Unlikely — Zone Mismatch
sunn hemp (zones 7-11) does not overlap with Wyoming's zone range (3b-6a). Growing outdoors is unlikely without significant protection.
One zone short — what would close it
Sunn Hemp is hardy to zone 7, and the warmest ground in Wyoming is zone 6 — 1 zone short. Planted in open ground it will not survive a Wyoming winter. To grow it here, grow sunn hemp in a container and move it under cover for the coldest weeks, or give it a greenhouse.
Season extension and overwintering under cover both work at this margin. How to buy the weeks →
Zone math from 7-11 (plant) against 3-6 (Wyoming). Lift modeled by crop_engine Sprint 20B effective_zone_modifier (+2 zones) via api/fast_sections.py Unlock Engine v2.
Your yard isn't the whole zone.
Sunn Hemp is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Wyoming site runs ~151 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score sunn hemp against your land's actual frost dates, sun, and soil.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Zone Comparison
Sunn Hemp Needs
- USDA Zones: 7-11
- Frost-Free Days: 60+
- Sun: Full Sun
- Mature size: 6 ft tall
- Picking window: ~30 days of harvest
- Drought tolerance: Medium
Wyoming Has
- USDA Zones: 3b-6a
- Last Hard Freeze (28°F): May 4 - May 13
- First Hard Freeze (28°F): Sep 30 - Oct 7
- Annual Rainfall: 6-20 inches
- Common Soils: Sandy loam, Clay, Alkaline
Plant Zone Range (zones 7-11)
Preferred Soil pH
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Sunn Hemp in Wyoming
The frost window
Across Wyoming, the last spring hard freeze (28°F) clears between May 4 and May 13, and the first fall hard freeze lands between Sep 30 and Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 140-day window you can count on — up to 156 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
Frost tenderness
Sunn Hemp is frost-tender — its listed minimum temperature is 39.2°F (USDA PLANTS Database) — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does.
When to start the seed
Sunn Hemp is direct-sown where it grows rather than started under cover, so there is no seed-tray head start to bank — Wyoming's dates above are the whole calendar for it. That makes the last-freeze date the binding constraint, and a warmer pocket of your own yard is worth more to this crop than it is to a transplanted one.
Days to maturity vs. the window
At 90 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 50 days to spare even in Wyoming's tightest freeze scenario — room for a later start or a second sowing.
Timing tuned to sub-state frost dates — Teton County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: USDA PLANTS Database. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says sunn hemp does not survive a Wyoming winter in the ground. The season figures below measure a different question — whether it could finish a season here at all — and they only bear on Wyoming under protection.
Frost-free days
Sunn Hemp wants 60+ frost-free days; a typical Wyoming site sees ~151 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Sunn Hemp needs ~2200 GDD (base 50°F) to ripen. The state median runs ~1866 GDD (from PRISM 1991-2020 climate normals), so Wyoming's typical season runs short on heat — pick a south-facing site and consider season extension.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Sunn Hemp tolerates a wide pH range (pH 5-8.4) — 3.4 units, acid ground through alkaline — so soil acidity is rarely what limits it in Wyoming. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 6 and 7 — worth knowing before you decide whether a Wyoming soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Wyoming site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Wyoming's soils run mostly loam, but SSURGO maps the series, texture, and drainage under your exact parcel. Sunn Hemp needs about 19 inches of workable depth, so it is that horizon — not the surface — you are testing for. That map unit, not the state average, decides how sunn hemp performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Wyoming soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Sunn Hemp in Wyoming — Quick Answer
- Verdict: Unlikely — Zone Mismatch
- Plant Zones: 7-11 (USDA PLANTS Database)
- State Zones: 3b-6a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about May 4 - May 13 to Sep 30 - Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 90 days
What Else to Consider for Sunn Hemp in Wyoming
Zone compatibility tells you about winter cold survival — but Wyoming growers also need to think about:
Extremely short growing season (60-90 frost-free days)
Very low rainfall requires irrigation
Persistent high winds desiccate and damage plants
Growing sunn hemp here specifically
Sunn Hemp's medium root system wants open ground, yet a large share of Wyoming is SSURGO group-D soil — dense and slow-draining enough to stall it.
