• List of Trees and Shrubs for Cheyenne
  
  
• Watering Trees
  
  
• Pruning Trees
  
  
• Planting Trees
  
  
• Licensed Arborists
  
  
• Cottonwood Trees
  
  
• Street and Park Tree Evaluation for Cheyenne
  
  
• Conifer Trees Planted Along the Street
  
  
• Tree Information in General
  
  
• Historic Weather Information: Averages, Max. and Min., including Wyoming's Wind
  
  
• Publications
  
  

Questions? E-Mail Forestry Division
If possible, take a couple of digital photos of your tree or shrub and include them with your questions. One photo should be a close up of the problem area. The second photo should be of the entire tree if possible.

Watering Information For Trees

We are in our entering our eleventh year of drought. We are noticing trees throughout the city that are showing drought stress. Evergreens -- pines, spruce, fir, and junipers are the most at risk from a dry winter. Many large trees in Cheyenne primarily cottonwood, Siberian elm, and ash have significant die-back. Soil moisture is depleted causing the larger trees to show the affects of the drought.

• Watering details for trees in Cheyenne
  
  There is a wealth of information concerning watering trees, low water using landscapes, and water saving ideas available at these Websites:

• Denver Water Department - Save Our Shade
• Green Industries of Colorado
• Xeriscape for Wise Water Use
• Water Wiser Program

Tree Information in General

The Environment and Culture of Cheyenne's Trees

• Historic Weather Information: Averages, Max. and Min. including Wyoming's Wind

Historically the climate in and around Cheyenne is defined by:

1. 15.45 inches - Average yearly precipitation.
2. Zone 4b to 5a - USDA Plant Hardiness Zone low temperatures usually not below -20 degrees F.
3. Infrequent record low temperatures of -30°F occurring in December, January, and February since 1940.
4. Occasional, moderate to high summer temperatures, low to mid 90's.
5. May 18 - Average Date of last Spring temperature at or below 32 degrees F.
6. September 25 - Average date of first Fall temperature at or below 32 degrees F.
7. Sustained, dry, winds.

Supporting vegetatively, a short grass prairie, with native trees such as cottonwoods, willows, and boxelders around areas of frequent or persistent water retention.

Typically trees will not grow in this area without initial human support through watering, fertilizing, wind protection, and insect and disease control. Trees that are suited for USDA Hardiness Zone 5 and above are at risk of dying during periods of record cold. Trees suited for zone 4 and below are relatively safe bets for this climate.

Without initial human support, trees under stress are easy targets for insect and disease attack.

Late spring freezes can cause significant depletion of food reserves in the tree by killing emerging new growth, forcing the tree to "push out" additional new growth. Average last spring frost day May 18th.

Hail occurs frequently during the spring and summer months in Cheyenne. Hail damages limbs and trunks. Trees use energy reserves to compartmentalize hail damage. Hail damage causes open wounds, easy access for insect attack, and disease infection.

Early autumn moderate snowfall or freezing rain can break limbs or entire trees due to snow and ice accumulation on the tree leaves. Major limb breakage opens the tree to insect attack and decay fungus infection.

Shallow rooted trees are weakened or killed by yearly or cyclic periods of drought conditions.

Evergreen trees are susceptible to death by dry and windy winters due to evapotranspiration that occurs year round. Mechanical rubbing injury to limbs, twigs, and needles is caused by wind.

Cheyenne's high elevation (~6,100 feet) means more intense sunlight, especially in winter when the sun is low in the south and snow is on the ground. Direct and reflective heating of the south and southwest side of tree trunks results in higher chances of sunscald damage to young thin-barked trees. Trunk damage from winter sun heating is also known as southwest disease and sunscald.

Tree species selection in Cheyenne is limited due to these conditions. Many of the broadleaf deciduous trees that are growing well in Cheyenne are not very strong trees. The cottonwoods, poplars, willows, Siberian elms, and soft maples like boxelder and silver maple, are fast growing short-lived trees. Fast growing trees usually equates to structurally weak trees. Cottonwoods, poplars, silver maples, and willows can grow very large limbs in a short period of time, 20 years. These fast growing trees are more likely to acquire a wood decay fungus in the interior heartwood of the trees. Frequently these trees will have large hollow limbs or trunks initially caused by wood decay fungus. Squirrels and cavity nesting birds take advantage of the decaying wood by excavating it out of the tree to make a home for themselves. Although structurally weakened, trees with hollow cavities in limbs and trunks are critical habitat for birds and squirrels. The challenge is to provide habitat for urban wildlife and to keep trees safe for human activities below them.

