Dave Butler joined the MANA community meeting on June 16 to share information about tree health. As we are all aware, our neighborhood is lucky to have a lot of large trees. Several large trees have fallen this year and many of us wonder: is there a problem and is there anything we might do about it? Dave gave a short presentation and answered questions from the audience.
Dave began by explaining that that MANA and the greater Druid Hills area are both experiencing problems with trees that are now 60+ years old as some of these trees are reaching the end of their natural lifespan. Another issue is that we have had a lot of droughts which cause damage to the trees' root systems. As drought or stress "prunes" the root system, the tree's footing also weakens. Last summer, we had a record number of extremely hot days. In a separate conversation, Dave also pointed out an issue specific to our neighborhood: our soil is generally quite shallow, especially at the ridges, so it dries out quickly during the summer and does not support the trees very well when we have strong winds and already weakened root systems. The area around Woodridge Drive at Alberson Court, Gardenia Lane, and Whelchel Drive is a good example. A lot of trees have fallen there lately.
What can homeowners do to protect their trees? One key thing is to ensure the tree receives sufficient water. That may mean watering during dry spells, but also routine measures to ensure that the tree is not losing water unnecessarily, whether to competing plants or the atmosphere as the ground dries. Dave used a different illustration during his presentation, but made all the points illustrated below:
1) Know your tree anatomy: the tree's root system extends beyond the visible crown of leaves.
2) Arborists suggest using
mulch at least to the drip line (the periphery of the tree's crown). But note that the root system extends well beyond the crown's width. Try to mulch as close as you can to the drip line.
2a) Mulch well but
do NOT pile mulch all the way to the tree trunk. That invites excessive moisture retention and can lead to rot; rot opens the way for insects and disease.
3) Trees need water. They use water as part of their metabolism but also lose water due to evaporation, more so when air is dry and hot. The "rule of thumb" for dry spells is to water 1" per week. That means the amount of water it would take to cover the intended area to a depth of 1". If you don't want to measure and calculate, a good rule of thumb is to dig into the soil; if it is moist to ~4" below the surface, your tree is sufficiently watered.
3a) It's better to
water deeply even if you water less often. Shallow watering encourages roots to remain near the surface. That translates to a higher percentage of root mass becoming dehydrated in dry conditions and a tree that has limited ability to "drink long and deep" when water is available over longer periods. A top heavy tree is not a stable tree.
4) Remove English ivy (
Hedera helix) from tree trunks and bases. [
Tips for removing ivy: "shoulders and ankles"]
If we have a villain in the neighborhood, it is English ivy. Although it can make a great ground cover if strictly controlled, English ivy can be very damaging to trees. When it covers a tree's base and trunk, it hurts the tree in several ways:
(1) ivy roots compete with tree roots for water and nutrients and
(2) the leaves reduce air circulation which can encourage bark damage. At first blush, it may look like ivy acts like a "living mulch" but the net effect is to the tree's detriment: less water and fewer nutrients for the root system, and the risk of bark rot which invites fungal and insect damage. A tree's bark is much like our skin: damaged tree bark is the equivalent of an open sore.
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As long as ivy remains on the ground, maintenance is ongoing. These pines were cleared of ivy from ground level to shoulder height. The white arrow points to a ~4" severed ivy "trunk".
12 months later, dead ivy tendrils still cling to the trees, and new growth is covering the breach from the ground up (in this case, 4+ feet of growth in a year). |
Just when you thought ivy couldn't make any more trouble, we come to ivy's secret agenda: reaching sunlight because only when it grows to the tree canopy will it be sufficiently mature to bloom and produce seeds. The seeds are eaten and dispersed by birds, far and wide.
(3) If you allow ivy to work its way up a tree, through the years, it will produce vines that are as thick as a man's arm. And with that goes a lot of foliage very high off the ground. The result is an artificial "thickening" of the tree's natural canopy by leaves that are not shaped to the tree's advantage. That means
(5) that your tree now has an ivy "sail" that catches a lot of air and possibly ice. 1 + 2 + 3 + 4 + 5 = a top-heavy tree with possibly rotted trunk/limbs and a weakened root anchor. Add high winds or ice storm buildup and what's a tree to do but surrender to gravity?
In evaluating a tree, an arborist completes a multi-point checklist, however, Dave said homeowners can look for some obvious signs of trouble:
1) Starting with the base, remove any vegetation and look for the presence of mushrooms. Mushrooms are fungal fruiting bodies and reflect damage to roots or bark because fungi feed on already-decaying wood.
2) Check the canopy in summer: you should see lots of healthy leaves and branches. If you see a lot of bare/dead branches in the upper canopy, that is not a good sign.
An audience member asked about pines--what are signs of trouble? Dave said it will be similar: look for cracks or cavities in the bark, excessive browning of foliage. All trees lose leaves/branches naturally but any time you see excessive browning out of sync with the season, you should explore further.
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N.B. Some of the above information was not part of Dave's presentation at this MANA meeting, but has been shared over many years of service to our neighborhood via his work at the Clyde Shepherd Nature Presearve, the community garden, etc.
