Colorado planting calendar

When to put transplants or seed in the ground across Colorado, worked out from the average last spring and first fall frost for each USDA zone in the state, and what to line up before you commit ground. Written for farms that sell what they grow.

Your zone in Colorado: frost dates

Zones 4b–6b run through Colorado. Frost dates are long-term averages for planning, not a forecast for your field.

  • Zone 4b
    Steamboat Springs and the mountain valleys
    Last frost
    ~May 15
    First frost
    ~September 22
    Frost-free days
    130
    Winter low
    -25°F to -20°F
  • Zone 5a
    Fort Collins and the northern Front Range
    Last frost
    ~May 8
    First frost
    ~September 29
    Frost-free days
    144
    Winter low
    -20°F to -15°F
  • Zone 5b
    Denver, Boulder and Colorado Springs
    Last frost
    ~May 1
    First frost
    ~October 6
    Frost-free days
    158
    Winter low
    -15°F to -10°F
  • Zone 6a
    Pueblo and the lower Arkansas valley
    Last frost
    ~May 1
    First frost
    ~October 1
    Frost-free days
    153
    Winter low
    -10°F to -5°F
  • Zone 6b
    Grand Junction and the western slope
    Last frost
    ~April 24
    First frost
    ~October 8
    Frost-free days
    167
    Winter low
    -5°F to 0°F

What it costs to grow an acre in Colorado

No published Colorado budget is transcribed here yet, so this page shows planting dates only — we do not publish cost figures we cannot source. Neighboring state budgets from NC State, UGA and UF/IFAS are on the crop profitability page.

Every figure is transcribed from a published land-grant enterprise budget for that state. These are planning budgets built from grower panels and dealer quotes, not surveys of what farms actually spent — your invoices override them everywhere they exist.

When to plant Colorado's main crops

Calculated for Zone 5b (Denver, Boulder and the Front Range). Pick your own zone on the crop page.

What zone is my farm?

  • Steamboat SpringsZone 4b
  • Fort CollinsZone 5a
  • DenverZone 5b
  • PuebloZone 6a
  • Grand JunctionZone 6b

If your farm sits in a zone that is not listed here, start from the calendar index and pick the closest match, then confirm with your county extension office.

Before you commit ground

A planting date tells you when a crop can grow — not whether it pays. Work out your breakeven price, then line up who is buying before you plant.

Colorado planting and cost questions

What USDA planting zone is Steamboat Springs, Colorado?
The calendar carries Steamboat Springs in Zone 4b. Average last spring frost is around May 15 and average first fall frost around September 22, which is about 130 frost-free days.
What USDA planting zone is Fort Collins, Colorado?
The calendar carries Fort Collins in Zone 5a. Average last spring frost is around May 8 and average first fall frost around September 29, which is about 144 frost-free days.
When should I plant tomatoes in Colorado?
In Zone 5b (Denver, Boulder and the Front Range), May 8 – May 29 july 29 – august 26

Other state pages

Dates are calculated from average first and last frost dates for each zone. Your microclimate, elevation and soil temperature can shift any window by a week or more — treat these as starting points and keep your own records.