Keep trees alive through the drought

The Tribune published suggestions for keeping your trees alive. Read the entire story here.

As SLO County residents scale back their landscape irrigation, trees — especially pines — have been put in danger of disease and death

By Stephanie Finucane, July 13, 2015

Brown lawns — or “golden,” as they’re been christened by some PR campaigns — are cropping up in many California neighborhoods. They may not be pretty, but they are a sign that water conservation has become a way of life in drought-stricken California.

Unfortunately, trees — which are much more precious and harder to replace than turf — also are falling victim to drought.

Pines are especially vulnerable; the drought leaves them in a weakened state, when they’re more susceptible to bark beetle infestation. Other trees are at risk, too.

“We’re seeing a significant amount of mortality, primarily in pines, but (also) die-back and stress in oaks, countywide,” said Dan Turner, former county fire chief and current business manager for SLO County’s Fire Safe Council.

With so many dead trees, fire is a big concern, especially in heavily forested communities, but there are other worries as well.

Trees provide a host of benefits that make them worth saving — not the least of which is improving air quality. Trees, as we all learned in science class, store carbon dioxide, absorb other pollutants and emit oxygen. Without them, air quality would suffer.

Trees also are good for our bottom lines.

Consider: Consumers are apt to spend more time in downtowns with tree-lined streets. Homebuyers are willing to pay more for houses with attractive trees in the yard. And by providing shade for homes, trees can cut down on use of air conditioning in warm regions.

They also make a hot day at the park a heck of a lot more enjoyable.

So how are our trees doing?

In terms of actual counts, at least 12.5 million trees have died in California’s national forests, according to aerial surveys conducted this year. The Sierra Nevada and Southern California have been hit particularly hard.

Closer to home, the biggest die-off has occurred in Cambria, where an estimated 40 percent of pines are dead or dying, though in some areas the percentage is as high as 80 percent to 90 percent.

Elsewhere in the county, the situation isn’t so bleak, though the drought has taken a toll.

In the city of San Luis Obispo, in normal rainfall years, around 15 or 20 trees are removed from city parks and streets because they’ve died of natural causes.

“This year, we (took out) more than 100,” said city arborist Ron Combs. That includes 68 Monterey pines removed from city parks.

Tree removal projects are in the works in other communities as well. The county’s nonprofit Fire Safe Council awarded several grants to fund removal of hazardous trees and brush in Cambria, Pismo Heights, Lake Nacimiento and Santa Margarita.

Other agencies are tackling the problem, too; county public works has taken out more than 165 trees in Cambria that could fall and block a road, impeding evacuations in case of fire.

PG&E has stepped up its inspections and is trimming or removing dead trees (as well as live branches) that pose a hazard to power lines.

Some of the tree removal is free of charge to property owners.

PG&E, for example, doesn’t charge property owners for removing or trimming trees on private property when it determines the growth poses a hazard to power lines.

However, as a general rule, property owners are legally responsible for the trees on their property, and they can be ordered to remove fire hazards, including dead brush and trees.

Tree removal can be costly — as much as $1,200 per tree or more.

That’s another reason it makes economic sense to help trees survive the drought.

“Long and deep, once a week,” is the watering advice that Combs, the city arborist, gives for clay soils. Trees in sandy soil may need more frequent watering; check the soil to best determine how often you to need to water.

One overarching point to keep in mind: Trees should be the first priority for outdoor watering. Golden-brown lawns can bounce back; dead trees can’t.

How to water your trees like Mother Nature

Water the drip zone: This is how nature designed trees to be irrigated. Rain hits tree leaves, cascades off the canopy like an umbrella and drips to the ground. That outer edge is the drip line where the strongest feeder roots gather moisture. More rain drips between branches and leaves under the canopy like a leaky umbrella; that’s the drip zone where more feeder roots do their work. Few feeder roots are close to the trunk; don’t water there.

Deep and slow: Water trees deeply and infrequently, once a week or less. To water deeply, water slowly and directly away from the trunk so soil can absorb the moisture. Make sure water reaches the tree’s feeder roots in the top 12 inches of soil.

Time it right: Water early in the morning or after sunset; that’s when trees naturally replace water they’ve lost to heat during the day. That also cuts evaporation.

The right way: Apply water directly to the drip zone with a hose on a gentle trickle, soaker hose, drip lines or buckets placed away from the trunk. Apply water in several places, spaced 2 to 3 feet apart, allowing the water to soak in. Try this: Take a 5-gallon bucket and puncture two or three holes in the bottom. Place the bucket directly on top of the soil under the tree’s canopy and fill with water. The water will slowly seep into the soil. Move the bucket and repeat until the root zone is irrigated.

Go deeper: In hard clay soils, auger holes 1 foot deep every 3 feet around the tree near the drip line. Fill those holes with compost, then water; that vertical mulching will encourage deeper root growth. Some arborists and landscape services also offer water injections, pumping pressurized water directly into the root zone.

Easy does it: Let up on pruning, fertilization and other normal maintenance that encourages tree growth. Prune only if absolutely necessary. Do not fertilize a tree under drought stress.

Mulch: Fallen leaves form natural moisture control and also break down, adding nutrients to the soil. Mimic that with mulch. Spread organic mulch (wood chips, bark, straw, shredded leaves, pine needles, compost, etc.) in a circle around the tree, 2 to 4 inches thick and at least 3 feet out. Spread mulch like a donut, not a volcano. Leave a 6- to 8-inch circle clear around the trunk to avoid rot. Avoid rocks as mulch; they absorb heat, stress roots and increase a tree’s water needs.

Eliminate competition: Remove the lawn growing directly under the tree and replace with bark or other organic mulch.

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