Wyoming Planting Guide: What to Grow and When in Zones 3–5

Wyoming will humble any gardener who ignores its rules—and reward any gardener who learns them. With growing seasons ranging from 79 days in the Tetons to 171 days in the Big Horn Basin, with hard frosts possible in every month at high elevation, and with soil that typically lacks organic matter, this is not a state for generic advice. But gardeners across Wyoming grow excellent vegetables, stunning native perennials, and productive fruit beds every year. The difference between a dead garden and a thriving one comes down to three things: knowing your zone, respecting your frost dates, and choosing varieties built for short seasons.

This guide uses University of Wyoming Extension research and NOAA climate data to give you a calendar and plant list built specifically for Wyoming conditions. No fluff—just what works, when to do it, and why.

Understanding Wyoming’s USDA Hardiness Zones

Wyoming spans USDA hardiness zones 3b through 6a on the 2023 updated map, though most gardeners live and plant in zones 3b through 5a. Your zone tells you the average annual minimum winter temperature—useful for choosing perennials that will survive winter, but less useful for timing annual crops (that’s where frost dates come in).

Here’s how zones break down across the state:

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• Zones 3b–4b (most of the state): Extreme southwest Wyoming, the high plains, and mountain communities. Minimum winter lows reach −30°F to −10°F. Cold-hardy crops, native perennials, and short-season varieties are your foundation.
• Zone 5a (Cheyenne, Casper, lower-elevation eastern Wyoming): Minimum lows of −15°F to −10°F. More variety options open up, including some warm-season crops with season extension tools.
• Zones 5b–6a (southwestern pockets: Lincoln, Uinta, Sweetwater counties): The mildest parts of Wyoming. Tomatoes, peppers, and cucumbers grow more reliably here. Still not forgiving—but the window is wider.

One important note: USDA zones are shifting northward and upward as climate patterns change. If you’re in a borderline area, check the 2023 map rather than relying on older zone references—some Wyoming locations moved half a zone warmer.

Frost Dates and Growing Season by City

Frost dates matter more than zones for annual vegetables. Wyoming’s variation by city is dramatic—Laramie gardeners have less than 100 frost-free days while Basin gardeners enjoy nearly 6 months. Plan your entire calendar around your city’s last spring frost date, not a state average.

The table below uses NOAA Climate Normals data (30% probability—meaning there’s a 30% chance frost could occur outside these dates, so always keep row covers handy through late spring).

Two things stand out. First, Laramie’s last frost is nearly six weeks later than Basin’s—that’s the difference between a full warm-season growing window and a cool-season-only garden. Second, Laramie’s first fall frost (August 29) is shockingly early. A tomato transplanted there after its last frost date has roughly 75 frost-free days—only enough for varieties with a days-to-maturity (DTM) under 70.

If your city isn’t in this table, the NOAA-based tool at plantingzonesbyzipcode.com lists frost dates for over 200 Wyoming cities and towns.

How Elevation Changes Everything

Frost dates are one thing. Elevation adds a second layer that most general gardening guides miss entirely.

The University of Wyoming Extension’s Growing Vegetables in Wyoming (Pub B-1115R) draws a clear line at 6,500 feet: above this elevation, cucumbers, eggplant, muskmelons, okra, winter squash, peppers, tomatoes, and watermelons are not recommended. This isn’t pessimism—it’s soil temperature biology. Tomato roots stop absorbing nutrients efficiently below 60°F. At 6,500+ feet, soil temperatures at root depth often stay below that threshold even on warm-air days, producing stunted plants that never catch up before October frost returns.

Where does this put Wyoming’s major cities?

• Cheyenne (6,063 ft): Just below the cutoff. Warm-season crops work with season extension tools and south-facing placement.
• Casper (5,150 ft): Well below 6,500 ft. One of Wyoming’s better environments for warm-season crops.
• Laramie (7,165 ft): Above the cutoff. Focus entirely on cool-season crops. Tomatoes and peppers are a stretch even with Wall-o-Waters— select the fastest short-season varieties and expect unreliable results.
• Jackson Hole (~6,200 ft): Borderline. The 79-day growing season and marginal soil temps make warm-season crops high-risk. Stick to cool-season crops and native perennials.

The practical takeaway: if you’re above 6,500 feet, treat tomatoes as a bonus crop rather than a staple—and build your garden around what consistently succeeds: salad greens, root vegetables, brassicas, peas, and cold-hardy perennials.

