As you flip through seed catalogs or look at the growing requirements on the back of a seed packet, you will see a number (typically in parenthesis). This number, called ‘days to harvest’ or ‘days to maturity’ tells gardeners how many days it takes for a germinated seed or transplanted start (small plant) to produce the edible portion of the plant. For example, if a gardener selects a variety of fava bean that takes 110 days to maturity, then the gardener should expect 110 days between planting seeds and harvesting fava beans. A different variety may have longer or shorter days to maturity requirement.
Days to maturity is important to consider when selecting seeds because it is necessary that your growing season contain enough days for your garden plants to mature. Therefore gardeners must also know the average number of days in the growing season for their area. Length of growing seasons can be impacted by multiple factors like geographic location and elevation. For example, the average last spring freeze for Park City, Utah is June 13th, while only 30 miles away, the average last spring freeze in Salt Lake City, Utah is April 13th (two months earlier)! Growing season is defined as the period of time between the average first frost and the average last frost of the same year. See the chart below for a listing of Northern Utah cities and average growing season lengths. Average is just that, sometimes frosts come late in the spring or early in the fall. Growing season lengths can even vary between two locations in the same city!
|Northern Utah City||Average Last Spring Frost||Average Fall Frost||Average Growing Season|
|Brigham City||May 4||October 11||160 days|
|Layton||May 14||October 26||165 days|
|Logan (USU)||May 7||October 11||159 days|
|Ogden (AP)||April 29||October 20||175 days|
|Park City||June 13||September 6||85 days|
|Provo (AP)||April 28||October 11||167 days|
|Salt Lake City||April 13||October 31||2013 days|
|Tooele||May 7||October 15||162 days|
*For a listing of freeze information for 550 locations throughout Utah, visit climate.usu.edu, hover on the ‘resources’ tab, and select ‘freeze dates’.
Days to maturity does not tell gardeners when best to plant garden seeds or starts. For this information gardeners need to reference the seed catalog or seed packet. Stay tuned for upcoming blog posts on when to plant different types of garden plants outdoors, until then, let it snow!
Suggested planting dates for starting seeds indoors in Utah can be found on page 8 of Utah State University’s Home Vegetable Garden Fact Sheet . You can also visit our Gardener’s Almanac for other seed starting tips.