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Published November 15th, 2017
Taking care to prevent damage to (and from) trees
This rotted tree had potential of toppling nearby powerlines. Photos Pippa Fisher

With last winter's considerable rain following three years of drought, many large trees toppled, causing considerable damage throughout the Lamorinda area. Homeowners and residents are anxious to know what measures they can take to prevent more of the same this year.
According to a pair of arborists interviewed, the bad news is that it may be too late to save your tree, and it will take swift action to save your - or your neighbor's - house.
Once signs of disease or decay appear above ground, the damage to the roots may have progressed too far and cannot be undone.
Certified arborist Thomas Raeth, with Lafayette Tree and Landscaping, gives a list of some of the practices that can lead to disease: "When we have a drought and people cut back on water it can manifest stress in different ways. It may take time for trouble to develop."
While conserving water is necessary, mature trees need to have deep watering to maintain their health, says Raeth. "Pines are a good example. The drought stretched their health, allowing beetles to invade and consume the trees."
Raeth cautions that when mulching trees, it's important to use properly composted chips. "People cut down trees because they're diseased, and if you put those chips back on the ground without sterilizing them, the disease goes back into the ground." Also, if the chips are fresh, they use up nitrogen to decompose, depriving your trees of nutrition. Proper composting can take up to two years, with temperatures needing to reach 400-500 degrees in the pile.
A common mistake is pruning while the sap is active in the tree. The best time to prune is from December to February.
Another error is leaving the stake from the nursery attached to a newly planted tree. A new stake should be placed at least 6 inches from the tree, allowing for wiggle room. "The movement of the trunk stimulates the tree to strengthen its roots," says Raeth. When the tree is sturdy enough to support itself, the stake should be removed.
Homeowners should also avoid letting ivy or other vines crowd out the stump and climb the tree. Clear away shrubs or vines from the base of the tree and pull down parasitic vines.
John Traverso, certified arborist and owner of Traverso Tree Service in Saranap, recommends a visual inspection to detect potential problems. He warns, however, "Looking for something and having the knowledge to know what you're looking for are two different things."
Included in his visual inspection are the shape of crotches; elongated, poorly tapered branches sticking out of the canopy; heavy leans; cracks in the soil or uplifting and mounding on the backside of a lean; and fungal brackets on the lower trunk.
Traverso recommends periodically measuring the lean of a tree with a level to find out if the angle is getting worse. "Bark compression or folding on the leaning side of the tree along with bark separation on the backside indicates trouble."
Another indication of decay can be holes made by birds. He says, "The birds are making use of an already existing cavity, which means decayed wood already exists inside."
Traverso recommends pruning and/or crown reduction to mitigate some problems. Poorly tapered limbs are highly prone to failure, especially if decay is present.
Fungal growth on trunks and mushrooms around the base of a tree can indicate compromised wood tissue and shouldn't be ignored. This can also be an indication of too much water (e.g.: putting the tree on a lawn watering schedule throughout the summer).
While old, diseased trees may need to be removed, here are some tips for raising a new one:
1) Pick a tree appropriate for our conditions.
2) Remove decayed trees and roots from the planting site and use composted mulch to top dress. Traverso states, "Healthy raw material such as tree chippings, especially those with leaves and carbon materials mixed, tends to bring to life the process which benefits the soil and trees in the long run."
3) Do not water too often. Native trees prefer deep watering during the winter months. If subjected to a dry winter, supplemental irrigation should be applied in February through March for most trees, especially oaks, and not in summer.
4) Fertilizing should be performed in the fall or winter so nutrients can be processed and ready for absorption by the roots in the spring.
5) Use judicious pruning techniques in young trees to thin, shape and direct growth. Different trees have different demands and proper pruning methods are crucial, especially in the first few years.
6) Be mindful of the tree's drip line and allow for drainage. A tree's root structure is generally equal to or well beyond its growth aboveground.
When in doubt, call a certified arborist. Most will give a free estimate.

The split in the trunk of this tree reached all the way to its base.
A brave soul, in red, climbs the trunk of this rotted pine tree, cutting away branches to prepare to take the tree down. Photos Pippa Fisher

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