Autumn In the Pacific Northwest

Foggy mists have finally returned autumn to us who live along the coast of western Washington State. Summer was striking in the intensity of drought combining with intermittent heat events. The most exposed edges of the landscape holding trees without a watering schedule were observed to be filled with discolored leaves turning crispy first on the outermost and highest limbs. Western red cedars are the most visible indicators of current stressors affecting trees with many holding a concerning percentage of browning needles. Most red alders and even transplanted redwoods without shade on their roots were seen to have visible symptoms of distress.

We have come to a point of change where shading of root crowns and lessening the amount of evaporation of moisture from the soil surface have become tantamount to the survival of both native forest- and planted ornamental trees along edges and within property and landscape. A watering schedule cannot be recommended for many of these plants as water tables are dropping, some already becoming brackish in nature when nearer the ocean. Proactively adding “xeriscaping” or dry-lands landscaping design elements will help create sustainable plant growth along edges most exposed to meteorological extremes. Along these lines, deciding whether hardwood or coniferous mulch would be better to apply to the soil surface around plants can be leapfrogged by using rocks as mulch. Closely spaced rocks do well to shade the soil surface from UV penetration, keeping roots cool and any soil moisture accessible for longer. Rock mulch also helps to moderate the local temperatures as it tries to penetrate the soil, holding the heat of the day into the night and keeping frosts away. Rock mulch does not need to be reapplied, just weeded occasionally. Thankfully this process is made much easier as any weedy growth tends to be spindly and easy to pull as it grows through the rocks. It is important to make sure the rocks being used do not hold accessible, toxic amounts of minerals or elements. Rocks can help nutrients in the soil from being washed away so quickly by precipitation events, but some additional nutrients (compost tea is a good one) will need to be applied occasionally as the input of organic debris decreases using rocks as an artificial, top layer of the soil’s surface. Organic mulches of all types may be applied as well to benefit plants but must measure under 4 inches in depth and be matched with the plants involved or limiting growth environments may be inadvertently created. Acidic mulches should be used with plants desiring the same. A half- to one-inch-thick layer of seed-free, aged manure can be applied around ornamental maples yearly to sustain healthy growth.

Along with applying needed mulch, now can also be the time to clean up diseased leaves and needles around your trees. Some examples of the most visible, prevalent pathogens are the pinkish needles sometimes found on weeping blue atlas cedars and alpine firs, as well as leaves on fruit trees which exhibit red or orange spots that eventually become holes. Remember, any diseased vegetative matter should be burned or thrown into a landfill, NOT put into compost or green waste bins.

Additionally, have you been through a hard sell on tree work, where someone came up to your door sharing concerns about your trees and recommending tree removal, spraying for beetles, or “wind-sailing” to reduce drag on the tree? If this has happened to either you or your friends, I am collecting stories and would love to hear about your experience. My email address is: salpstc@gmail.com. Please feel free to ask me tree questions or share your concerns.

Yours-in-Trees,

Sal

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