The Siberian elm, commonly, but incorrectly known as a Chinese elm, is an imported tree from Asia, initially used to a great extent in wind breaks throughout the Great Plains states. This tree species can grow just about anywhere and under any condition. The life expectancy of Siberian elms is usually 40 to 60 years. They produce an abundant amount of seed that will sprout anywhere including lawns, alleys, and in cracks in street pavement. Most Siberian elms will still have green leaves at the end of October. An exotic insect from Asia, the banded elm bark beetle, is causing mortality in the Siberian elms in and around Cheyenne. Trees retaining leaves into the snowy months are more likely to suffer major limb breakage when snow collects on the leaves and limbs. Since they are in green leaf late into the season not only are they susceptible to snow damage, they are susceptible to extreme temperature drops as well. The Halloween freeze in 1991, when the temperature dropped from the 60's to below zero in a short period of time, killed or caused extensive die-back in many Siberian elms in the northern Great Plains.

Cottonwood Trees: Facts and Info

Wyoming State Tree:  Plains Cottonwood, Populus sargentii Dode.

Size:  60 to 100 feet tall,  60-100 foot canopy spread,  trunk diameter up to 5 or 6 feet.

Minimum Ground Space:  15 feet diameter of open ground around a cottonwood tree trunk.

Lifespan:  Variable, up to 100 years.

Female cottonwood trees:  Produce the cottony covered seed.

Male cottonwood trees:  Produce pollen.

Wyoming State Tree - Plains Cottonwood, Populus sargentii Dode. Dendrologists do not have a consensus of opinion if the Plains cottonwood is a separate species or a variety of eastern cottonwood - Populus deltoids var. occidentalis. Cottonwood trees are in the Willow family and the Poplar genus.

The plains cottonwoods, eastern cottonwoods and other true species of cottonwoods are majestic and magnificent trees, especially when they are allowed to reach their full, unrestricted growth potential. Cottonwoods grow well in Cheyenne and in Wyoming in general. Cottonwoods are typically found growing along streams, irrigation ditches, and around lakes. Although they grow best around a source of water, they can tolerate dry soils, if grown in dry soils from the start. Cottonwood trees grow fast, can grow large heavy limbs, are weak-wooded, are prone to wood decay, and on average have a safe lifespan of 70 years. Additional information on cottonwoods at National Arbor Day Foundation.

Cottonwood trees are dioecious, which means they have male and female flowers on separate trees. The pollen in male flowers is ripe in late March and into April. Wind borne tree pollen, including cottonwood pollen is a major source of allergy problems for many people.  Cottonless cottonwoods are clones of male trees, which have pollen. The fruit of the cottonwood borne on the female tree is in the form of a seed surrounded by a cottony substance, hence the name of the tree -- cottonwood. Like the pollen, the seed is distributed by the wind. The seed capsules open in late May through June. Although the cottony-seeds can be a nuisance, they have NO allergenic properties. People with allergy problems during the time of the cottony-seed distribution are probably suffering from other wind-borne pollen from grasses, weeds or late pollinating trees. There are no Cheyenne city laws, nor any state statutes prohibiting the planting of the female, cottony-seed bearing tree. Tree nurseries typically do not sell the female, cottony seed bearing, trees.