Double-dig or broadfork sunn hemp's bed to open the restrictive layer so roots can run. How to handle it →
What to actually do about these — and the constraints that apply to every Wyoming grower, not just sunn hemp — is covered on the Wyoming growing guide.
Timing shifts within Wyoming
Wyoming isn't one climate. In Teton County, the last hard freeze (28°F) holds until about Jun 16 — roughly 41 days later than the recorded state median — so plant sunn hemp to your county's window, not the statewide date.
Sunn Hemp needs about 60 days of frost-free season to complete its cycle. Even Teton County — Wyoming’s shortest season at 79 frost-free days — clears that by 19 days, so season length isn’t the constraint anywhere in Wyoming. What varies is your own parcel.
Across Wyoming’s 23 counties the frost-free season runs from 79 days in Teton County to 166 days in Big Horn County — a spread of 87 days, which is why a single statewide planting date misleads. The median Wyoming county sees 151 frost-free days, leaving sunn hemp about 91 days of slack on a typical parcel — room for a second sowing where the season runs long.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Sunn Hemp's 60-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Sunn Hemp draws honeybees, native bees, and butterflies (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, sunn hemp can only work that bloom inside Wyoming's frost window — roughly 151 days, opening after the last 28°F freeze (May 4 - May 13) and closing at the first (Sep 30 - Oct 7), per NOAA Regional Climate Centers ACIS, 1991-2020.
Good to Know Before You Plant Sunn Hemp
Sunn Hemp is listed as toxic to dogs, cats (seeds) at a moderate level (Cornell). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear. Worth knowing for placement: in Wyoming this is a one-season plant and the first hard freeze (Sep 30 - Oct 7) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Wyoming Cooperative Extension
For Wyoming-specific cultivar recommendations, planting calendars, and pest pressure for sunn hemp, the canonical source is University of Wyoming Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Sunn Hemp native to Wyoming?
No — the USDA PLANTS Database lists Sunn Hemp as introduced rather than native in the Lower 48, so it is not part of Wyoming's native flora. It grows here as a garden plant; pairing it with a few Wyoming natives keeps local pollinators fed too.
Looking for plants that belong here? The Wyoming growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Sunn Hemp in Wyoming
When can I plant Sunn Hemp in Wyoming?
Wyoming's last spring hard freeze (28°F) clears between May 4 and May 13, and the first fall hard freeze lands between Sep 30 and Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020). Sunn Hemp is frost-tender — its listed minimum temperature is 39.2°F (USDA PLANTS Database) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can Sunn Hemp mature before first frost in Wyoming?
Yes — Sunn Hemp matures in 90 days (USDA PLANTS Database), and Wyoming's dependable hard-freeze-free window runs 140 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 50 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Sunn Hemp grown in across Wyoming?
Wyoming spans USDA hardiness zones 3b-6a (USDA ARS PHZM 2023). Sunn Hemp carries a range of zones 7-11, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Wyoming site have?
A typical Wyoming site sees ~151 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Sunn Hemp needs 60+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Teton, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Sunn Hemp native to Wyoming?
No — the USDA PLANTS Database lists Sunn Hemp as introduced rather than native in the Lower 48, so it is not part of Wyoming's native flora. It grows here as a garden plant; pairing it with a few Wyoming natives keeps local pollinators fed too.
How should I amend the soil for Sunn Hemp in Wyoming?
Sunn Hemp tolerates pH 5-8.4 and well (dry spells) drainage (FAO ECOCROP). That is a 3.4-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Wyoming site — amend for drainage and organic matter first.
Will Sunn Hemp actually grow on my specific land in Wyoming?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores sunn hemp against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Wyoming
State-level data is a sketch. Your Growable Ground report scores sunn hemp against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Wyoming sunn hemp averages can't show:
We read public map data around Wyoming — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Wyoming sunn hemp average
Explore More
Growing guides for sunn hemp
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
Last updated: