Sunday, May 10, 2009

Tomato variety choices

There are hundreds of tomato varieties and your garden center probably stocks ten to twenty. Which one is right for you?

In recent years, heirloom tomatoes have been in vogue. Unfortunately some of these varieties require a relatively large number of days to harvest. Examples are Purple Cherokee (85), Yellow Brandywine (90) ["potato leafed" variety photo below left] and Beefstake (85 days).

In Denver the average growing season is 155 days (May 10 to Oct 11). In some years like 2007 the growing season is short, only 123 days (June 8 to October 8). In addition, there were only 81 days with night temperatures greater than 55 degrees F. Why is this last tidbit important?

Tomatoes require warm night temperatures for growth. Night temperatures below 55 degrees F tend to slow and shut down growth. Depending how cold the nights, growth may take days to resume. This loses you valuable time in the race to tally growing days for maturity.

The high and dry environment of Colorado’s Front Range creates a summer climate that has warm days (80 or 90 degrees F) and thirty degree cooler nights due to radiational cooling (50 or 60 degrees F). Summers are very comfortable for people but not as conducive to growing heat-loving crops like tomatoes that prefer the warm nights of the Midwest and Eastern U.S. where the humidity prevents heat loss at night.

The other factor that decreases yield of tomato fruit is the arrangement of the flower. Varieties that do well here tend to have reproductive parts tucked well into the staminate cone in the middle of the flower. When reproductive parts protrude to or beyond the cone opening, they dry in our low humidity and wither before they pollinate. Tomatoes bred in New Jersey, Florida and other places in the East often don’t yield well here for this reason.

Modern tomato varieties tend to require a smaller number of days to harvest. Many cherry types are 50 to 60. ‘Early Girl’ and derivations are in the low 60’s. ‘Celebrity’ is 70. The ‘Boy’ types are in the low 70’s. My advice is to choose a variety requiring 80 or fewer days to harvest.

Next post, microclimate location and tomato success.

Tomato photos credit: Carl Wilson


  1. I've had great success with Early Girl in past years -- a lovely round tomato. Also, all kinds of grape and cherry tomatoes have grown well for me.

    I do miss the giant slicing tomatoes you can grow in the midwest!

    Thanks for a great blog.
    -Beth, Lafayette, CO

  2. I'm trying several new varieties this year, including Early Girl. Thanks for the tip abut the flowers -- I'd not heard this before!

    Are there any resources that list/compare flower types for particular tomato varieties? I'm also attempting to grow San Marzano, Red Siberia, Patio Prize, and Juliet, and hadn't considered how our lack of humidity might affect their blooms.

    Thanks again,

    Laura in Ft. Collins

  3. I've had the best luck with Early girls although this cool, damp spring is proving to be a challenge.