Help! My Tree's Leaves Are Turning Brown: A Guide to Common Problems

Noticed something off with your tree? Maybe some brown leaves? It can be frustrating when plants don’t establish well. Common symptoms include yellow or brown leaves. Don’t worry, most of these issues can be fixed with a little TLC and don’t necessarily mean you will lose the plant. Often, environmental factors like watering, drainage, and wind are the culprits. Let’s walk you through some common problems and how you can help your tree thrive!

Common Problems and How to Address Them

1. Brown Leaves

• Causes: Drought, wind damage, or waterlogging.
• Solution: Ensure consistent watering, protect from strong winds, and check soil drainage.
• No Need for Concern: Brown leaves on deciduous trees are part of the natural process of change in the autumn, as seen in species like Hornbeam or Beech.

2. Yellow Leaves

• Causes: Nutrient deficiency or overwatering.
• Solution: Apply a balanced fertiliser and adjust watering practices as needed.
• No Need for Concern: The occassional yellowing leaves on evergreen trees are often part of the natural leaf renewal process. Deciduous trees like field maple may also turn yellow in autumn as part of their natural cycle.

3. Powdery White Coating on Leaves

• Causes: Powdery mildew, a fungal infection that often develops in warmer, humid conditions with poor air circulation or overwatering.
• Solution: Improve airflow, increase light and sun exposure, and avoid overwatering. If the problem persists or is very widespread, apply a fungicidal spray specific to powdery mildew.
• No Need for Concern: Common in late summer and autumn, small patches of powdery mildew are typically cosmetic, generally only affecting the tree's appearance and not its long-term health.

4. Non-flowering

• Causes: Pruning at the wrong time, poor light conditions, or stress.
• Solution: Avoid cutting flower buds during pruning and ensure the plant gets enough light and nutrients. When pruning, be cautious not to remove flower buds, especially if you’ve chosen a plant for its attractive flowers or berries. Cutting these buds can reduce or eliminate the plant’s ability to produce flowers or fruit in the upcoming season.

5. Wind Rock

• Causes: Unsecured trees can suffer from wind rock, which can damage roots and lead to water collecting in the ‘socket’ created by the stem moving at soil level. This can lead to fatal rotting.
• Solution: Staking helps avoid this issue. Avoid overly tight tree ties when securing stems to stakes, prevent rubbing, and remember to progressively slacken the ties as the stems grow.

5. Stem or Branch Damage from Over-tight Ties

• Causes: The trees are attached to the pleached frame using small black zip ties for training purposes. If left on too long without monitoring, they could cause rubbing and damage.
• Solution: As your tree matures, ensure that any overly tight training ties are removed or replaced as necessary to prevent them from cutting into the tree’s trunk or branches. During the first season or two, regularly tie in the branches to get them used to the shape of the guide frame. The tree will also have a central thick bamboo cane to help train the straight, clean stem. Monitor these ties and adjust them as needed.

6. Minor Splits, Cracks or Blemishes in Stems or Branches

• Causes: Natural growth, environmental factors such as wind, fluctuations in temperature, or humidity changes. Minor damage can also occasionally occur due to handling during transport or planting.
• Solution: Most trees will self-heal with proper care, including adequate watering, fertilisation, and protection from extreme conditions. However, monitor the affected areas for any signs of infection, such as fungal growth or pests.
• No Need for Concern: Minor splits are usually cosmetic and unlikely to affect the tree’s long-term health. During the dormant season (October to April), the tree will slow its growth and use this time to strengthen and repair naturally.

You’ve Got This!

Pleached trees are living plants that require care to thrive. While we work with experienced growers to give them the best start, the ongoing responsibility for their health lies with you, the customer. Proper aftercare is essential, especially during the first few years after planting. By following this guide and taking proactive steps, you can ensure your trees establish well and remain healthy.

For more detailed advice on these issues, please refer to the RHS guides on:
Brown Leaves on Woody Plants
Chlorosis, or Yellowing, of the Leaves
Powdery Mildrew
Non-flowering Woody Plants
Establishment of Trees and Shrubs