Gardening in Wyoming

Hardiness zones in Wyoming

Wyoming's USDA hardiness zones range from 4a to 5b. A hardiness zone marks the average coldest night your area sees each winter, nothing more. Zone 4a winters get colder than zone 5b winters, so a plant rated for zone 5 may struggle in a 4a spot. The zone number says nothing about summer heat, rainfall, or soil. Two gardens in the same zone can still need different care for those reasons. This page's zone data for Wyoming comes from readings at 111 weather stations across the state. That is why the range spans four bands, from 4a and 4b up through 5a and 5b. Check your own zone against a plant's rating rather than relying on the state's full range.

• Zone 4a
• Zone 4b
• Zone 5a
• Zone 5b

Frost dates

Frost dates mark the typical start and end of the growing season in a given spot. Across Wyoming, the last spring frost falls as early as April 28 in some spots and as late as June 24 in others. The first fall frost arrives as early as August 28 in the coldest spots and as late as October 10 elsewhere. Those dates come from a 50% chance of frost, meaning a frost is about as likely as not on that date. Wait until after your area's last frost date before moving tender plants outdoors. Bring tender plants in, or protect them, once your first fall frost date approaches. Between those two dates sits the growing season, and it varies widely across the state. The shortest growing season recorded is just 19 days, while the longest reaches 164 days. That gap shows how much frost timing can differ between one part of Wyoming and another.

Climate

Across the state, 111 weather stations feed the climate data used on this page. Those stations show a hardiness range of zone 4a up to zone 5b, so winter lows vary by location. The coldest areas sit at zone 4a, while the mildest reach zone 5b. Frost timing varies just as much as winter cold does. The last spring frost can land anywhere from April 28 to June 24 depending on where you are. The first fall frost can arrive from August 28 to October 10. Those two ranges combine to produce growing seasons from 19 days at the short end to 164 days at the long end. A 19-day season and a 164-day season call for very different plant choices, even within one state. This page does not cover summer heat, rainfall, or soil, since the data behind it tracks only frost and hardiness zone. Use your own location's zone and frost dates, not a statewide average, when you plan what to plant and when.

Season length

Growing season length in Wyoming depends heavily on where you garden. Some spots in the state see a growing season of just 19 days between frosts. Other spots see a season stretching to 164 days. That is a big gap between the shortest season and the longest one recorded. If you garden in a short-season area, choose fast-maturing crops and consider starting seeds indoors before your last frost date. If your season runs longer, you have more room to grow crops that need extra weeks to mature. Either way, check your own local frost dates rather than assuming the statewide range applies to your yard.