Saturday, August 04, 2018 1:00 am
Roadside trees often lack water when new
Question: I see newly planted trees around the city that appear to have dead growth at the tops of the trees. I've also noticed large mature trees with the same dead growth at the top. Will they be OK?
Answer: Anytime there is dead growth at the top portion of a tree, there is usually a cause for the dead growth at the base of the tree – the root zone – or in the lower trunk of the tree.
Many times trees planted in medians or park strips are LTTOD trees – left to their own devices after planting.
If the young trees are planted in spring followed by a summer drought, then there just isn't enough water in the soil to support the top of the tree. Hence you observe transplant shock as it is often called.
Most newly planted trees need at least an inch of rainfall per week during their young lives to do well. This translates to about 10 to 15 gallons a week during a summer drought per tree. Some cites have developed maintenance programs for LTTOD trees so they are cared for by volunteers during their formative years. These programs can save money by reducing replacement rates for newly planted trees.
Sometimes improper tree planting also results in top death of branches. If the root flare of a tree is buried below grade by deep planting or volcano mulching, then the tree will suffer with top death, especially after the second or third year of growth. This is because circling roots develop at the buried flare and slowly strangle the tree over time.
Over watering young trees also results in crown death of trees. Newly planted trees in heavily irrigated lawns often will suffer. Homeowners sometimes will kill a young tree with kindness by watering the tree too frequently, even in periods of adequate rainfall.
The technique of using a large auger or screw to dig a hole for a tree is used by many tree planters. This problem with this technique is that the sides of the dug hole are perpendicular to the soil surface. The preferred hole for planting tree should be a half moon in shape. In heavy rainfall periods or in irrigated areas, one can see how the water enters the hole and stays there for a considerable time. The roots rot in the flooded conditions, and the trees develop top death and many times die completely.
Large trees, especially native hardwood trees like oak, hickory, and maple, experience die-back of branches in response to disturbance of the root zone. Often one sees the damage appear within a year or two of construction and soil compaction. Maybe a sewer line was installed, or maybe a home addition or garage was constructed over the root zone.
There are other reasons for top death of trees. Insects or diseases can also play a role. However, often it is what we do as tree planters and caregivers that results in top death or mortality of trees.
The Plant Medic, written by Ricky Kemery, appears every other Saturday. Kemery retired as the extension educator for horticulture at the Allen County branch of the Purdue Extension Service.