Temperatures are rising, and plants are taking a beating, especially tomatoes. From blossom loss to poor growth, this South American fruit can’t always beat the heat. “Tomatoes grow best at uniformly moderate temperatures between 65 to 85 degrees Fahrenheit,” claims Colorado State University, “This is why a high altitude, semiarid climate like Colorado with wide daily temperature swings is not a favorable area for tomato growing (PlantTalk, 2025).” It’s important to identify heat stress compared to fungal issues. We’re going to go over some techniques for identifying heat stress and keeping tomatoes cool!

Heat Stress Signs

Are your blossoms falling off the tomato plant? Or has their growth suddenly halted? What about wilting? These are all signs of heat stress in tomatoes. Blossom loss is caused by high temperatures interfering with pollination. Dry winds don’t carry pollen well, so blossoms go unfertilized and die off. Halted growth is caused by cool night temperatures and scorching hot day temperatures, the contrast induces stress. And wilt is caused by numerous factors, not just heat. If the soil is dry, then it may be caused by accelerated evaporation due to heat. Fungal wilt disease is another issue caused by heat, due to the combination of a moist environment and then sudden heat. There are several varieties of fungal wilt, so we recommend checking out this article to fight them accordingly: Click here!

Fighting Heat

Time to beat the heat! Anything that retains moisture and shields plants from the sun will protect your tomatoes. We recommend a shade hail cloth, preferably one with a percentage like 30% light blockage. This filtered shade cloth will allow the tomatoes to get enough light while also creating a cool environment. Shade cloth shouldn’t be draped on the plant, it should be supported by PVC pipe or a tomato cage. Plus, it will also protect against hail when it hits!

Applying mulch will help retain moisture. Apply mulch in vegetable beds and containers. Make sure not to layer mulch right against the stem of the plant. Leaving space between mulch and plants helps prevent further fungal infections. Make sure the mulch isn’t dyed either. Dye isn’t safe for human consumption. Leaf mulch will also do the same thing! Leaf mulching involves shredding leaves that fall from trees to make your own mulch! It retains moisture like shredded wood mulch but also gives back precious nitrates, helping your tomatoes grow! To make leaf mulch you can buy a leaf mulcher or smash them with a weed whacker or mower. It’s obviously July, so leaves aren’t expected to fall until autumn but garden centers often have leaf mulch piles people drop off for others to take. We certainly do! Give us a call before driving home to make sure we have bagged. 

Regardless if you choose to add mulch you may have to water more as the heat increases. We recommend following Colorado Springs Utilities for watering times. But when watering, water deep. Use a bubbler sprinkler or slow-release irrigation system and water in intervals. This is so the water penetrates the soil and soaks deeper, ensuring lower evaporation rates. This also helps strengthen roots and drought immunity in the plant!

Fighting heat isn’t easy, Colorado is a semi-arid high desert after all. Not all tomatoes will survive super hot summers, but these cool techniques will help preserve them! Plus, these techniques can be used on other plants too, from vegetables to annuals! 

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“Colorado State University.” PlantTalk Colorado. Accessed June 26, 2025. https://planttalk.colostate.edu/topics/vegetables/1835-tomato-questions-abound-heat/. 

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