By now you should have your garden maintenance under control. Weeding is done and any early plantings hopefully are established enough to make it through the heat of the summer. So let's look ahead to fall, a good time to plant trees.
Trees shade and cool our house and yards, bring birds in close by, and mark the changing seasons. I don't know about you but I loved to climb trees as a child, or until I became afraid of heights.
There are different categories of trees for different purposes, with some being found in more than one category. There are the stately shade trees, flowering trees, fruiting or nut bearing trees, trees whose leaves turn color in the fall, and of course, the evergreen trees that can be single specimens providing yearlong screening from neighbors or other distractions.
But today I am going to briefly cover what I think are some of the best shade trees for our area. First, when considering where to plant, make sure your planting site selection does not encroach on your neighbor's space, interfere with overhead wires, shade gardens that need open sunlight, crowd your house or crowd other trees. And make sure it does not interfere with underground pipes, utilities or even walkways. Of course these "don'ts" require you to know the mature height and width of your selected trees.
So what are some of my favorite trees? The maples are great and can provide good fall color. The Pacific or Norwegian Sunset maples (35 high and 25' wide at maturity) and the Norway maple (45'H x 40'W) are trees that do well here and don't appear to have a problem with our alkaline soils and subsequent chlorotic leaves. The sensation boxelder (50'H x 40'W) is another maple that does well here. I recommend against planting Silver maples.
Oaks are under-planted in the Surface Creek valley. I would include the Bur oak (50'H x 40'W), the white Oak (50'H x 35'W) and the English Oak (40'H x 40'W). Good fall color is one of their attributes.
Now I know I'll get raised eyebrows when I recommend a few elm trees. But unlike our ubiquitous Siberian elms which produce jillions of seed with the resulting nuisance weed seedlings and elm seed bugs, my selections have none of those undesirable characteristics. My choices include the Frontier elm (40'H x 35'W), Chinese elm (Lacebark) (50'H x 45'W), and the American elm (70'H x 45W). Their leaves have mostly yellow fall color.
Other trees I recommend include the Kentucky coffeetree (45'H x 35'W), Littleleaf and American lindens (60'H x 35'W), Shademaster (50'H x 45W) and Skyline (50'H x 25'W) thornless honeylocust trees. These are all great trees with mainly yellow fall color. The honeylocust trees provide filtered shade and are also podless.
Trees I do not recommend planting include most cottonwood natives and cultivars because of their susceptibility to wind damage; Russian olives, which are classified as noxious weeds in Colorado; and globe willows, because of their constant shedding of branches (called "self-pruning") and susceptibility to wind and early snowstorm damage. These willow trees are also host to many pests and diseases. I've already mentioned the Siberian elm. Don't let any of those pioneering seedlings get a toehold and become a large landscape pest.
I've got to mention the ash trees because they used to be great trees to plant and included the green and autumn purple ashes. But the spread of the devastating emerald ash borer means that this pest will eventually infest our area. This pest is already on Colorado's Front Range in Boulder County, and every last unprotected ash tree will be killed by these pests. While a single yearly insecticide treatment will protect an ash tree, I certainly would not plant any more than one or two of these trees and only if I am willing to treat for this pest every year, forever.
So that's my list. It is certainly not all inclusive so don't be offended if I didn't mention your favorite tree.
Jim Leser retired to Cedaredge after a career with Texas A&M University Extension in entomology. He is a member of the Cedaredge Tree Board and a Colorado Master Gardener.