How healthy is my tree?
Healthy Green Ash tree
The Johnson County Extension office gets a number of questions each year about the health of the inquirers’ beloved trees. Questions range from what’s eating on the leaves to why have branches died. Because trees are such a long-term investment, we want to help ensure that they will be around for a number of years. So how do we know if our tree is healthy? Ward Upham, horticultural specialist with K-State Research and Extension, offers some easy tips for determining tree health.
One of the most important clues in determining the health of your trees is the amount of new growth it produces. A healthy tree should have a minimum of 4 to 6 inches of new growth each year. Check branches whose tips are on the exterior of the tree crown, the ones in direct sunlight, not the interior branches that are shaded by the tree itself. Anything less than 4 inches on the majority of branches suggests the tree is under a great deal of stress.
So how do you tell where the new growth stops? Look for a color change in the stem. New growth is often greener than that the previous year’s growth. There is also often an area of what looks like wrinkled, compressed growth, where growth transitions from one year to the next.
Lastly, look at leaf attachment. Leaves are only produced on the current season’s growth. Therefore, new growth stops where leaves are no longer attached directly to the twig but to side branches. However, pay attention, as leaves may appear to be attached directly to last year’s growth but are actually born on short spurs. If you look closely, you can tell the difference.
All of these clues tell you whether a tree is under stress or not. It does not tell you what is causing poor growth. This year, the most common cause, by far, is environmental stress caused by the warm, dry winter of 2011 – 2012, and the drought and hot summer temperatures the previous two summers. Those conditions often resulted in damaged root systems. In some cases, root systems were damaged enough that those trees may struggle as we enter summer. Though the roots were able to keep up with moisture demands during the cooler spring weather, they may not be able to as temperatures rise. Such trees may suddenly collapse and die, or slough off branches they can no longer support. If possible, water to a depth of 12 inches every couple of weeks if we do not receive rain, in order to avoid further stress.
Keep in mind that 4 to 6 inches of growth is a minimal amount of growth. Some very vigorous and well cared for trees could push 2 feet or more of growth in one season. This is ideal for younger trees that we are wanting to mature as rapidly as possible. Older, mature trees will have less growth.