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Trees in Drought, Part 2: Care

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Trees in Drought, Part 2: Care

by Ellen Solomon

This week I saw a neighbor had removed her lawn and installed sheet mulch - cardboard covered with wood chips. She left standing a beautiful mature willow tree. What will happen to this tree in the drought?

In my last article I discussed different elements of how to care for a tree in drought: tree species and their degree of drought tolerance, location of roots, and soil conditions. In this article I will give you a more hands-on, practical approach to keeping your trees, watering your fruit trees and high-water trees, replacing with drought-tolerant species, and sustainable practices: observing your tree, mulching and using “freewater.”

If my neighbor wants to keep her willow or other “high-water tree” alive, she has to water it, but not like a lawn. Trees and lawn require different watering and should always be set up on separate lines, because lawns need frequent shallow watering, and most trees need infrequent deep watering. Water the tree where the roots are growing: at the drip line and beyond.

To determine how dry the soil is, use a soil probe or dig down 6 to 18 inches. If the soil is dry - you will know for sure that your tree needs added water. 

When actively growing in early spring after an adequate winter rainfall, trees don’t need much water, because they draw on soil water stored from the winter. In late summer high-water trees need twice a month deep watering at a minimum. Be attentive to the appearance of your trees. When leaves and branches droop, they reflect inadequate water. 

Native, Drought-Tolerant

Native, drought-tolerant trees, such as coast live oak or black oak, have evolved with adaptations to survive dry summer conditions of four to five months. This assumes that winter rains have recharged deep water sources. If established, such trees do well June through September with no added water. Starting October if there is no rain it is good to water deeply once a month around the drip line or beyond. 

Replacing With A Drought-Tolerant Tree

If you have removed your lawn and your thirsty tree has died, but you want some shade, plant a drought tolerant tree like African sumac, acacia or California native oaks.

The best time to plant is in the fall, so that the roots can become established during a rainy season and while the days are shorter. The next year you will need to water the tree every few weeks during the dry period, by watering around the drip line. But be careful not to overwater. When it is hot and the roots have too much water, fungus can grow in the soil and kill your tree. Plan to organize your garden so that drought tolerant plants are in the same area for ease of watering.

Proper planting is important! Prepare the soil twice the width of the root ball. Be sure to pull apart the roots; do not plant a root-bound tree. And plant high; the soil will settle. You may want to have a Certified Arborist supervise your landscape crew. If your tree is not planted properly, in a few years it will need to be replaced.

Fruit Trees

Fruit trees are a special case. You can find excellent information from UC Davis prepared for stone fruit commercial orchards (peaches, plums, nectarines):  “... certain stages of growth are less sensitive to drought stress.”  They recommend reducing watering after harvest. They also offer information on fruit trees’ survival with little or no irrigation water by using a severe pruning technique.  [ucmanagedrought.ucdavis.edu/Agriculture/Crop_Irrigation_Strategies]

Mulch

All trees will benefit from a deep layer of organic mulch. Be careful not to pile it against the trunks of the trees. Mulch will retain soil moisture, and break down over time to improve the soil with nutrients and organic matter.

Trees And Ivy

Some beautiful trees are surrounded by a green carpet of ivy. Ivy will steal water and nutrients that are intended for your trees. Some ivy even settles its feet into the tree bark and draws out essential liquids from it. Ivy is a treacherous companion for trees, with or without the drought.

Freewater

In this time of increased awareness of earth’s environment and limited resources - from reducing plastic waste to driving less and reducing carbon dioxide - we can also rescue our gardens and fruit trees by using freewater: previously invisible water wasted, such as catchment of roof runoff, shower water before it gets hot, and vegetable washing water. Your buckets of reclaimed water might save your tree! 

 

Tree wise; water wise; earth wise!

 

Written by Ellen Solomon, Certified Arborist and Horticulturist. She is owner of North Bay Horticulture and advises on all aspects of gardening to help create beautiful and healthy plants and garden spaces.

Copyright 2014 by Ellen Solomon