Seeds

Debbie Arrington digs into gardening news

Seeds: Trees need extra TLC during drought

08/23/2014 12:00 AM

08/22/2014 11:14 PM

Walk down almost any residential street in Sacramento and you’ll see the cumulative effects of this dry, dry year. Often in the middle of a brown lawn stands a very sad, droopy tree.

Once drought restrictions are lifted, the lawn can be renewed or replaced in a matter of weeks. But the tree? It took decades to grow that size. Any replacement will need several years to reach that same potential shade and stature.

Certified arborist Matt Morgan of Davey Tree Expert Company has seen the toll on his daily rounds in Sacramento. Coastal redwoods look crisp around the edges. Birches have gone golden or dropped their leaves altogether.

“Tulip trees are starting to get stressed out as well,” Morgan said. “Browning is a big issue. The oaks and native sycamores are still doing really well, but they’re native trees. They were made for drought.”

Morgan is particularly concerned about lawn trees, those trees that were planted in the middle of turf that right now may not be getting watered.

“Trees get used to that extra water,” he said. “So when that water is cut back, it will take a toll. You can gradually wean it back slowly. One of the worst things you can do is tear out everything but the tree and suddenly go to a (low-water) xeriscape. The lawn is gone, but the tree will be gone, too. You need to make the (irrigation) transition gradually.”

This summer, readers have sent a steady stream of pleas for our urban forest. They’re worried about the health of their big leafy friends.

“Sacramento Valley’s canopy of trees is the pride of our area,” wrote Penny Blalock of Sacramento. “Because of the extent of the drought we’re enduring and its anticipated duration, are we in jeopardy of losing mature as well as relatively young trees in Sacramento due to a prolonged lack of adequate water?”

Two years of drought definitely have taken a toll, say experts. Even after normal rainfall starts again, these trees and shrubs may suffer from drought for many years to come. It can take up to three years to see the full effects of the damage.

“Trees take a long time to grow and a long time to die,” said Sacramento Tree Foundation’s Anne Fenkner. “You may not see the negative effect immediately, but there will be consequences.”

The solution is to concentrate drought relief on trees that are most susceptible. Even if you stop watering your lawn, make sure trees get sufficient moisture.

Trees have deep, widespread roots for a reason; they’re big. They need the most water.

“Yes, they take a lot of water, but they give the greatest benefit,” noted Fenkner. Shade and cleaner air top that list of benefits, but trees also offer several social and public health benefits.

Fenkner leads tree tours of Sacramento’s McKinley Park. She’s seen firsthand the evidence of drought.

“The coastal redwoods are really showing signs,” she said, “but we’re seeing it in all the trees. Fall color is coming on. Seasonally, temperatures aren’t reflecting autumn; it’s still quite warm. The stress is showing by the reduction of chlorophyll.”

Determining exactly how much water a tree needs is dependent on many factors from species to soil type. Young, immature trees – especially those planted within the past three years – are at greatest risk. Their roots aren’t deep enough to fill their water needs.

Newly planted trees with a trunk under 2 inches in diameter need at least 5 gallons a week; make it 10 to 15 gallons if the weather hits triple digits or or is very windy.

Larger trees need significantly more irrigation. A mature maple with a 30-foot wide canopy requires 500 gallons or more a week.

To make sure a tree is getting enough water, look at the soil. Poke a long screwdriver or rod into the dirt; if it’s hard to push in, the water may not be reaching the roots. Or take a spade or trowel and dig down 6 to 8 inches. Is the soil dry and crumbly? It’s time to water.

Ideally, the root zone should be irrigated 8 to 12 inches deep no more than once a week for thirstier trees; once a month for more drought-tolerant varieties.

Water trees very slowly so the moisture can trickle down into the ground. Ideally, run a soaker hose around the diameter of the tree a foot beyond its dripline, the edge of its canopy. Or use a bubbler or the garden hose with the water turned on very slow.

Or try the “drip bucket” method. Take a 5-gallon bucket and poke two nail holes in the bottom. Place the bucket on a flat spot within the tree’s dripline and fill it with water. Once it’s empty, move it to the other side of the tree and repeat. Keep moving and filling the bucket until the tree’s root zone has enough moisture.

“What can you do to help your trees? Mulch, mulch, mulch,” Fenkner added. “Remember the ‘4 by 4 by 4’ rule: Keep the mulch 4 inches from the trunk, 4 inches thick, 4 feet out.”

Use organic mulch such as shredded bark or wood chips, not rocks or shredded tires, she said. “Organic mulch is the best thing. Rocks reflect heat; there’s the potential of sunburn to the tree. The beauty of organic mulch: It decomposes and provides micro-nutrients to the tree. It’s like slow drip feeding.”

That helps the tree stay healthier, too, and cuts down on stress.

“Watering a tree is a lot easier than watering the lawn,” Morgan said. “My fear is next year. Trees are under stress right now, but next year we could have significant losses (if the drought continues).

“A tree can only undergo stress for so long. We need to help our trees where we can.”

About This Blog

Debbie Arrington is the home and garden writer for The Sacramento Bee. A lifetime gardener and consulting rosarian, she took over that beat in 2008 after almost 10 years on The Bee's Sports staff. Debbie also writes about food and cooking, focusing on seasonal crops and farm-to-fork cuisine. Reach her at darrington@sacbee.com or 916-321-1075. Twitter: @debarrington https://twitter.com/debarrington
 

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