• slide
  • slide
  • slide
  • slide
  • slide
  • slide
  • slide
  • slide

Garden Planning: Frost Dates and Frost-Free Growing Days

Grab the calendar, your garden plans and take a look at your area’s climate history before you start planting. 

We talk a lot about cold hardiness when planning our gardens and selecting plants.  But we also need to look at the number of frost-free days in our area.

This number influences our plant selection and planting time indoors and out.  Planting dates, indoors and out, are often based on the average last spring frost.

Next, count the number of days between the average last spring and first fall frost.  This is the average number of frost-free days in your location.  Compare this to the plant tag, seed packet or catalogue descriptions.  Most provide a  “number of days to harvest or bloom”. You may need to grow shorter season cultivars, start the seeds indoors, or use season extending techniques to grow plants that require a longer growing season than yours.

A bit more information:  Heat is also a limiting factor when gardening.  Many plants suffer damage when temperatures rise over 86 degrees Fahrenheit (30 degrees Celsius).  The American Horticultural Society Plant Heat-Zone Map has divided the United States into zones based on the average number of 86 degree and warmer days.  Visit AHS-heat-zone-map.pdf for more information.

Upcoming Live Events
& Webinars


Jan. 10, 2026
Greater Des Moines
Botanical Garden

Des Moines, IA
Register here

Jan. 28, 2026
FREE WEBINAR: 
Past, Present & Future of Mitchell Park and its Conservatory, the Domes  
Register here

Feb. 13 - 15, 2026
PBS Wisconsin
Garden & Green Living EXPO

Madison, WI
More information

Feb. 18, 2026
FREE WEBINAR: 
Plants that Go the Distance
Register here

March 26, 2026
FREE WEBINAR: 
Getting Started Growing Vegetable and Flower Gardens
Register here

WATCH ON-DEMAND WEBINARS

Learn More

Book an Appearance

Learn More

Enter for the chance to win a Milwaukee Domes Alliance membership & merchandise!

ENTER NOW