The Frank P Matthews Guide to Tree Watering and Care During Hot Weather

As temperatures rise during the summer months, ensuring that trees receive adequate water and care becomes paramount. Trees, especially newly planted ones, are susceptible to heat stress and drought, which can compromise their health and growth. This comprehensive guide provides in-depth insights and technical advice on effective tree watering and care practices to help your trees thrive during hot weather.

Understanding Tree Water Needs

Trees, like all plants, require water for essential physiological processes, including photosynthesis, nutrient transport, and transpiration. During hot weather, the rate of transpiration increases, leading to higher water loss. This necessitates an increased water supply to maintain tree health.

Factors Influencing Tree Water Requirements

1. Different tree species have varying water needs. For example, drought-tolerant species like oaks require less frequent watering than water-loving species like willows. Young and newly planted trees have smaller root systems and require more frequent watering than established trees with extensive root networks. Soil type is also important, sandy soils drain quickly and require more frequent watering, while clay soils retain moisture longer but may need careful monitoring to prevent waterlogging. Finally, high temperatures, low humidity, and strong winds increase water loss through transpiration, necessitating more frequent watering.

Best Practices for Watering During Hot Weather

1. Deep Watering:
   • Deep watering ensures that water reaches the tree’s root zone, promoting deep root growth and increasing drought resilience. Apply water slowly and deeply, allowing it to penetrate 12-18 inches into the soil.
   • Use a soaker hose or drip irrigation system to deliver water directly to the root zone while minimising evaporation.
2. Watering Schedule:
   • Water trees early in the morning or late in the evening when temperatures are cooler and evaporation rates are lower.
   • For young trees, water every 2-3 days during hot weather. Established trees may require watering every 7-10 days, depending on soil moisture levels.
3. Mulching:
   • Apply a 2-4 inch layer of organic mulch (e.g., wood chips, bark) around the base of the tree, extending to the drip line. Mulch helps retain soil moisture, regulate soil temperature, and reduce competition from weeds.
   • Avoid piling mulch against the trunk, as this can lead to rot and pest issues.
4. Soil Moisture Monitoring:
   • Regularly check soil moisture levels using a soil moisture meter or by inserting a screwdriver or garden trowel into the soil. Water when the top 2-3 inches of soil feel dry.
   • Ensure that the soil is moist but not waterlogged. Overwatering can lead to root rot and other issues.
5. Avoid Watering the Trunk:
   • Direct water to the root zone rather than the trunk to prevent fungal diseases and rot. Watering the trunk can also promote shallow root growth, making the tree more susceptible to drought stress.

Additional Tree Care Tips During Hot Weather

1. Pruning:
   • Limit pruning during hot weather to avoid stressing the tree. Remove only dead, damaged, or diseased branches.
   • Avoid heavy pruning, which can reduce the tree’s canopy and increase exposure to sunlight, leading to increased water loss.
2. Fertilisation:
   • Avoid applying fertiliser during hot weather, as this can increase water requirements and stress the tree. Fertilise in early spring or late fall when temperatures are cooler.
3. Pest and Disease Management:
   • Monitor trees regularly for signs of pests and diseases, which can exacerbate stress during hot weather. Look for symptoms such as wilting, discoloured leaves, or unusual growths.
   • Apply appropriate treatments promptly, following integrated pest management (IPM) principles to minimise chemical use.
4. Protection from Sunscald:
   • Young and thin-barked trees are susceptible to sunscald, which occurs when intense sunlight damages the bark. Protect trees by wrapping the trunk with tree wrap or using white latex paint diluted with water.
5. Wind Protection:
   • High winds can increase water loss and physically damage trees. Provide windbreaks using barriers or plantings to reduce wind exposure.

Special Considerations for Container Trees

• Container-grown trees are more vulnerable to heat stress due to limited soil volume and increased exposure. Water container trees daily during hot weather, ensuring thorough saturation of the root ball.
• Move containers to shaded areas during peak heat to reduce stress, and consider using larger pots to provide more soil volume and insulation.

Proper care during hot weather is crucial for maintaining tree health and promoting growth. By understanding the specific needs of different tree species and following best practices for watering, mulching, and overall care, you can help your trees withstand the challenges of high temperatures and thrive in your landscape. Consistent monitoring and timely interventions will ensure that your trees remain resilient and vibrant, even during the hottest months.