Peonies at Fox Hollow Farm, Nenana, AK.
This tool was created with input and expertise from Alaska farmers and gardeners, including experts from the UAF Georgeson Botanical Gardens, Spinach Creek Farm, Calypso Farm, and the Alaska Peony Growers Association. Funding was provided by the U.S. Department of Agriculture via the Alaska Climate Adaptation Science Center.
Length of Growing Season
Time between the last cold day in spring (based on the temperature threshold you select: 32°F, 40°F, or 50°F) and the first cold day in fall. Here, you can see projections of start/end dates and the number of days in between. This can help you decide if a crop is worth planting in your area. ”Days to maturity” information is often provided on seed packets. But keep in mind that cool temperatures can slow growth, so also check our “Growing Degree Days” tool.
Annual Minimum Temperature (AMT)
Perennials such as fruit trees and shrubs have to be hardy to survive Alaska winters. Many can’t withstand temperatures below certain thresholds. “Cold hardiness” is just one gauge of whether a crop is suitable to a particular region. Many other factors affect winter survival, such as the insulating value of snow, the moisture content of the ground, the presence or absence of permafrost, and the number of freeze-thaw cycles that occur. Future versions of this tool may include some of these factors.
Growing Degree Days (GDD)
Used to estimate how much heat is available to crops. Heat units are added up daily, throughout the growing season, to create a cumulative total. Plants tend to reach particular growth stages when cumulative GDD reaches the necessary values.
The USDA uses Plant Hardiness Zones as the standard by which growers can determine which plants are likely to thrive at a given location. Many seed manufacturers reference these zones. Hardiness maps are based on the average annual minimum winter temperature. These zones are only a rough guide. Because they are based on winter temperatures, they are of greatest importance for perennials such as fruit trees or peonies. It may make more sense to choose summer crops (annuals) based on our Growing Degree Day or Growing Season tools. Also, variations based on very fine scale differences in slope or elevation are too small to show up on these maps.