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Northern Gardening: Dryness, late snow cause brown pines and red spruce

Driving around town I have noticed many mugo pines and cedars with moderate to severe browning. Some of these trees and shrubs have shown no or only mild browning in previous years.
in the pines

Driving around town I have noticed many mugo pines and cedars with moderate to severe browning.

Some of these trees and shrubs have shown no or only mild browning in previous years.

A careful look at some Colorado spruce also shows the tips of branches turning red.

Except for some varieties of evergreens that are not fully hardy for our area, this degree of damage is unusual.

Contrary to popular belief, this damage to hardy evergreens is not caused by a cold temperatures, but rather likely by a combination of environmental causes.

Last summer we had an extended dry spell, and many trees were showing drought stress. This was more obvious in our deciduous trees, but evergreens were also affected.

If these trees did not receive sufficient supplemental water during this time of drought, they entered winter in a stressed, water deprived state. During the winter, wind and sun dry out the needles, which cannot receive any moisture from the roots in the frozen ground. The needles dry up and turn brown, or red in spruce trees.

This spring we still have snow on the ground, longer daylight, and lots of sunshine. The sun and the sunlight reflected from the snow add to the drying of needles. The radiation from the sun and reflected sunlight can increase needle temperatures considerably over air temperatures.

Moisture in the branches becomes exhausted because of the increased loss triggered by the warmer temperatures. This can cause entire branches to die.

What can be done to protect these trees and shrubs?

The best protection would have been provided last summer and fall with adequate water, and possibly burlap screens erected on the south and west sides of exposed small evergreens. This protection would shade the plants and prevent excessive moisture loss by the wind and sun.

Screens should be about one foot away from the plant. Please note that wrapping evergreens with burlap is not recommended because on warm sunny days the internal temperature will get too high. This high temperature may cause warmed tissue to be damaged by the cold that follows.

For damaged plants, be patient. If the tips put out new needles the branch will recover. Any branches that do not have new growth by summer should be cut back to a healthy branch or a main stem.

After two to four years the old damage will be hidden by new growth.

Remember to water well during dry spells in the summer.

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