Wyoming Month-by-Month Planting Calendar

The calendar below is anchored to the Casper/Cheyenne timeframe (last frost: mid-to-late May). If you’re in Laramie or high-altitude areas, push every “outdoors” date forward by 3–4 weeks. If you’re in Basin, you can pull cool-season outdoor dates back 2–3 weeks earlier.

March – Indoor Seed Starting Begins

March is the time to start warm-season crops indoors—not plant them outside. Tomatoes and peppers need 6–8 weeks of indoor growth before transplanting, which means early-to-mid March for a late-May outdoor date. For Laramie and mountain areas, start 8 weeks before your last frost date (typically early April, given a mid-June last frost).

• Start indoors: tomatoes, peppers, eggplant (at or below 6,500 ft only), celery, onion seed
• Start indoors (late March): broccoli, cauliflower, cabbage (4–6 weeks before transplanting)
• Test your garden soil before adding any fertilizer or organic matter—Wyoming soils vary widely in pH and salt content, and testing first prevents over-application

April – Soil Preparation and Early Season Setup

• Incorporate 2–3 inches of well-composted organic matter into garden beds—Wyoming’s native soils typically lack it
• Dormant-prune trees, vines, and brambles before buds break
• Direct-seed cold-tolerant crops outdoors only after soil is workable and temperatures are consistently above freezing: this may be late April in Basin and Casper, but not until May in Cheyenne and not until late May in Laramie
• Plant asparagus and rhubarb crowns as soon as soil is workable—both are perennials that tolerate light frost
• Harden off seedlings started in March by gradually exposing them to outdoor conditions

May – Cool-Season Crops Go In

May is the most active planting month for most Wyoming locations. Work from your specific last frost date backward and forward:

• 4 weeks before last frost: Transplant broccoli, cauliflower, cabbage seedlings
• 2–4 weeks before last frost: Direct-seed beets, carrots, spinach, lettuce
• ~May 1 (Casper/Cheyenne): Plant early-variety potatoes
• 1–2 weeks before last frost: Direct-seed peas; they germinate in cool soil and tolerate light frost
• Establish raspberry and strawberry plants; plant asparagus crowns if not done in April
• Succession-plant lettuce and spinach every 2–3 weeks for a continuous harvest through July

Do not rush warm-season transplants outdoors in May. A tomato set out before last frost and hit by 28°F will suffer cold injury that sets it back 2–3 weeks—erasing any time advantage you gained by planting early.

June – Warm-Season Planting Window Opens (Low Elevations)

After your last frost date—mid-to-late May for Cheyenne and Casper, mid-June for Laramie—the warm-season window opens:

• Transplant tomatoes and peppers. Use Wall-o-Waters or clear plastic tunnels for extra warmth and protection
• Direct-seed beans (bush and pole) and sweet corn only after last frost—these don’t tolerate even light frost
• Direct-seed only (do not transplant): cucumbers, zucchini, summer squash, pumpkins, melons. These crops don’t recover well from root disturbance at transplanting. Sow 2–3 seeds per hill and thin to the strongest plant.
• Apply 2–3 inches of mulch in mid-June, after the soil has warmed. Mulching too early keeps cold soil cold—exactly what you don’t want in Wyoming’s short season
• Plant warm-season annuals (marigolds, zinnias, nasturtiums) after last frost

July – Peak Season and Fall Planting Setup

• July 1–15: Plant a second crop of peas in areas with enough season remaining. In Cheyenne (frost returns late September), a July 10 planting of a 60-day pea variety will finish September 8—just in time
• Plant fall radishes and turnips (late July); these mature in 22–70 days and improve with cool fall temperatures
• Deadhead flowering perennials and annuals regularly to extend bloom season
• Monitor for common Wyoming pests: aphids on brassicas, squash vine borers, spider mites in dry conditions
• Maintain 1.5 inches of water per week as crops near maturity; Wyoming’s arid climate and persistent wind accelerate soil moisture loss

August – Race to the Finish Line

August is a critical month, especially at higher elevations. Laramie’s first fall frost can arrive as early as August 29—which means August is effectively the beginning of fall for Laramie gardeners.

