Posted: July 03, 2024

Summer in Massachusetts brings not only warm days and vibrant greenery but also the potential challenges of heat waves.

These periods of prolonged heat can significantly impact the health and vitality of landscapes, whether in urban settings, suburban neighborhoods, or rural areas. And while heat and drought are related, there is a difference between heat stress and drought stress. Heat stress occurs when temperatures are excessively high, typically above what the plant can tolerate, while drought stress results from inadequate water availability in the soil relative to the plant's needs. These two phenomena occur concurrently during periods of hot, dry weather.

Understanding how to care for Massachusetts landscapes during heat waves is crucial for preserving the beauty and functionality of outdoor spaces.

Let’s look at the common signs of heat stress in plants, watering tips during extreme heat, and how to protect plants from heat stress during heat waves.

What Are the Visible Signs & Symptoms of Heat Stress in Plants

Heat stress in plants manifests through a variety of visible signs and symptoms, which can vary depending on the severity and duration of the heat exposure. Recognizing these signs early can help you take prompt action to mitigate damage and support plant recovery. Here are the common visible signs and symptoms of heat stress in plants:

  • Leaf curling: Leaves curl or roll inward or upward, reducing the leaf surface exposed to direct sunlight and minimizing water loss through transpiration.
  • Leaf wilting: Leaves become limp, droop, or appear flaccid. Wilted leaves indicate the plant is losing more water through transpiration than it can absorb from the soil, often due to high temperatures and insufficient moisture.
  • Leaf scorch: Leaf margins or entire leaves turn brown, yellow, or appear burned. Scorching occurs when high temperatures and intense sunlight cause rapid water loss from leaves, leading to cellular damage and death of leaf tissue.
  • Leaf yellowing or chlorosis: Leaves turn yellow, particularly between veins. Chlorosis can result from heat stress reducing the plant's ability to take up nutrients from the soil, especially iron and manganese.
  • Leaf dropping: Leaves drop prematurely from the plant. Heat stress disrupts the plant's hormonal balance, leading to accelerated aging and shedding of leaves as a survival mechanism.
  • Stunted growth: Plants show reduced overall growth, with smaller leaves and shorter stems. High temperatures inhibit metabolic processes necessary for growth, such as photosynthesis and nutrient uptake.
  • Flower or fruit drop: Flowers or developing fruits drop off prematurely. Heat stress can interfere with pollination, reduce flower viability, or cause flower and fruit tissues to dry out and abort.
  • Bark cracking: Bark on branches or trunks develops cracks or fissures. Rapid temperature fluctuations, particularly during heat waves, can cause the outer bark layers to dry and crack.
  • Increased susceptibility to pests and diseases: Plants weakened by heat stress are more susceptible to pest infestations and fungal or bacterial diseases. Stressed plants have compromised defenses and weakened ability to respond to insect pests and pathogens.

How To Protect Plants During Heat Waves & High Temperatures

Protecting plants during heat waves and high temperatures is crucial to ensure their health and survival.

Try these strategies when it comes to helping your plants endure heat and drought periods:

  • Watering: When watering during a heat wave, water deeply each week to encourage root growth and prevent excess salt buildup in the soil. Watering early in the morning minimizes water loss through evaporation. Drip irrigation can deliver this water right to the plant roots where it’s needed most. How much water should I give my plants during a heat wave? Younger or newly planted or transplanted trees will require more water than established trees, amounting to 5 to 15 gallons of water weekly.
  • Mulch: Use a 2- to 4-inch layer of organic, shredded, hardwood mulch to insulate the soil, retain moisture, regulate soil temperature, and reduce stress on plant roots.
  • Monitor and protect plants: Look for the signs of heat stress in plants listed above to ensure early detection and prompt intervention.
  • Provide good air circulation: Make sure your plants are appropriately spaced for decent air circulation.

Things To Do & Avoid During Unexpected Heat Wave

In addition to the things to do when it comes to how to protect plants from heat stress during heat waves, there are also some things you should avoid, including:

  • Choose the appropriate fertilizer: Using quick-release nitrogen can cause salt burn in extreme heat; slow-release nitrogen is a better choice.
  • Adjust pruning practices: While pruning out dead branches can improve air circulation and reduce competition for nutrients, you never want to prune heavily in heat because it stimulates new growth. This can stress the plant and lead to it needing more water, which is challenging during drought.

Power Heat Stress Plant Care

Once drought or heat stress in plants has passed, you want to continue to monitor your trees and shrubs to ensure recovery.

First, let’s start with watering tips during extreme heat. Continue that slow, deep, and infrequent watering. Never overwater to avoid root rot. And continue that early morning watering.

For smaller plants that may be impacted, setting up some temporary shade can aid their recovery.

And don’t neglect the mulch; just don’t let that mulch pile up around tree trunks to avoid rot or disease issues.

How do you know your plants are recovering from heat and drought stress? Look for improved appearance and the resolution of symptoms, as well as signs of new growth like fresh leaves, shoots, or flowers. But be patient and continue to monitor the plant’s progress since recovery can take some time. Providing consistent care and monitoring for any ongoing issues will support plant recovery and help trees and shrubs regain their strength for future challenges.

At Hartney Greymont, we have both ISA and Massachusetts certified arborists located in Needham, Concord, Danvers, Cape Cod, and the surrounding areas to help with heat stress in plants.

Worried About Climate Change And Your Plants? Check Out How You Can Adapt Your Landscape Care Amid Climate Change In Massachusetts.

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