Thursday, May 14, 2009

Tomatoes love night heat

Last post discussed heirloom and modern tomato varieties and adaptation. Warmer gardening situations, particularly at night, will help both be productive.

Grow tomatoes in full sun or choose a hot south or west exposure. If there is masonry nearby that can absorb heat by day and radiate it at night, it’s often for the better in our high elevation climate. Examples of these heat sinks are walls [left photo with lattice], pavement and rock.

Some gardeners have placed large rocks between tomato plants to act as “warming stones” [photo right] at night. The nice thing about this idea is that they can be removed if necessary during 90 to 100 degree F mid-summer heat when nights are warm and re-introduced in late summer as weather cools.

People who succeed with longer days to harvest varieties usually garden in the center of a city (heat island), locate their garden in a warm exposure and have heat-retaining pavement or walls near their tomatoes. A warmer than average microclimate at night is the reason behind their success at 5280’, mile-high Denver elevation.

Gardeners in Castle Rock (6200’ elevation) and Colorado Springs (6000 – 7200’) will have shorter growing seasons and more difficulty growing long season tomatoes. Carefully selected exposure, microclimate and use of season extenders such as Wall O’Water®, Season Starter™ and Kozy Coat™ [See May 3rd post] are even more important in these situations. Higher elevation foothill gardeners are more challenged. Mountain gardeners with very short growing seasons should consider growing warm season vegetables in greenhouses.

Have a favorite location or microclimate for your tomatoes? Discuss it by clicking comment below to let us know.

[Tomatoes on brick wall and warming rock photos – Carl Wilson]


  1. HI Carl, So this season so far has been a chilly challenge for tomatoes. I used to be a pro but this year has proven otherwise. Aside from the yellow leaves I'm attributing to too much moisture, the leaves have developed these brown varicosities or striations in them. Do you know what that is from, how detrimental to the plant is it, and can I correct it? Thanks! Sheila

  2. Problems are hard to diagnose from words. If possible, take plant sample to a garden center or CSU Extension office (locate using this URL Meanwhile, fertilize plants and get them growing vigorously. They may outgrow some early difficulties.