When I first came to wheat Ridge, I used to worry about the cold for my garden and focused on finding cold tolerant trees and plants. But now that I have been here for 15 years of gardening, I think the heat is actually more of a challenge, especially for the vegetables and fruits. Wheat Ridge’s highest recorded day temperature is 103F (for Denver it is 105F). There were 103F temps recorded in June of 1990 and 2012 and in July of 1989 and 1990. Those seem to be our peak max temp events thus far, however, it is fairly typical each year for us to have a few or several days over 100 degrees (2024 had 6 days, 2012 had 13)!

High temperatures also tend to feel hotter here compared to other areas (I’m thinking about south Texas) because of the combination of elevation and low humidity. Located at approximately 5,459 feet of elevation, we experience UV radiation at levels more than 20% higher than at sea level because there is less troposphere to screen out the UV. The same temperature feels more intense at this altitude. The low humidity here also makes it easier for water vapor to evaporate quickly and can lead to plants drying out faster (especially potted plants!)

Most of the vegetable seeds that can be purchased will come from other areas of the country that don’t have the same climate stresses, so growing them out may be a challenge here. Many vegetables and fruits have built in preferences for temperatures and UV lower than what they will experience here. If pushed beyond their limits, tomatoes will shut down and not bloom, even peppers will slow production if too hot.

Plants have many ways of coping with severely hot weather and high UV. They can moderate their growth rate and alter transpiration rates to a certain extent. Sun scorching and sunscald may leave damaged leaves and fruit. The traditional symbol of “I’m in trouble” in plant language is wilting. In hot weather, I am always watching for these signs of stress.

Over a season of exposure, some plants may develop shorter stems or thicker leaves to cope. Over successive generations of growing, the plants may find a way to adapt to these climate conditions. Saving seeds from plants grown here over successive generations can be very beneficial. If possible, buying seeds that come from local growers from this area or trading seeds with other gardeners would be a good idea because the plants have already experienced these climate conditions for a generation or two.

When the garden is confronting a 100 degree or higher day (which we know is going to happen a couple times each season), the sage advice is to make sure it is watered early in the day (but not overwatered). If you have plants that have been scorched or scalded by the sun, remove the damaged leaves, but try not to over prune. Avoid fertilizing that day and consider using some temporary shade cloths or umbrellas.

For my garden, the integration of fruit trees with the vegetable garden is specifically to provide rotating areas of shade for the plants during the day to cut down on the fierce effects of high UV. With multiple levels or stories of plants grown together for shade, and with a good supply of mulch to decrease evaporation, it is possible to moderate the harmful effects of baking too much in a really hot sun.