Ask an Expert: When to Plant? That is the Question

Taun Beddes

05/01/2017

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Frost on PlantsOne day it is sunny and warm, and the next day it is raining and cold. Or in northern Utah, it could even be snowing.

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 their plants to frost.

As you determine when you should plant, consider the geographic characteristics of where you live. 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 increases temperatures and delays 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.

 

Average Frost Dates for Various Utah Locations
(Note that these dates are averages and can vary from year to year.)

 

 

            Frost Dates

 

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

 

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