Northern Utah Vegetable Planting Guide
The coldest winter temperatures in northern Utah can range from zero degrees Fahrenheit to minus 25. To grow vegetables successfully in this extreme climate, you need to find out when the danger of frost in your location has passed. The Cooperative Extension, a division of Utah State University, has collected this information for all areas of the state.
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Northern Utah Counties and Hardiness Zones
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The northern half of Utah includes Box Elder, Cache, Rich, Weber, Morgan, Davis, Summit, Daggett, Tooele, Salt Lake, Utah, Wasatch, Duchesne, Uintah, Juab and Carbon counties.
The U.S. Department of Agriculture's hardiness zones for the northern half of the state range from zone 6b, which has an average low winter temperature of zero to minus 5 degrees, to zone 4b, with an average low winter temperature of minus 20 to minus 25 degrees.
The Wasatch Mountains
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The big weather maker in the state is the Wasatch Range, which runs north and south through 160 miles of the state. Air coming in from the West Coast drops its moisture as it climbs over the mountains, making the west side of the range the wettest, and most fertile, part of the state. The areas immediately adjacent to the Wasatch Mountains tend to have the coldest winter temperatures.
Frost Dates
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To determine when it's safe to plant your vegetables, you need to know the average first and last frost dates for your location. The Utah State University Cooperative Extension Service (USUCES) has documented this data for communities throughout the state.
In Logan, which is almost on the Idaho border, the average last and first frost dates are May 25 and Sept. 25. In Castle Dale, which lies a little east of the center of the state, the average last frost date is May 22 while the average first frost date is Sept. 23.
When to Plant Seeds Outside
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USUCES suggests you plant broccoli, cabbage, lettuce, onion, pea and spinach seeds four to six weeks before the last frost date. These are tough plants that won't suffer if they happen to experience frost.
Two to four weeks before the last frost date, you can plant beets, carrots, chard, onion sets and radishes. On the last average frost date, it's safe to plant beans, squash, corn and tomatoes. You should sow seeds for tender plants like peppers, eggplants, cucumbers and melons a week after the last frost date.
Starting Seeds Inside
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If you prefer to get a jump on the season by starting your seeds indoors, you should plant tomato and pepper seeds six to eight weeks before the last frost. Two to three weeks before that date, you can plant seeds for squash, cucumbers and melons.
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