USDA Zone 6a
Zone 6 · The Broad Middle
Average annual extreme minimum temperature: -10 to -5 °F (-23.3°C to -20.6°C).
Ohio, Missouri, the lower Midwest, and the milder Appalachians — −10 to 0°F winters and a season generous enough for two full plantings: the spring garden and the fall garden.
By the numbers
- Median last frost
- April 29
- Median first frost
- October 16
- Median season
- 172 days
- ZIPs tracked
- 4,574
Medians across every ZIP we track in zone 6a, derived from NOAA 1991–2020 climate normals. Look up your own ZIP for local dates — within a zone, frost varies by weeks.
Where you'll find zone 6
The 2023 map moved most of Ohio (95% of its ZIPs in our data are 6a or 6b) and the bulk of Missouri into zone 6, along with southern Pennsylvania valleys, the central Appalachians, and the lower Great Lakes fringe. Maritime Alaska reaches 6b at Seward — "the longest frost-free growing season in southern Alaska" (UAF).
Vegetables that earn their keep
- Long-season heat crops join the list: sweet potatoes, okra, watermelon, cantaloupe, large pumpkins (MU's Missouri roster)
- Tomatoes (Better Boy, Big Beef, Celebrity, Supersweet 100 — MU picks), peppers, eggplant, sweet corn
- Everything cool-season, twice: spring AND fall plantings of broccoli, lettuce, snap beans, spinach (MU calendar)
- Perennial vegetables: asparagus (Jersey types) and rhubarb (Canada Red)
Fruits & perennials that overwinter
- Peaches become realistic: Redhaven — "the most reliable cropping peach in Ohio" — plus very-hardy Reliance and Belle of Georgia (OSU)
- Hardiest nectarine: Mericrest (OSU)
- Disease-resistant apples: Liberty, Enterprise, Goldrush, William's Pride (OSU)
- All colder-zone fruit — tart cherries, raspberries, juneberries — remains easy
The two-season garden
Missouri Extension's planting calendar tells the zone-6 story in its structure: nearly every cool-season crop has two windows. Peas in March, lettuce in April — then snap beans again August 1–20, broccoli August 1–15, lettuce through August 30. The fall garden isn't a salvage operation here; it's a full second season, often with better quality than spring's.
Heat crops without the gamble
Sweet potatoes, okra, watermelon, and full-size pumpkins — marginal or impossible to the north — are standard recommendations in MU's variety lists. The frost-free season (our dataset's zone-6 median runs about 165–180 days) absorbs even 100-day heat-lovers with room to spare.
Stone fruit, and stone-fruit grief
Zone 6 is where peaches stop being a fantasy — and start being a heartbreak crop. Ohio State's warning: the crop is lost either to winter bud-kill or to late-spring frost at bloom. Their counsel is all about siting (high ground that cold air drains away from) and cultivar bud-hardiness (Redhaven, Reliance). Prune peaches in late winter only — fall pruning invites winter injury and canker (OSU).
Elevation rewrites the map
MU notes the Ozark Plateau uses the northern Missouri planting dates despite its southern latitude — elevation brings later spring and earlier fall frosts. The same logic applies through the Appalachians: in zone 6's hill country, your frost dates are a better guide than your latitude.
Plant guides, timed to your frost dates
Every guide gives its planting calendar relative to your last frost — the dates above (or your ZIP's) drop straight in.