Heat stress
Heat stress in plants occurs when temperatures exceed the optimal range for growth, causing wilting, leaf scorch, and stunted growth. This happens because high temperatures increase transpiration rates, leading to water loss and reduced photosynthesis.
What you see
Heat stress is a condition that affects plants when they are exposed to excessively high temperatures, often combined with inadequate water supply. This stress can lead to a range of symptoms, primarily due to the plant's inability to maintain its water balance and perform photosynthesis efficiently. Unlike diseases caused by pathogens, heat stress is purely environmental and does not involve any infectious agents. When temperatures rise beyond a plant's tolerance level, the rate of transpiration increases, causing the plant to lose water faster than it can be absorbed through the roots. This results in wilting and, if prolonged, can cause permanent damage to the plant tissues. Leaves may develop scorched or crispy edges as a direct result of dehydration and heat exposure. It is important to distinguish heat stress from other issues such as nutrient deficiencies or pest infestations. Heat stress typically occurs during periods of high temperatures and is often accompanied by dry soil conditions. Unlike diseases, there are no visible pathogens or insect damage associated with heat stress.
Symptoms
- Wilting
- Scorched or crispy leaf edges
- Leaf drop
- Stunted growth
Why it happens
Excessively high temperatures causing increased transpiration and water loss.
Conditions that favour it
- Prolonged high temperatures
- Inadequate watering
- Poor soil moisture retention
- Lack of shade
- High sun exposure
Plants most affected
- Tomato
- Pepper
- Lettuce
- Cucumber
- Bean
- Squash
- Rose
- Azalea
- Rhododendron
- Hydrangea
How to correct it
Educational information only, and not a substitute for professional diagnosis. Identify the problem before treating it, and check that any product is registered for this plant and this use where you live.
Cultural control
- Provide shade during peak sunlight hours
- Increase watering frequency
- Mulch to retain soil moisture
- Improve soil drainage
- Ensure adequate air circulation
Organic options
- Compost
- Seaweed extract
- Fish emulsion
Prevention
- Monitor weather forecasts to anticipate heat waves
- Water plants early in the morning
- Use shade cloths during hot periods
- Maintain proper soil moisture levels
- Select heat-tolerant plant varieties
Sources
- University of California Agriculture and Natural Resources
- Clemson Cooperative Extension
- Texas A&M AgriLife Extension