Itís May and soon flowering trees and shrubs will be ablaze with white and pink blossoms. We tend to think of crabapples (genus Malus) trees in the San Luis Valley (SLV). But ornamentals of the Prunus genius do well here as well.
However, only seven species are allowed to be imported into the SLV. According to the Department of Agriculture, ďThe purpose of this Quarantine is to protect the potato fields in Alamosa, Conejos, Costilla, Rio Grande and Saguache counties against the over wintering host of the primary aphid vector of certain viral diseases that affect potatoes.Ē
Prunus trees and shrubs are collectively known as stone fruits. Allowed in the valley are some cherry and almond species. The ornamentals are closely related to heavy fruit bearing trees but are grown for their spring blossoms, attractive shape, and foliage color. And some provide a bonus of edible fruit.
Probably best known is our native Chokecherry (Prunus virginiana)  shrub used for jelly and wine. A tree variety, Canada Red Chokecherry (Prunus virginiana ĎShubertí) is one of my favorites. I have two in my yard. Early in the season, white blossoms and bright green leaves adorn the tree. Soon after, the leaves turn a beautiful maroon. Iíve never collected any of the small fruit Ė the birds get to it first.
Amur Chokecherry (Prunus maackii)  is closely related, but Iíve not been as successful with it. My specimen usually leafs out fairly early and then drops its leaves after even a slight frost. Itís grown very little in the five years Iíve had it.
I have two species of flowering almonds. One is just starting to bloom this week. It has single pink blossoms and I think it is Prunus glandulosa , but it might be Prunus tenella. I purchased it before the import ban. My favorite bloomer is the flowering almond, Prunus triloba , which is also called Rose Tea of China. It displays gorgeous double pink blossoms if we donít have an untimely, hard freeze. Growing eight to ten feet high it does well in protected areas of my xeric garden.
It took me several years to find out what it was! One spring, when they were in full bloom, I was bold enough to ask five home owners what type of shrub it was. None of them knew! About 10 years ago, I spied one in bloom at a nursery and snapped it right up.
Two other shrubs I have are Western Sand Cherry (Prunus besseyi)  and Nanking Cherry (Prunus tomentosa) . Theyíre in unprotected, xeric parts of my garden and do come back each year but arenít thriving. My Nanking Cherry is about two feet high. Iíve seen them as tall as 8 feet in other gardens in wetter, more protected areas. Iíve only had a few cherries from the Western Sand Cherry and none from the Nanking.
Iím not familiar with the Purple Leaf Sand Cherry (Prunus cistena) . Apparently, it is similar to the Western Sand Cherry, but has purple leaves. Does anyone know of any in the valley? Iíd love to see one. Email me: Marilyn@AlamosaTrees.net.
Besides Prunus species, other than those listed about, I know of only two other trees in Alamosa that are on the Colorado Noxious Weed List. They are Russian Olive (Elaeagnus angustifolia) and Salt Cedar or Tamarisk (Tamarix chinensis, Tamarix parviflors, and Tamarix ramosissima). Unfortunately, Russian Olives, which do very well here, out compete native streamside vegetation and is no long allowed to be sold in Colorado. Itís a prolific seeder. Birds eat the seeds, donít fully digest them, and deposit them all over the place. They grow quickly in bosque environments.
Salt Cedar, with its fernlike branches and fall pink color is very lovely, but invasive in moist habitats with saline soils in the Southwestern United States. It propagates easily through dispersal of its tiny, tufted seeds that dance on the wind and through its spreading roots. Low branches covered with soil will also produce roots. For more information visit AlamosaTrees.com.
ďFor my generation of conservationists, I believe we must change our thinking. I believe that in cities is the preservation of the world.Ē
Senior Scientist, Nature Conservancy