• Check DTM on all warm-season crops and count days to first fall frost. Anything that won’t mature in time should be harvested immature (green tomatoes ripen indoors; squash cures) rather than left to be killed by frost
• Plant a final round of fast-maturing cool-season crops: spinach (40–48 days), radishes (22–35 days), arugula, and leaf lettuce will finish before hard freeze in most locations
• Install frost protection materials—row covers, cold frames—before you need them. Wyoming weather moves fast
• Harvest garlic (if planted last fall) once lower leaves brown

September – Harvest and Winterize

• First frosts arrive: late September in Cheyenne and Casper, potentially mid-September or earlier at altitude
• Harvest warm-season crops before hard freeze (28°F or below for 4+ hours). Light frosts (30–32°F) can be protected with row covers
• Plant spring-blooming bulbs (tulips, daffodils, crocuses) in September–early October—they need 12–16 weeks of cold to bloom
• Plant garlic cloves for harvest next summer; this is one of the most reliable Wyoming crops
• Divide and transplant hardy perennials after temperatures cool

October – February: Planning Season

• After killing frost, cut back perennials and mulch tender root zones with 3–4 inches of straw or shredded leaves
• Order seed catalogs from companies specializing in short-season and northern varieties (Johnny’s Selected Seeds, High Mowing, Territorial Seed)
• Complete dormant pruning of fruit trees and vines in February before growth begins
• Review your frost date notes from this season and adjust next year’s calendar accordingly

The Best Vegetables for Wyoming Gardens

The most successful Wyoming vegetable gardens share one trait: they’re built around crops whose days-to-maturity (DTM) fit comfortably inside the local growing season, with at least a 2-week buffer before first fall frost. University of Wyoming Extension recommends choosing varieties developed for the northern US and Canada, where short seasons shaped the breeding.

LF = last frost date. DTM = days to maturity. For tomatoes, look for varieties labeled “early” or “short-season”: Siletz, Glacier, Sub-Arctic Plenty, Legend, and Bush Early Girl are proven performers in mountain-West gardens.

For a deeper look at pairing vegetables that help each other, see our companion planting guide—interplanting radishes with slow-maturing carrots, for example, is a smart Wyoming strategy that uses garden space efficiently through the short season.

Flowers and Perennials That Thrive in Wyoming

Wyoming’s native plants evolved in conditions most garden plants would find intolerable: alkaline soil, semi-arid precipitation, extreme cold, and persistent wind. Starting with natives or cold-hardy adapted perennials means planting once and enjoying for decades.

Native Wildflowers and Perennials

Pasque flower (Pulsatilla patens) is often Wyoming’s earliest garden color—blooming in March and April when snow is still possible, from furry buds that push through frozen ground. It’s reliably zone 3, thrives in rocky soil, and needs almost no supplemental water after establishment. If you want one plant that defines Wyoming gardening, this is it.

Blanket flower (Gaillardia) earns its place as the longest-blooming perennial in Wyoming gardens, flowering from June through hard frost in shades of red, orange, and yellow. Drought-tolerant and zone 3 hardy, it self-seeds reliably without becoming invasive.

Native butterfly weed (Asclepias tuberosa) serves double duty as an ornamental and a monarch butterfly larval host plant. It blooms orange in June through August, grows to 2 feet, and is both deer-resistant and drought-tolerant once established.

For annual color, plant marigolds, cosmos, and nasturtiums after last frost—all three are fast-maturing and perform reliably in Wyoming’s short warm season. Nasturtiums double as a companion planting tool, deterring aphids from nearby brassicas.

Season Extension: Getting More From Wyoming’s Short Window

Season extension isn’t optional in Wyoming—it’s how you grow tomatoes in Cheyenne and salad greens in October. The University of Wyoming Extension offers dedicated publications on both high tunnels (Pub B-1234) and cold frames/hotbeds (Pub B-1151R), and the technology has only improved since those guides were written.

Row Covers

Lightweight floating row cover (1.0–1.5 oz/sq yd) adds 4–6°F of frost protection with no light reduction. It’s the cheapest, most versatile tool Wyoming gardeners have. Keep rolls of it available through May and again from mid-August onward. A surprise frost on May 25 in Cheyenne is survivable if you have row cover on hand; it’s devastating if you don’t.

Wall-o-Waters and Water-Filled Protectors

Circular tubes filled with water absorb daytime heat and release it overnight, creating a microclimate warm enough to protect tomatoes down to around 16°F. UW Extension describes this approach using “circular plastic tubes filled with water” as a method for protecting individual plants in early season. In practice, Wall-o-Waters allow Wyoming gardeners to transplant tomatoes 4–6 weeks before their official last frost date—turning a 100-day growing season into a 130+ day effective window for that single crop.

Cold Frames

A cold frame—a bottomless box with a clear lid, positioned facing south—extends both the spring and fall seasons by 4–6 weeks. In spring, you can start cool-season greens in a cold frame 6–8 weeks before outdoor direct sowing is possible. In fall, keep harvesting spinach and kale in a cold frame through October and into November in lower-elevation Wyoming locations.

