BEST GIFT FOR TREES IS A GOOD SOAKING

Spring 2005 produced a high incidence of anthracnose, a fungal disease that affects ash, bur oaks, maples, elms and other hardwoods. Anthracnose is common during stretches of cool, wet weather like we experienced in late spring and early summer.

Although anthracnose doesn’t kill trees, it weakens them by forcing trees to produce new leaves to replace the brown, mottled, blotchy leaves that are unable to photosynthesize light into energy reserves for the tree’s root system.

Producing new leaves is not a problem for trees when plenty of soil moisture is available to fuel replacement leaf production. During periods of drought, however, trees become stressed as soil-moisture reserves disappear. The intense heat and lack of rain in July and early August put many of our landscape trees in a high-stress condition. This is not a good situation for trees to be in as they transition to the winter dormancy period. Stressed trees are susceptible to a variety of maladies: insect predation, disease, and cold-weather stress caused by deep-frost penetration in the absence of snow cover.

I answer many phone calls each growing season from tree owners who describe a specific problem and want me to tell them a single cause and solution for the problem. On a few rare occasions, there may be a single cause/solution for a problem.

More commonly, however, the cause of a tree problem is multi-faceted. The problem might have begun with improper planting, followed by a tree being stressed from anthracnose, followed by a summer dry spell, and then further compounded by a severe winter with deep frost and a lack of snow cover. Add in a couple of unseasonably warm weeks in February that confuse a tree in dormancy and the result is a tree that is suffering from a whole bunch of maladies.

Homeowners don’t have a very long list of prevention tools to help trees stay healthy. Of the tools that are available, water is clearly the most important. Tree roots need to enter into the winter-dormancy season with plenty of soil moisture.

Mature trees must fend for themselves when it comes to moisture. It is not practical to deliver thousands of gallons of water on a weekly basis to the entire root zone of a 100-year-old oak or maple tree.

Young trees are a different matter. The best way to help young trees prepare for winter, and to replenish moisture in the root zone, is to water trees with a deep soaking once a week right up until our first hard freeze.
The most critical trees to water deeply once a week are conifers (evergreens). This is because pine, spruce, arborvitae and other conifers don’t shed their leaves in winter like deciduous trees. Conifers continue to transpire (give off moisture) throughout the winter months even though they are unable to take up soil moisture when the ground is frozen.

If you have spruce, pine and other conifers in your yard, my advice is to water them liberally between now and late October. Conifers that have adequate moisture in their root systems during winter are better able to resist disease and insect predation come spring.

A common moisture-stress condition that is evident most years in August and September is premature coloration on maple trees. Maples should not exhibit yellow, red or orange leaves in August and early September. Maple leaves that turn early are a signal that these maple trees are suffering from moisture stress.

Many stressed maple trees are planted in lawn sites where the maple’s shallow root system competes with turfgrass for soil moisture. Many of the maples planted along streets and in boulevards where soil is compacted are also severely stressed during drought. Many of these maples will die prematurely from “maple decline” brought on by root damage from deep-penetrating frosts, summer insect invasions, diseases such as anthracnose and verticillium wilt, and other secondary invaders.

As with evergreens, maples -- particularly maples growing in turfgrass -- will benefit from a weekly soaking right up until the first hard freeze.

Occasionally a tree problem has a simple solution. More commonly a problem is the result of a handful of inter-related causes and doesn’t have a simple solution.

Here’s the bottom line: the single-most important management strategy to help trees stay healthy is to make sure tree roots have adequate moisture as winter approaches.