Up and down my street Colorado blue spruces are dying from the bottom up. At first, I thought that the branch deaths were just normal self-pruning, but now I am afraid that it is more serious than that. Blue spruces are native trees of the arid, short-summer zones of the Rocky Mountains. Planting these trees in the moist soils of Pennsylvania and exposing them to our long, humid summers (summers that are getting longer and more humid with each passing decade) stresses the trees and sets them up for invasions by a wide variety of fungi and arthropod pests.
Most of the spruces on my street have lasted fifty or sixty years, but they are starting to fade. Typically, a tree sheds its older (lower) needles first and hangs on to the upper, younger, more efficiently photosynthesizing needles for as long as possible. Sometimes the trees keep an outer shell of living needles while the central core turns brown and dies, and sometimes entire branches turn brown and wither. Each of these patterns fit specific fungal diseases: the fungi are opportunistically invading the trees because the tree’s energy is diverted elsewhere fighting the environmental stresses that are challenging their homeostasis. These spruces are a long way from home, and everything is changing rapidly all around them. Urban foresters at Michigan State University indicate that an increasing number of formerly harmless fungal species are now causing needle and branch loss and death in blue spruces that are planted outside of their native zones.
Spruces are trees of genus Picea. You can recognize a spruce tree by its whorled branches (branches that radiate out like spokes of a wheel from a single level on the trunk) and by its singularly arising needles that spiral around on its branches. These needles are anchored to their branches by peg-like structures that remain on the branch even after the needle is shed. This makes the branches of a spruce rough to the touch.
I am sitting on my deck looking at a huge Norway spruce (Picea abies) and its bordering set of still healthy but not quite as large Colorado blue spruces (Picea pungens). These trees were planted seventy years ago on the west side of my house in the fresh, rocky spoil from the foundation’s excavation. They grew into a fine wind break and a great afternoon shade wall. They were planted not quite far enough apart, though, to prevent competitive shading and branch pruning. They had grown into a continuous mass of trees with intertwined branches and a dense, ground mulch of shed needles. The walls of drooping, skirting branches enclosed the “forts” in which my children played. Every once and a while acorns dropped by passing crows or blue jays germinated in these fort rooms, too, and their seedlings slowly grew in the deep shade.
Nine years ago a wind storm took out two-thirds of my blue spruces. Maybe the insidious effects of stress and infection had weakened them and made them vulnerable to wind breakage. The “fort” of spruce rooms was broken up, and the now sun-drenched oak saplings grew up into the opened spaces. The single Norway spruce and a handful of unconnected Colorado blues remain. The Norway spruce leans disturbingly toward the house, and the blues have strange shapes from their competitive shading interactions with their now departed neighbors, but these trees, thank goodness, still seem sound and healthy.
In any list of common trees of Pennsylvania these two, alien spruces, Colorado blue and Norway, show up prominently. Drive any neighborhood, hike any trail, walk through any city park and there they are! All of these spruces were intentionally carried by humans to their spots and planted. Ninety-five percent of all of Pennsylvania’s primal forests have been cut down, and these adopted spruces are two of the common replacements. “Colorado’s” from the Rocky Mountains are growing throughout the Alleghenies, and “Norway’s” from the western Urals down to the Carpathians are covering Laurel Hill and Chestnut Ridge.
There is a town named Spruce just north and east of here. There is a Blue Spruce Park nearby, too. There is a Spruce Hill near Juniata and a great trout stream called Spruce Creek (notably fished by past presidents and famous football players). There are Spruce Streets in Philadelphia and Pittsburgh (and in many towns in between). There are law offices, schools, bakeries and churches with “spruce” in their names. There is even a Spruce Lake over in the Poconos. My guess is that all of these were named either for the alien spruce trees planted here by people, or for the memory of some faraway spruces, or by mistake due to a failure to identify and name trees that actually were not spruces.
There are only two native spruces in Pennsylvania: bog spruce (Picea mariana) and red spruce (P. rubens). The bog spruce grows in sphagnum bogs and the red spruce grows around the edges of those same bogs. Sphagnum bogs are not common parts of our landscape, and they are not places one usually finds people or streets let alone a bakery or a church. These native spruces are seldom seen: they never make the lists of the ten (or twenty or even thirty) most common trees in the state. They won’t grow on command in nice straight lines alongside streets or next to houses. They won’t survive if they are surrounded by concrete or if they are planted in loose, rocky fill. They need to have their roots kept very wet, and in the spring and summer they are often covered with black flies and mosquitoes. Most people keep their distance.
The eastern hemlock (Tsunga canadensis) is the state tree of Pennsylvania. It grew in dense stands in the primal Pennsylvania forest and covered vast areas of the state. It was, though, much to its ecological distress, a tree of great utility. Its coarse wood was used first to build cabins and then as mine props and railroad ties. Its bark was a rich source of tannins and other useful chemicals needed by the early industries in the state.
As important as the hemlock was, though, it was often called something else! Mason and Dixon (the famous line makers) called hemlocks “spruces.” It is not recorded what they called pine trees or if they ever saw one of our true spruce species. Many of our more distantly named Spruce towns and streams might be due to this surprising and terribly common (and maybe contagious) error.
I had to cut down one of my blue spruces this summer. It quite suddenly dropped all of its remaining needles and stood dead and increasingly brittle right next to the electric lines running into both my house and my neighbor’s. This tree had a very odd shape. It had lost limbs and apical branches in storms and had a twisted, cartoon-ish shape. We called it “Uggo the Tree.” The birds waiting for their turns at my front yard feeders often lined up on Uggo’s limbs, and one cold, fall night coming home late from teaching I saw a great horned owl sitting on Uggo’s upper branches waiting for a rabbit or skunk to come into the feeder area for a snack. Goshawks and sharp-shins used Uggo for their hunting perches, too. Uggo, though, succumbed to the fungi around him and had to be taken down before he fell down. Uggo will be missed by by birds and humans alike!