It's two o'clock on a July afternoon. You walk out to check the garden, and your squash leaves are drooping so low they're nearly touching the mulch. Your tomato plants look like they've given up on the whole season. If your first thought, every single time, is “I need to water right now,” hold on a second before you grab that hose. Because that dramatic afternoon collapse you're looking at likely has absolutely nothing to do with how much water is in your soil.
So today on Just Grow Something we're covering three things: what's actually happening inside a plant's cells when the temperature spikes, the specific ways to tell heat stress wilting apart from drought stress wilting, and what heat stress does beyond the leaves, because your tomatoes and peppers and squash can look perfectly fine and still be failing to set fruit, and that's a heat problem too.
Let's dig in.
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References and Resources:
Graci, S., & Barone, A. (2024). Tomato plant response to heat stress: a focus on candidate genes for yield-related traits. Frontiers in Plant Science, 14, 1245661. https://doi.org/10.3389/fpls.2023.1245661
Sellami, D., & Kooli, S. (2025). Physiological and growth responses of tomato plants to heat stress. Discover Plants. https://doi.org/10.1007/s44372-025-00462-3
University of Maryland Extension — Drought and Excessive Heat Stress https://extension.umd.edu/resource/drought-and-excessive-heat-stress
University of Maryland Extension — Pollination of Vegetable Crops in a Changing Climate https://extension.umd.edu/resource/pollination-vegetable-crops-changing-climate
NC State Cooperative Extension, Beaufort County — What "Wilting" Really Means: Heat Stress vs. Water Needs https://beaufort.ces.ncsu.edu/news/what-wilting-really-means-heat-stress-vs-water-needs/
Oregon State University Extension — Heat Wave in the Garden: How to Identify and Prevent Heat Stress in Plants https://extension.oregonstate.edu/catalog/em-9556-heat-wave-garden-how-identify-prevent-heat-stress-plants
Oregon State University Extension — Why Vegetables Drop Blossoms https://extension.oregonstate.edu/news/why-vegetables-drop-blossoms
Oregon State University Extension — Mother Nature May Need Help to Pollinate Squash and Cucumbers https://extension.oregonstate.edu/news/mother-nature-may-need-help-pollinate-squash-cucumbers
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