The Gardener's Corner
Trees also need love
By Judith Rogers

We had a hot and very dry growing season this year which triggers concern for the welfare of our trees.

Short term distress from heat and drought is evident by the wilting of leaves, scorch, and some exfoliation. Some trees respond to the lack of adequate moisture and heat by shedding their leaves while still green, until the tree is able to rebalance the foliage to the available moisture.

Other trees will hang onto their leaves but experience root die back from the lack of moisture. The leaf tissue farthest from the vein will dry out, turn brown and die. The hotter and drier the weather remains, the more of this leaf tissue is killed. Leaf scorch is the term to describe the appearance of leaves that are only partially alive, due to this excess drying out. Scorched tree leaves can be confused with anthracnose which occurs in wet weather.

Long term distress happens over several years of drought and can cause stunted growth, branch die back, vulnerability to pests and diseases, and possible death. Stem die back is caused when the fine feeder roots after searching beyond the canopy of a tree for moisture and finding none, may die. Even though water could become available after their loss, this tends to reduce the size of the canopy of the tree. Many trees and shrubs can take as long as three years after severe drought to display negative effects.

Here's what you can do to help your trees. If supplemental water was given in spring and early summer to young trees they should have been fine through the growing season while mature, established trees are generally able to manage on their own. However, be sure to water trees planted last thoroughly, before the winter hardening of this year's growth. Even your mature woody plants after the drought we've had will benefit from some water before the ground freezes by adding moisture at least 22 to 30 centimetres deep. If planted in clay, which does not absorb water as quickly as sand, apply it slowly to reduce runoff. The whole idea is to water deeply but not frequently to encourage the roots to grow deep and hunt for water other than at the surface. The use of drip or soaker hoses around trees by the drip line is a good method. Or, if using the garden hose, place it by the drip line in a couple of spots with only a trickle coming out until watered well.

Mulch in the form of shredded bark or wood chips at no more than five to six cm thick will help keep moisture in the soil for tree roots. Avoid the mistake of building mulch volcanoes around the trunks of trees which can trap too much moisture in the root zone and cause root rot. And, piling lots of mulch against the trunk can lead to insect, disease and rodent attack on the bark. Also, matted mulch can prevent movement of air, water and nutrients to the soil below so give it an aerating fluff with a garden fork.

The needles on evergreen trees live from one to several years and are lost through an inner needle drop or third year drop. In spring with new green growth, the preceding year's needles lose their colour as their role in photosynthesis is over. Late September or October is when these needles will drop off, depending on the variety of tree and the amount depends on the condition of the tree and the previous growing seasons. If the current year's growth is vigorous, the health of the tree is not a concern. Evergreens need to be watered well right up until the ground freezes as moisture will continue to evaporate from the needles over winter. Experts predict imminent stressful conditions for trees such as we faced this year so monitoring rainfall and supplying supplemental moisture will become our responsibility to ensure their future.

One tree can absorb the carbon dioxide from four cars a year.