Plains cottonwoods in Cheyenne can develop a trunk five feet in diameter (an example is on the 1200 block of West Pershing). On average, the mature and over-mature cottonwoods in Cheyenne have two and a half to three foot trunk diameters. The upheaval of the soil around the base of the tree caused by the root flair can be an additional three feet around the trunk. Five feet of tree trunk with three feet of root flair on all sides of the trunk can require an 11 to 15-foot diameter circle of ground surface for unhindered tree trunk and root flair development. The tree lawn area in the public right-of-way, the landscape area between the street and sidewalk, should be at least 12 feet wide to allow a cottonwood to develop to its full trunk and root flair potential without damaging other infrastructure such as the sidewalk and street. A cottonwood planted in a narrow or small ground site will push up the sidewalk and curb near the tree, which requires repair of the damage. Replacing curbs, gutters and sidewalks requires cutting tree roots. Often, large roots will have to be cut. Trees with cut roots result in structural stability problems for the tree and diminished water and nutrient uptake by the tree, which can cause a decline in tree health. A decline in tree health can result in increased insect and disease attack, limb die-back, or complete tree mortality. Damaged sidewalks can exclude wheelchair use and restrict pedestrian use. A good example of damage to sidewalks, curbs, and gutters caused by cottonwood trees planted in a narrow space, is around the city block bordered by West Pershing, Cribbon, West 32nd, and Dey. More info on Large Shade Trees.

3200 Block of Dey Avenue showing a narrow Tree Lawn between the street and sidewalk. Top photo shows a ground view of sidewalk blocks heaved by a large tree root zone. Bottom photo shows the narrow Tree Lawn with sidewalk damage evident.

Plains cottonwoods can develop a leaf canopy of 40 to 100 feet in diameter. Ideally, shade trees that can reach the size of a cottonwood should be planted so that there is minimal leaf crown interference with each other. A spacing of at least 40 feet between large shade trees is desirable.

All of us, as current stewards of the city, have a responsibility to future generations to utilize our current research, information, and technology to provide a functional, sturdy, long-lasting infrastructure, which includes trees.

Cheyenne City Code requires that vegetation including trees located in the public right-of-way abutting private property is the maintenance and cost responsibility of the property owner.

Cottonwood trees, like historic buildings, require maintenance. Tree maintenance includes: watering, occasional fertilizing, treating insects and diseases, and pruning of dead, broken, weak or diseased limbs. Maintenance can be expensive, especially pruning. Federal funding through Community Development Block Grants (CDBG) administered by Cheyenne Housing and Community Development at 307-637-6255, is available for low income families for removal of trees only. Currently, there is no financial assistance available for property owners to prune their trees. Pruning weak, broken, and dead limbs off of a tree can extend the safe lifespan of trees including cottonwoods.

Responsible street tree planning requires species diversity.  A tree inventory/evaluation was done in 2004 in the central part of Cheyenne found that Populus species trees (cottonwood, poplar, aspen) comprise 19.8% of the inventoried tree population.

Many eastern cities in the U.S. had streets lined with American elms in the 1800's and into the early 20th Century. In the mid 1930's a fungus commonly known as Dutch elm disease was inadvertently introduced into the United States from Europe. The fungus carried by a European introduced bark beetle, along with native bark beetles, quickly spread Dutch elm disease throughout the United States. Hundreds of thousands of native large leaf elms were killed by Dutch elm disease. Many cities lost all of the street trees on many city streets that were previously shaded by the elms.

We learned from this introduction of disease and insects that planting a wide diversity of tree species is required to reduce the impact of catastrophic tree loss when a disease like Dutch elm disease occurs again. We learned that the Dutch elm disease could be spread from tree-to-tree not only by insects, but by root grafts from nearby trees. To avoid same species root grafts we try to avoid planting same species of trees near each other, even if they are planted 50 feet apart. Tree roots can grow in a radius from the trunk more than 1½ times the height of the tree. If a tree mortality causing insect or disease is introduced into the United States, which specifically attacks cottonwoods, the city of Cheyenne could lose one fifth of all our street trees. An unknown number of cottonwoods on private property would also be lost.

Cottonwood trees can grow in a wide range of soil types. Cottonwoods, in the same tree family as willows, are a good pioneer type of tree for converting grass prairie land into an urban woodland area. Other slower growing trees that have a longer life can be planted in the shade of cottonwoods and in the soils modified by cottonwoods. Although they do not grow well in the shade of larger trees, cottonwoods can still be replanted. Care needs to be taken to allow mixing tree species to avoid a monoculture, which is a close grouping of the same species. A planting plan for a healthy urban forest is to have a wide diversity of tree species.

A Good Tree Planting Method

Tree Spacing in the Public Right-of-Way

If they survive, trees will adapt to the situation in which they are planted or growing. Most large mature trees that grow in Cheyenne are capable of having a crown spread of 30 to 60 feet. Shade trees, or large trees at maturity, planted less than 30 feet apart on trunk centers, have the following drawbacks:

1. Intertwined tree crowns have rubbing branches causing limb mortality or wounds where insects and diseases can enter the tree causing decline or death. Rubbing branches are structurally weakened and fail more frequently than undamaged branches.
   