Raised Beds

Raised beds warm 2–3 weeks faster than in-ground soil in spring—critical in a state where every week of growing season matters. Line the outside of raised beds with dark-colored materials or use black plastic mulch inside to maximize solar heat absorption early in the season.

Soil, Water, and Wind: Wyoming’s Three Garden Variables

Soil

Wyoming’s native soils typically lack organic matter. Many areas also have heavy clay that compacts easily or alkaline pH from calcium carbonate deposits. Before your first season, incorporate 3–4 inches of well-composted organic matter into the top 12 inches of soil. This improves drainage in clay, improves water retention in sandy soils, and lowers pH slightly in alkaline areas. A soil test from your local UW Extension office gives you a baseline so you’re not guessing on amendments. Contact the UW Extension at barnyardsbackyards@uwyo.edu or (307) 766-5124 for local guidance and testing resources.

Apply 2–3 inches of mulch—straw, shredded leaves, or wood chip—in mid-June, after the soil has warmed. Mulching before the soil is warm extends the cold period at root depth, which slows germination and early growth. Once soil temperatures are consistently above 60°F, mulch becomes invaluable for moisture retention.

Water

Most vegetables require at least 1.5 inches of water per week as they approach maturity, applied deeply enough to moisten the soil to 6–8 inches. Wyoming’s semi-arid climate means rainfall rarely meets this threshold during summer, and drip irrigation or soaker hoses deliver water most efficiently—directly to the root zone with minimal evaporation. Overhead irrigation in the late afternoon or evening, combined with warm humid nights, can promote fungal disease; morning watering is better.

For a broader view of how water availability and climate are reshaping what’s possible in Wyoming and neighboring states, our guide on year-round planting covers how to plan a continuous harvest calendar that adapts to changing conditions.

Wind

Wyoming is one of the windiest states in the country—and persistent wind is one of the least-discussed garden challenges. Wind desiccates soil and plant tissue faster than arid conditions alone, and it physically damages tall plants like corn and tomatoes that haven’t been staked.

Karen Panter, University of Wyoming Extension horticulture specialist, recommends positioning windbreaks—fences, hedgerows, or dense shrubs—at a distance downwind equal to 10 times the windbreak’s height. A 5-foot fence protects a 50-foot corridor of garden. A 6-foot solid fence or dense hedge protects 60 feet. Position your garden beds within that protected corridor, not beyond it. Without a windbreak, plan on watering 20–30% more frequently and staking every upright plant.

Frequently Asked Questions

Can I grow tomatoes in Wyoming? Yes, at elevations below 6,500 feet, with short-season varieties (50–65 DTM) and season extension tools. Casper and Cheyenne gardeners have the best odds. Above 6,500 feet (Laramie, Jackson), tomatoes are high-risk and rarely productive without high tunnels.

When is the last frost in Cheyenne and Casper? Cheyenne’s average last frost is around May 20; Casper’s is around May 18. Both dates carry a 30% probability that frost could occur later—keep frost protection available through late May.

What is the easiest vegetable to grow in Wyoming? Kale is the most forgiving—it tolerates cold, heat, and drought, grows in any Wyoming zone, and can be harvested for months. Radishes are the fastest (22–35 days) and most fool-proof for beginners.

What USDA zone is Wyoming? Most of Wyoming is zones 3b–5a on the 2023 updated map, with the coldest mountain areas in zone 3b and the warmest southwestern pockets reaching zone 6a.

Can I garden in Jackson Hole with its 79-day growing season? Yes, but focus on cool-season crops—lettuce, spinach, kale, peas, radishes, carrots, and broccoli. Fast-maturing annual flowers like marigolds and cosmos work too. Warm-season crops are a gamble: the math requires a 55-day or shorter tomato variety planted immediately after last frost, with luck that frost holds off until September.

When should I plant garlic in Wyoming? Plant garlic in September or early October, 4–6 weeks before the ground freezes hard. Garlic roots establish before winter and produce summer bulbs. It’s one of Wyoming’s most reliable crops precisely because it works with the climate rather than against it.

Sources

• Growing Vegetables in Wyoming (B-1115R) — University of Wyoming Extension / Wyoming Extension
• Gardening Resources — Barnyards & Backyards, University of Wyoming Extension
• Seasonal Calendar — Barnyards & Backyards, University of Wyoming Extension
• Tips for Growing a Successful Vegetable Garden in Wyoming — Wyoming Livestock Roundup (citing Karen Panter, UW Extension Specialist)
• First & Last Frost Dates of Wyoming Cities — plantingzonesbyzipcode.com (NOAA Climate Normals 2020)