In early May I noticed some caterpillars in a Douglas Fir I was pruning away from a roof in Seattle. A little investigating online and in a few of my resource books confirmed that they were silver spotted tiger moth caterpillars. Douglas fir (Pseudotsuga menziesii) is the principal host, but they also feed on a few other conifer species. One of the keys in identification of this species is the large size of the caterpillars at this time of the year (mid April to early May). Nearly all other species don’t reach this size until later in the summer, so seeing a caterpillar of this size narrows down the options tremendously.
Their eggs hatch in the late summer or fall, and they will feed on needles during warmer winter days. By June, Lophocampa argentata start spinning cocoons near their host tree. Adults start flying in July and August, laying eggs to start the life-cycle again.
Thankfully natural predators such as parasitoid wasps and songbirds nearly always keep this defoliator in check and don’t allow it to cause long-term damage. If their presence becomes intolerable, the individual branches with the webbing can be pruned out and destroyed.
Lophocampa argentata on a Douglas Fir branch
Notice the caterpillar frass caught in their “tent”
I wanted to share a couple photos of a cherry I pruned last week. I started a multi-year process to create more healthy fruiting branches lower in the canopy where fruit can be reached. This first pruning in many years started by removing some of the highest more vertically-oriented branches in the upper canopy to create more light and airflow lower in the canopy. Thick areas were also thinned so the branches can dry out sooner after rains, which will help reduce fungal infections. Many people say a sign of good pruning is that it’s not entirely obvious that pruning has occurred. If I may so myself, I think this is a good example. There’s an obvious difference between the before and after, but if one just saw the post pruning photo, it’s not obvious it’s been pruned.
Lots of thick areas in the canopy, and several vertical shoots going nowhere but up.
After thinning some of the thickest areas and reducing the height appropriately.
When planting trees it’s important to remove all the soil that it comes with. Besides making sure you’re planting it at the correct depth (very important!) which is very hard to tell without removing the soil, you’re helping the tree get accustomed to its new home quicker. Often the soil it is grown in at the nursery is heavily amended to make the trees grow quicker. If this is left on the root ball of the tree when you plant it, and your soil is not as appealing to the tree, its roots may just hang out in this little zone for years without much exploratory growth outwards to create a strong and stable root system. It’s also important to look for and remove any girdling or circling roots and trim off broken or damaged ends. Poor planting often doesn’t show up for years, and may not become a problem until there’s a particularly strong windstorm, or a very dry summer, and those circling roots can’t hold the tree up or find sufficient water.
I removed a number of dead Arborvitae shrubs last month in North Seattle that died in the summer 2017 drought. It was very obvious that the only preparation to the tree was the burlap taken off their roots, and they were then just dropped into a hole. You can see the slick edge of the root ball from one of the dead arborvitae in the photo below, hardly any roots grew out of this packed soil into the native soil it was planted it.
The slick edge of the rootball is still visible 3 years after transplanting. New roots had trouble growing through this into the native soil, eventually leading to its demise, as it couldn’t get enough water during a drought.
Carefully washed roots from a Japanese maple, ready to be planted
It may sound like some kind of monster, and in some ways it is, though normally it just appears as in innocuous fungus at the base of hardwood trees. It’s a fungus called Kretzschmaria deusta found in temperate climates worldwide that can cause fairly severe decay. It has two visual forms. In the spring it grows new fruiting bodies that are gray with white edges that emerge directly at the base of trees and logs that are infected. Later in the year these turn into black crusty lumps that look like charcoal blisters. Both forms can be seen on a Big Leaf Maple in the photos below that I took during the spring in South Seattle.
Both forms can be seen in this photo. The new gray and white growths, and prior years black coal looking lumps.
The fungus is a decayer of both cellulose (the fibers that add flexibility) and lignin (which give rigidity to wood). Thus it can be a fairly damaging fungus.
A glove for size comparison. K. deusta can be damaging to trees, usually indicating some significant decay. Any sightings should noted and investigated further.
Another reason not to prune a lot out of a tree all at once- I was working in Seattle in the upper canopy of a narrow leafed Ash (Fraxinus angustifolia) last week, and noticed the top of a number of the major limbs were no longer alive. It appeared that a huge amount of foliage had been removed by the power company a couple of years prior, exposing once shaded limbs to full sun all day long. The tops of these limbs got sunburned and died. They are now more susceptible to insect pests and diseases, potentially weakening the tree. The lesson: prune in moderation whenever possible!
As a general rule no more than 25% to 30% of the total leaf area (when leafed out) should be removed during any one year period.
