Why are my Maple Tree leaves getting smaller?

As we, the Arborists at Schneider Tree Care, are out on your properties day after day we often see patterns develop.  We discuss these findings with each other because of our love for trees and our desire to help you by gathering information.

We have lots of maples growing in our area. And while they are generally a hardy, native tree they can also have their share of problems.  One symptom of many potential problems is a smaller than normal leaf. We have brainstormed and created the following reasons your maple might be producing smaller leaves than it has in years past.

Scale insects – Many maples have scale insects on their trunks, limbs, twigs and leaves.  Sapsuckers take advantage of this and feed on them.  You will often find holes in the trunk where they’ve been.  As the insects excrete honeydew from the phloem they’ve ingested from your tree, and as the holes weep phloem from the sapsuckers holes, your maple’s trunk turns black.  This is not harmful, but could be unsightly and worrisome to homeowners.   The scale insect can cause injury to your leaves, however.  When feeding on young leaves scale insects can distort them and cause enough stress to make them smaller.  Once treated, any new leaves will be normal.

Lack of water or too much water – Many of the same symptoms occur when there is either too much or too little water available for your trees.  When trees lack water, they wilt.  When trees get too much water their roots can decay and stop taking water in.  So, the tree again lacks water.  Either of these things can cause the leaf on your tree to be smaller than normal.

Cold weather at leaf break – When the weather warms quickly in the spring and trees bud out earlier than normal they are susceptible to a late frost killing the buds or newly formed leaves.  When the tree has to regenerate those leaves, they may come in smaller the second time.  Be sure your tree has the proper nutrients available to it so it can replenish itself after the second effort to leaf out.

Girdling roots – The last thing most people suspect when they are concerned about the size of the leaves would be the roots.  Maples are especially prone to girdling roots.  A girdling root grows around the trunk of a tree up to the point of strangling it.  Normal movement of water and nutrients may be reduced or cut off completely.  This causes stress and decline and can often affect the canopy of your tree.  In most cases these roots can be exposed and removed.  Don’t be fooled into thinking that just because you’ve seen the tree living with a girdling root for many years that it isn’t affecting it.

Planting Depth – When trees are planted too deeply they face a tough life ahead.  Girdling roots can develop, the possibility of root rot is greatly increased, they grow more slowly and have a visible lack of vigor.  All of these stresses can lead to smaller leaves.

Nutrient imbalances and high pH – Just as humans need a balanced diet, trees need the same.  But sometimes they are planted in an environment that won’t allow them to pull the needed nutrients from the soil.  If you have fertilized and still have signs of nutrient deficiency such as yellow or distorted leaves you may have a soil pH that is too high.  Correcting pH isn’t easy or done quickly, but it can be changed.

Soil compaction and paving – This is always a consideration given our hard clay soils.  Soil compaction leads to less water available to the root system, which leads to less water available to the leaves.  The leaves become smaller and provide less photosynthesis to the tree which leads to stress and the opportunity for other problems to occur.

Soil compaction can be lessened by adding mulch to areas accessed by pedestrian foot traffic and equipment.  Corrective action can be taken by aerating, vertical mulching and airspading.

Grade changes (fill over 4”) – Raising the grade is very detrimental to your trees.  Air circulation to the roots is cut off.  Moisture and nutrients cannot reach the roots.  Drainage can be affected and in some cases drown the tree.  Bark decay is common where the additional soil touches the trunk.  If your tree survives the initial shock of additional soil, it will begin a slow decline and you will begin to notice smaller leaves each spring. 

Tree Growth Regulators – There are instances when it is advantageous for a tree to produce smaller leaves.  Trees that have been damaged by construction or are older and declining can temporarily benefit from not having a large canopy to support.  A tree growth regulator is applied around the base of the tree to purposely slow the growth of the tree for a few years and allow the root system to expand.  If your tree is planted next to a tree that has had a tree growth regulator, it might be ‘benefitting’ from this treatment.

Herbicides for your lawn (weed and feed) – Just as with the tree growth regulators, your tree might be influenced by the type of fertilizer you are adding to your turf.  Be aware that fertilizers that contain weed control can be absorbed by your trees roots as well.  Weed killers are herbicides and can cause stress in your tree.

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