Zone 5b Planting Guide 2026 | Denver, Salt Lake City, Omaha Garden Calendar

Zone 5b gives you a slightly longer season than 5a — but Western 5b gardeners face altitude, dry air, and dramatic temperature swings that change the rules. Here are your 2026 dates, frost windows, and the varieties that thrive across this diverse zone.

USDA Hardiness Zone 5b at a glance

Minimum temperature

-15°F to -10°F (-26.1°C to -23.3°C)

Average last frost

April 18 (range April 10 – 25)

Average first fall frost

October 5 – 20

Growing season

135 – 160 days

Best planting window

April 25 – May 10 for warm-season crops

Where it falls

Denver, Salt Lake City, Omaha, Kansas City, Lincoln

Major cities in Zone 5b

Primary cities: Denver, CO • Salt Lake City, UT • Omaha, NE • Kansas City, MO • Lincoln, NE • Colorado Springs, CO

Also includes: Parts of Colorado, Utah, Nebraska, Kansas, Missouri, southern Michigan, and northern Indiana.

Try our Free Vegetable Planting Calendar by ZIP Code

Enter your ZIP code for a free, personalized planting calendar. See when to start seeds, transplant, and harvest 45+ vegetables, herbs, and flowers based on your USDA hardiness zone and frost dates.

Open Planting Calendar

2026 Zone 5b Planting Calendar

March — indoor seed starting

Crop	Start Date	Transplant Date	Notes
Tomatoes	March 5-20	May 1-10	Indeterminate varieties do well here
Peppers	March 1-15	May 10-25	Start early — peppers need heat
Eggplant	March 10-25	May 15-25	Warm soil is critical
Herbs (Basil)	March 20 - April 5	May 10-25	Very frost sensitive

April — cool-season crops

Crop	Direct Sow Date	Harvest	Notes
Peas	April 1-10	June-July	Tolerate light frost
Lettuce	April 5-20	May-June	Succession plant every 2 weeks
Spinach	April 1-15	May-June	Bolt-resistant varieties recommended
Radishes	April 5-20	May-June	Quick 25-30 day harvest
Carrots	April 10 - May 5	July-August	Succession plant monthly

May — warm-season planting

Crop	Plant Date	Harvest Start	Notes
Beans (Bush)	May 5-25	July-August	Direct sow after soil warms to 60°F
Corn	May 10-25	August-September	Standard-season varieties work
Squash (Summer)	May 10-25	July-September	Plenty of season for full production
Cucumbers	May 10-25	July-September	Succession plant for extended harvest

Best Varieties for Zone 5b

Tomatoes — reliable performers

Celebrity (70 days): Disease-resistant determinate, great yields
Early Girl (50 days): Fast to fruit, reliable
Mountain Merit (75 days): Late-blight resistant
Juliet (60 days): Prolific grape-type
Cherry tomatoes: Sun Gold, Sungold, Sweet Million

Peppers — proven winners

Sweet: California Wonder, King of the North, Carmen
Mild Hot: Anaheim, Poblano, Hungarian Wax
Medium Hot: Jalapeño, Serrano
Note: Superhots are possible but need a long indoor start

Cool-season stars

Lettuce: Buttercrunch, Red Sails, Salanova mix
Spinach: Bloomsdale, Space, Tyee
Peas: Sugar Snap, Oregon Sugar Pod, Little Marvel
Carrots: Bolero, Napoli, Yaya

Zone 5b Frost Information

Critical frost dates for 2026

Last spring frost

April 18 average (range April 10 – 25)

Safe planting date

May 1 – 10 (add 1 week for safety)

First fall frost

October 12 average (range October 5 – 20)

Latest recorded spring frost

May 8 (Denver area)

2026 climate considerations

Altitude factor: Denver-area gardeners at 5,000+ ft face stronger UV and faster soil drying
Variable spring: Front Range can swing 40°F in a day — harden off gradually
Hail risk: Common in Colorado May-June — use row covers or hoop tunnels
Low humidity: Western zone 5b is much drier than eastern — mulch aggressively

Frost protection strategies

Row covers: Floating row cover adds 4-6°F protection
Wall of water: Standard technique in Denver for early tomatoes
Raised beds: Warm faster in spring than in-ground beds
Mulching: Straw mulch conserves moisture and moderates soil temps

Zone 5b Success Tips

Soil and site preparation

Soil test: Western zone 5b often has alkaline soil — may need sulfur
Drainage: Rocky soils in mountain areas drain fast — add compost for water retention
Amendments: Most zone 5b soils benefit from 3-4 inches of compost worked in each spring
Wind protection: Especially important along the Front Range and Great Plains

Season extension techniques

Start seeds indoors: 6-8 weeks before last frost for warm-season crops
Use transplants: More reliable than direct seeding for tomatoes, peppers, eggplant
Succession planting: Stagger cool-season crops every 2-3 weeks
Fall gardens: Plant second lettuce/spinach crop in mid-August

Common Zone 5b mistakes

Planting too early: A warm March doesn't mean frost-free — wait for consistent warm nights
Underwatering: Western zone 5b is dry — drip irrigation is worth the investment
Ignoring altitude effects: Higher elevations mean cooler nights and stronger sun
Skipping wind protection: Great Plains and Front Range wind desiccates young plants

Monthly Zone 5b Garden Tasks

March

Start warm-season seeds indoors under lights
Order seeds and plants
Prepare garden beds when soil is workable (often late March)
Prune fruit trees before bud break

April

Direct sow cool-season crops outdoors (peas, lettuce, spinach, radishes)
Continue indoor seed starting for late crops
Harden off early transplants
Apply compost and turn beds

May

Transplant warm-season crops after last frost and soil warmth
Direct sow beans, corn, squash, cucumbers
Mulch around plants to conserve moisture
Install stakes, cages, and trellises

Get your exact dates

Frost dates shift sharply with elevation across Zone 5b. Use the free Planting Calendar for personalized variety recommendations and frost alerts for your ZIP code.

Last updated: March 6, 2026 | Zone 5b data based on USDA Plant Hardiness Zone Map 2023 and NOAA climate normals.