Sunscald on an Ash branch from sudden exposure to day-long sun.
I came across something interesting last week while removing a small cypress tree in the Madison Valley of Seattle. The tree had a lot of recent branch and foliage die-back and generally was not looking robust.
When I made the final cut low on the trunk I noticed a fair amount of decay (notice the spongy looking parts of the trunk in the photo on the left). What I found interesting were the narrow bands of white fungal mycelium that were visible in the bark. They seemed to be only in the areas directly adjacent to the sections of rot further in the trunk. Perhaps the fungus decaying the wood is also visible in the otherwise healthy looking outer bark?
I think a very close look at the bark layers (without removing the tree or even damaging the trunk) would have indicated the internal decay. Something I made a note of in case I come across a similar looking cypress tree in the future.
To know if the two observations are actually correlated one would have to identify the fungal species, likely quite difficult since it wasn’t fruiting.
This tree had limited areas of healthy xylem and cambium, some of which can be seen in the upper left side of the trunk.
Note the bands of mycelium in the outer layers of bark.
Adding wood chip mulch around young trees is one of the best things one can do to assure their success. As I’ve mentioned in previous posts, wood chips have a number of benefits. From moderating soil temperature, holding moisture through our dry summers, preventing erosion, to inhibiting weed growth, and eventually decomposing to help build healthy soil.
Another function they can serve is to prevent damage to surface roots. The birch tree pictured below looks like it was a victim of an unknowing “mow and blow” landscaping crew. These are the landscape crews that keep a lot of yards looking clean and tidy with straight edges and rounded bushes. One of the main tools in their arsenal is the leaf blower. Besides the noise and air pollution, there’s another reason the use of these machines should be limited in the landscape- soil erosion. Leaf blowers can create wind speeds from 140 to 270 mph (according to Wikipedia), easily strong enough to blow loose soil particles away. I’ve watched numerous landscape crews around Seattle remove weeds (either by hand or with tools) then come through to blow away leaves and other debris with a leaf blower. As the leaves are getting blown away, loosened soil particles are as well.
Exposed and damaged roots.
Anyway, back to my photo of the birch tree: repeated soil disturbance and leaf blower usage around the base of this tree has likely lowered the soil level, allowing the roots to be exposed and then damaged by other lawn care equipment. These are likely the structural roots of the tree, the roots that the tree needs for the rest of its life to physically hold it in place. Placing mulch (preferably woodchips, not bark) around the base of trees, but not against the trunk, prevents a lot of potential problems, and benefits the tree in innumerable ways.
So get out there and mulch in preparation for our dry summer!
The exposed roots covered with a protective layer of wood chip mulch.
It’s flowering time for the plums here in the Seattle area, specifically the Asian type of plum (the European types bloom later). Pruning on these trees can also begin in the next couple of weeks. There are less fungal spores in the air that might infect pruning cuts, and the trees are out of dormancy and able to respond to these small wounds. Shortening some of those really long horizontal branches that can sometimes break at the end of the summer when they’re laden with fruit, might be a good idea. Also, thinning thick areas of the canopy to increase airflow and sunlight helps increase fruit quality. If you’re not feeling confident in your pruning skills, give me a call to schedule a lesson.
Larches are a type of conifer that lose their leaves (needles) for the winter. This sometimes causes people not aware of what they are to think they are dying, despite this being a completely normal process.
Larix species are native to portions of Washington state, among other places. There are a number of species and varieties, including this small weeping one I recently pruned.
This weeping larch hadn’t been pruned (besides “skirting” the bottom) for at least 5 years. Lots of deadwood make the structure hard to see even during the winter after it has dropped its needles.
After removing the deadwood, and selectively thinning some of the live branches in the thicker areas.
Autumn Olive. An interesting and useful plant for your landscape. It produces small red or orange berries late in the summer that are a great snack right off the bush. They’re high in a number of the same beneficial nutrients found in tomatoes, but in much higher concentrations. Elaeagnus umbellata also fixed nitrogen into the soil, so it can help rebuild soils or be planted near trees that will eventually outgrow it, adding nitrogen to the root zone of the long lived tree. Autumn Olive grows up to about 12 feet tall in most sites. Another very similar fruit is Goumi (Elaeagnus multiflora). There is a fair amount of confusion between the two, especially online.
I took this photo of Autumn Olive in bloom at the end of march in the Skagit Valley.
Caution is advised, as some say both species can become invasive via bird spread seeds. Although I haven’t seen this occur in my experience, nor have I heard this from fellow gardeners in the Pacific Northwest.