and cabbage need 4–6 weeks before their early planting. Starting too soon makes leggy, root-bound plants — later is safer than earlier.
Do raised beds and containers change the dates?
A little, in your favor. The soil in them drains and warms 1–2 weeks earlier than open ground in spring, so early sowings (peas, lettuce, radishes) can often nudge forward. Frost dates themselves don't move — air is air — so tender crops keep their schedule.