You've done your homework by assessing your yard and using the information to choose the right trees for the situation. You plant them in the proper way and work hard to water, prune, and fertilize them as needed. Even with the best of care, though, trees can still become sick. Here are some things to look for when assessing whether your tree is healthy:
Only One Central Leader (For Most Trees)
Most landscape trees should be pruned to have only one central leader. This will add strength and to stability to the tree structure, as well as create a straight appearance. If there is more than one leader, it may eventually cause the tree to split. Exceptions include:
- Some fruit trees (namely peach, nectarine, cherry, and plum, among others)
- Trees with several trunks (each should have one main leader)
- Some topiary and bonsai forms, such as an espalier
Evidence of Yearly Growth
Trees produce new growth yearly on both their trunk and their branches. You should look to see how much growth has occurred in the past year by checking the distance between this year's buds and last year's (evidenced by scars on the branch). The average growth varies by the tree, so check to see what you should expect.
No Dead or Broken Branches
Prune away dead and broken branches as soon as you see them, as these are a common way for insects and diseases to enter the tree. Test for dead branches by scraping the branch with your thumbnail. Living branches will show green underneath. You can also test branches by gently bending them. Living branches will be supple and bend easily. If the branch is dead, it will snap.
Check the Trunk
With the exception of certain trees (such as some birches, eucalyptus, and maples), the bark should not be loose or peeling. There should not be fungi growing on the trunk. Be careful when using garden equipment around trees, as damage to the trunk can leave an open wound where insects and diseases will attack. There should not be large cracks or holes.
No Bare Patches
If you have an evergreen tree, watch for sections without leaves year-round. Otherwise, don't worry about your deciduous trees until the leaves have appeared in the spring. Common causes of bare patches include:
- Nutrients and water not reaching those branches
- Animals eating the leaves
- Improper pruning practices
- Pesticide damage
- Insects and diseases
When a tree is stressed, a common sign is wilting. The leaves and stems will lose their rigidness and begin to droop. Some of the causes include:
- Lack of water
- Too much or too little sun
Proper Leaf Color, Shape, and Size
A good indicator of poor tree health is the leaves. Make sure they are the right color for the season you are in. Unless the tree naturally has yellow or variegated leaves, be especially wary if they turn yellow. They should not be stunted or irregularly-shaped. These all can be signs of nutrient deficiencies, insect damage, watering problems, pesticide damage, and diseases.
No Signs of Insects or Diseases
Other causes of poor tree health include insects and diseases. Some warning signs to look for are: