What Grows in Mammoth, Wyoming

Mammoth sits in USDA hardiness zones 4a-5b, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.

For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Apr 20; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 18 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 28 — long-season crops need about 90 days of runway, quick greens only 30. When the window is tight, the fall moves are quick ones — baby greens, radishes, and garlic set for next season.

The last hard freeze (28°F) in Mammoth typically lands around May 18, per NOAA 1991–2020 climate normals — an earlier marker than the light-frost dates many planting charts quote. That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.

The first hard freeze (28°F) in Mammoth typically arrives around Sep 28, per NOAA 1991–2020 climate normals — the point most tender summer crops finish. Lighter frosts usually reach a couple of weeks earlier, so watch the forecast from late summer on and harvest or cover tender plants before the first cold night.

Mammoth's zones 4a-5b support a wide range — strong performers include Potato, Indian Paintbrush, Cottonwood, Rhubarb, and Chokecherry. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.

Officially, Mammoth sits in USDA zones 4a-5b (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.

The federal record around Mammoth runs heavier than most — 52 documented sites — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.

With about 133 frost-free days between hard freezes, Mammoth rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder, cold frames and low tunnels more, and quick-maturing varieties make the arithmetic work. Starting transplants indoors ahead of the May 18 hard-freeze normal stretches the season without touching the calendar.