Selecting best vegetable varieties for our climate

Question: I need help in selecting vegetable seeds and plants to fit our climate. I had too many tomatoes that were not able to ripen. My winter squash and melon varieties were almost a complete disappointment. Could you suggest varieties that would ripen earlier?

Answer: Our frost-free growing season in Idaho Falls is only about 110 to 120 days. Cool night temperatures slow maturity of warm season vegetables like tomatoes, melons and squash by two weeks or longer.

Most seed packets, catalogs, and online seed sources rate vegetable varieties by “days-to-maturity.” Many vegetable plant tags also include a days-to-maturity rating. Days-to-maturity is the number of days from planting to first harvest under ideal growing conditions. Ratings for hardy or cold tolerant vegetables fit our climate fairly well. These include almost all of the root, leaf, and flower bud vegetables plus peas.

Frost tender or heat tolerant vegetables need to have about two weeks added to the days to maturity rating. Tender vegetables include almost all the fruiting vegetables such as tomatoes, peppers, corn, squash, cucumbers, melons and beans.

Tomato varieties are the most critical. An 80 day tomato will take about 94 days from transplanting to the first ripe fruit in Idaho Falls. If planted at the normal time in late May, the first fruit will be harvested about the end of August. That leaves only about three weeks of harvest time before average first frost. It is obvious that a 60 day tomato would bear fruit about three weeks earlier and double the length of harvest period.

There are several ways to speed up the maturing process. One way is to plant larger 4 inch or gallon size plants. Another is to use black or colored plastic mulch which warms the soil and speeds growth. Plastic tunnels, floating row covers and Wall-O-Water protectors all increase the air temperature around plants and speed growth. Earlier planting alone without these growing aids seldom improves earliness, because temperatures are too low for stimulating growth.

Another way to use days-to-maturity ratings is to plant two or more varieties with different maturity ratings to spread the harvest period. This works well for sweet corn, onions, tomatoes, and cabbage. An early 60 to 65 day cabbage will be mostly harvested by the time a later 80 day cabbage is ready. I like to plant three maturities of sweet corn, with ratings about 10 days apart, such as 60 to 65, 70 to 75 and 80 to 85 days. Since sweet corn is a little more frost tolerant than other tender vegetables, I plant corn in early to mid-May. Some of the mid-season tomatoes are larger and have better flavor than the earliest varieties, so I plant both. I avoid planting tomatoes with a rating of more than 80 days.

Allen Wilson can be contacted at