150 Mature Park Trees – What’s the Future? Part 1

By Marilyn Loser

Did you know Alamosa Parks contain 322 trees? I know; I counted them. I’d consider almost half to be mature since they have diameters of at least two feet. The 78 largest trees, with diameters of three feet or more, are in our two oldest parks: Cole and Boyd. Three species make up the mix of these grand oldsters: cottonwood, Siberian elm, and willow. We rejoice in our trees and, of course, Alamosa was named for its cottonwoods.  In 1878, many of the first buildings were brought in by rail and “planted” on the ground. The trees in the bosque were mostly cottonwoods and the surrounding landscape was largely treeless.

I believe the oldest trees in Cole Park were planted in 1937/1938 (see September 2 column). All three species of our older trees have relatively short life spans.  The plains cottonwood is the Wyoming state tree. The Cheyenne Tree website states that  cottonwoods “on average have a safe lifespan of 70 years.” Perhaps all of our trees are “above average” (even if we don’t live in Lake Wobegon) and will safely live more than 100 years.  I don’t think this scenario is likely.  We need to begin planting new trees so when the grand oldsters need to be removed, our parks won’t seem desolate. 

I’m not advocating that we rip out all the old trees. However, we need to be mindful of safety and of the future.  Alamosa is not alone in dealing with old cottonwoods. Nevada’s new state park, the Dangberg Home Ranch in Carson Valley, needs to replace the enormous cottonwoods, which have shaded the heritage ranch for 100 years, to protect the home and public from falling limbs. They don’t want to replace them all at once so are having to provide damage control (removing dangerous limbs) while new trees begin to mature.

So what species should we plant? The problem with replanting using only the current dominate species of short-lived and weak-branched trees is that we’ll be in our current situation in another 70 years.  Cities such as Seattle don’t even allow cottonwoods to be planted due both to their brittle wood that breaks in the wind and their aggressive roots. Not much of a problem in a bosque, but how about a well-attended public park?

Given our unique climate, we don’t have as large a tree palette as many other cities.  However, there are a number of species that would probably do well here that are longer-lived due to harder wood and stronger branching.  Some are medium sized and would require less water and maintenance while still providing a beautiful, shady canopy.

In a perfect world I would select a tree on beauty alone, but there are other considerations. I think we should add some hardwood tree species to our park palette. They would have a good chance of dazzling Alamosans for at least 100 years.     I know trees mature more slowly here than in milder and wetter climates, so let’s get started now.

Carol Lyons, executive director of the Institute for Environmental Solutions in Denver, studies how trees affect Colorado’s urban environments.  Although Alamosa is more rural, there is much to be learned from such urban studies.

Lyons considers four categories in relation to tree species: air quality, carbon storage and sequestration, energy conservation, and water conservation.  She lists three species that excel in all three categories and grow in Colorado: the Kentucky coffee tree, green ash, and bristlecone pine. 

Does anyone know of a Kentucky coffee tree growing in the San Luis Valley? If so, please let me know! Email me at marilyn@alamosatrees.net or call 719.589.3295. Native to the eastern US and once the state tree of Kentucky, its beans were used as a coffee substitute.  It is well-suited to climate zones 3 and 4 and is considered a hardwood tree, but I’m not sure about its elevation range.  One source gives an upper limit of 7,500 ft (Alamosa is 7,543 ft); most sources don’t give elevation limits. The bean pods can create a litter problem.

We have 16 ash trees in our parks; I believe most are green ash and none have diameters greater than 14 inches.  Not a hardwood tree, it does well in Alamosa and there are many on private property. Often they turn brilliant yellow in the fall and drop their leaves while cottonwoods are just beginning to turn. The winds of the past week have left most ashes in town bare.

Bristlecone pines rank among the longest-lived trees in the world.  They are small and grow very slowly.  I do not recommend them as a park tree.

The next column will continue this discussion. For more information, go to http://www.alamosatrees.net and peruse the tree lists.

“He who plants a Tree loves others besides himself.”  Thomas Fuller