Determining when to plant a garden can be especially confusing and Utah's unpredictable varied climate, or last frost days can vary by many days within just a few miles. Many experienced gardeners have planted and later lost their plants to frost.
Geographic characteristics of where you live can help in determining where to plant. Where 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 heat from buildings and roads.
In addition to frost information, it's important to take into account the needs of the plants. Vegetables planted locally fall into four basic categories hearty, semi hearty, tender and very tender Depending on which category a plant belongs to planting dates vary from early spring to early summer.
Consider the following: hearty 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 60 and 45 days before the average last frost, the 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.