USDA Zone 6a Planting Calendar (2026)
Zone 6a (-10 to -5°F) has an average last spring frost on Apr 20 and first fall frost on Oct 15 — about 178 growing days. Typical areas: St. Louis MO, Philadelphia PA.
How to use the zone 6a planting calendar
Every planting date on this page is calculated from zone 6a's average frost dates. Because your last spring frost lands around Apr 20 and your first fall frost around Oct 15, you have roughly 178 frost-free days to work with — a moderate growing season. The table below lists, for each of 20 common vegetables, when to start seeds indoors, when to sow or transplant outdoors, and when you can expect your first harvest.
Frost dates are averages, not guarantees. In a cold year the last frost can arrive 1-2 weeks later, so keep row covers handy for tender seedlings in Apr. Click any vegetable name to open a detailed zone 6a guide with spacing, companions, container tips and troubleshooting.
Cool-season crops for zone 6a
These tolerate light frost and go out first, 2-4 weeks before your Apr 20 last frost, and again in late summer for a fall crop: lettuce, carrot, broccoli, spinach, kale, onion, garlic, potato, peas, radish, beet, cabbage, cauliflower.
Warm-season crops for zone 6a
These need warm soil and frost-free weather, so plant them after Apr 20: tomato, pepper, cucumber, corn, bush beans, summer squash, zucchini. In a moderate season, start the slowest ones indoors to be sure they ripen before Oct.
| Vegetable | Start Indoors | Sow / Transplant | Harvest From |
|---|---|---|---|
| Beet | — | Mar 23 | May 17 |
| 🥦 Broccoli | Mar 16 | Apr 6 | Jun 10 |
| 🫘 Bush Beans | — | Apr 27 | Jun 21 |
| 🥬 Cabbage | Mar 9 | Apr 6 | Jun 25 |
| 🥕 Carrot | — | Mar 30 | Jun 8 |
| 🥦 Cauliflower | Mar 9 | Apr 6 | Jun 20 |
| 🌽 Corn | — | May 4 | Jul 23 |
| 🥒 Cucumber | Mar 30 | May 4 | Jun 28 |
| 🧄 Garlic | — | Oct 5 | Jun 2 |
| 🥬 Kale | Mar 16 | Mar 30 | May 24 |
| 🥬 Lettuce | Mar 23 | Mar 30 | May 14 |
| 🧅 Onion | Feb 9 | Mar 23 | Jul 1 |
| 🟢 Peas | — | Mar 9 | May 8 |
| 🫑 Pepper | Feb 23 | May 4 | Jul 13 |
| 🥔 Potato | — | Apr 6 | Jul 5 |
| 🌶️ Radish | — | Mar 23 | Apr 20 |
| 🍃 Spinach | — | Mar 16 | Apr 25 |
| 🎃 Summer Squash | Mar 30 | Apr 27 | Jun 16 |
| 🍅 Tomato | Mar 9 | Apr 27 | Jul 11 |
| 🥒 Zucchini | Mar 30 | Apr 27 | Jun 16 |
Spring, summer and fall planting in zone 6a
Spring (Apr): As soon as the soil can be worked, direct sow hardy cool-season crops and set out frost-tolerant transplants. This is your window for peas, lettuce, spinach and the brassicas before summer heat arrives.
Early summer (after Apr 20): Once frost danger passes and soil warms past 60°F, transplant tomatoes, peppers and squash and direct sow beans and cucumbers. This is the heart of the zone 6a growing season.
Late summer to fall (before Oct 15):Sow a second round of quick cool-season crops for a fall harvest. Count back each crop's days-to-harvest from Oct 15 to find the latest safe sowing date, and use row covers to stretch the season a few extra weeks.
Zone 6a planting FAQ
What planting zone is St. Louis MO?
Areas like St. Louis MO, Philadelphia PA fall in USDA hardiness zone 6a, defined by an average annual minimum temperature of -10 to -5°F. Your average last spring frost is around Apr 20 and your first fall frost around Oct 15.
When is the last frost in zone 6a?
The average last spring frost in zone 6a is around Apr 20. Wait until after this date before transplanting warm-season crops like tomatoes, peppers and squash. Cool-season crops can go out 2-4 weeks earlier because they tolerate light frost.
How long is the growing season in zone 6a?
Zone 6a has roughly 178 frost-free days between the last spring frost (Apr 20) and first fall frost (Oct 15). That is a moderate season — enough time for most vegetables plus some succession planting.
What vegetables grow best in zone 6a?
Reliable choices for zone 6a include cool-season crops such as lettuce, carrot, broccoli, spinach planted in early spring, and warm-season crops such as tomato, pepper, cucumber, corn planted after the last frost. See the full table below for exact dates.
Can I grow a fall garden in zone 6a?
Yes. With a first frost around Oct 15, you can plant a second round of quick cool-season crops in mid to late summer. Count back the days-to-harvest from Oct 15 to find your fall planting date.
When should I start seeds indoors in zone 6a?
Most warm-season seedlings are started indoors 6-8 weeks before the last frost — that means roughly Apr for zone 6a. Tomatoes, peppers and eggplant benefit most from an indoor head start in this zone.