Spring Has Spring But...Frost Still LIkely

Taun Beddes

03/23/2015

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With the unusually warm weather this year, many gardeners are getting anxious to get outside and work in the yard. Determining when to plant a garden can be especially confusing in Utah’s unpredictable, varied climate where last-frost dates can vary by many days within just a few miles. Many experienced gardeners have planted and later lost the plants to frost.

An example of how fickle Utah’s climate can be is in Cache Valley. Frost-free days vary from an average of 113 days in Lewiston and Trenton to 158 days on the USU campus. Similar examples are common around the state.Frost on plants in springtime

Geographic characteristics of where you live can help in determining when to plant. When a yard is located in a populated area or on a mountain bench, it usually has a longer growing season. Other areas located at slightly lower elevations where cold air drains and cannot escape have a shorter season. This is why local commercial orchards are generally located on benches. Additionally, urban and suburban areas are slightly warmer than surrounding areas due to the urban heat effect. Heat from buildings and warmth generated by sunlight reflected from roads and other surfaces increase temperatures and delay frost. It can be helpful to chat with a local farmer or experienced gardener in your area to determine what works for him or her regarding when to plant.

In addition to frost information, it is important to take into account the needs of the plants. Vegetables planted locally fall into four basic categories: hardy, semi-hardy, tender and very tender. Depending on which category a plant belongs to, planting dates vary from early spring until early summer. Consider the following:

  • Hardy vegetables, including asparagus, broccoli, cabbage, onions, peas and spinach, can be planted as soon as the soil is workable in early spring. This usually ranges between 45 and 60 days before the average last frost. These same vegetables can be safely planted until the average last frost date.
  • Semi-hardy plants, such as beets, carrots, lettuce and potatoes, can be planted one to two weeks after the hardy group. These can be planted until the average last-frost date.
  • Tender vegetables, such as celery, cucumbers, corn and most beans, should be planted on the average last-frost date. 
  • Very tender plants, such as squash, beans, melons, tomatoes, eggplants and peppers, should not be planted until at least a week after the average last frost. Even if frost does not occur before this time, these plants will not grow well and are more susceptible to disease until warmer weather. 

If you have lost plants to frost, you are not alone, and all you can do is try again. For more information on fruit and vegetable gardening, visit the USU Extension website at: https://extension.usu.edu/yardandgarden/.

Average Frost Dates for Various Utah Locations

 

 

 

City

Last

First

Frost-Free Days

Alpine

May 20

September 30

136

Blanding

May 13

October 12

153

Cedar City

May 10

October 5

148

Delta

May 17

September 28

134

Farmington

May 5

October 10

158

Fillmore

May 16

October 4

140

Huntsville

June 11

September 9

  89

Kanab

May 7

October 20

166

Lake Town

June 15

September 10

  87

Logan

May 14

September 25

135

Morgan

June 6

September 11

 98

Moroni

June 1

September 18

109

Ogden

May 1

October 24

176

Park City

June 9

September 1

  92

Price

May 12

October 7

148

Roosevelt

May 18

September 25

130

Spanish Fork

May 1

October 13

165

St. George

April 6

October 28

205

Tooele

May 7

October 14

159

Tremonton

May 3

October 10

160

Vernal

May 27

September 22

118

By: Taun Beddes, Utah State University Extension horticulturist, 801-851-8460, taun.beddes@usu.edu