   
2. Intertwined tree crowns cause excessive shading in that crown intersection resulting in branch die-back. If one of the trees dies or is removed, a large bare area and a disfigured crown will exist on the remaining tree.
   
   
3. Excessive shading from intertwined crowns can promote fungal disease growth in the tree and on plants below the tree. Grass development is limited in highly shaded areas. In the winter, even when the leaves are not on the trees, intertwined tree crowns have a higher shade factor above the street, reducing solar melting of snow and ice from city streets.
   
   
4. Trees in competition with one another for sunlight will concentrate most growth in reaching up for the sunlight, usually at the cost of growing trunk and limb strength to support the rapid height growth.
   
   
5. Shade trees have large trunks. A row of closely spaced large trunks along the street causes a visual wall, hampering the visibility of oncoming traffic from street intersections.
   
   
6. Trees planted close to one another in an area already lacking sufficient ground surface for water and air infiltration into the root zone, such as trees planted along paved streets, compete with each other for the limited supply of water and minerals. Trees in close competition for limited minerals and water are growing under stress.
   
   
7. Reasonable tree trunk movement, swaying in the wind, actually promotes a stronger root and trunk support system for the tree. Trees planted close together or in groups have grown to depend on other nearby trees to damper the wind. Individual trees growing in a closely planted group of trees have not developed strong root and trunk support since the strength is attained as a group.
   
   
8. Tree root systems can grow more than 1½ times the crown spread of the tree. Trees planted close together can have roots that will graft together, thereby establishing a link between the two trees. Contagious diseases, such as Dutch elm disease, which has killed many closely planted American elms in the past, can easily move from tree-to-tree via root grafts.

Ideally, most shade trees require an area of ground that is at least the same size as the mature crown spread. Ideally, a tree with a 40-foot crown spread would require at least a 40-foot diameter area, or 1250 square feet, for unhindered root development. Ideally, the tree crown should not touch any other tree or object to allow the full potential of crown development

Conifer Trees Planted Along the Street

Conifer trees, (e.g.,pine, spruce, juniper, fir) when planted along the street eventually overgrow the width of the planting strip known as a tree lawn, the area of landscape between the street and sidewalk. Required sidewalk height clearance in Cheyenne is eight feet. The required street height clearance is 14 feet. In addition no branches should protrude into the sidewalk and street area. A conifer is a cone-bearing tree. Typically in Cheyenne it is an evergreen with needle shaped leaves. City ordinance prohibits the planting of conifer trees in the tree lawn area.

The growth form of conifer trees is to retain branches low to the ground. Branches low to the ground can grow out from the trunk in a radius of 5 to 15 feet. For example a large spruce tree with low growing branches can cover an area of ground 20 to 30 in diameter. Most tree lawns in Cheyenne are 6 to 12 feet wide. Pruning a conifer tree to provide the clearance required for street and sidewalks can cause the conifer tree to be unsightly, unhealthy, and in some cases predisposing the tree for failure due to wind. Conifers planted on the south side of streets can shade the street surface in winter causing icy conditions on the street. Conifers planted on the north side of street can cause snow drifts into the street. Conifers obstruct the vision of drivers. Pedestrians, especially children, cannot be seen by drivers when they are entering the street from behind a conifer.

Although the small conifer is small when purchased and planted, and for a period of time fits well in the tree lawn, the future brings nothing but problems for conifers growing in tree lawns.

Cheyenne Street and Park Tree Inventory / Evaluation - 2004

The Cheyenne Urban Forestry Division contracted with Davey Resource Group, which is a division of The Davey Tree Expert Company, to evaluate street trees in the older part of Cheyenne and to evaluate trees in Airport Golf Course and in Lions, and Holliday Parks. The cost of the tree evaluation was $40,000. Wyoming State Forestry Division awarded the city a $35,000 grant for the inventory / evaluation and the Cheyenne Urban Forestry Division paid $5,000. The evaluation process began in August 2004 and ended in October 2004. We received the data and Management Plan in November 2004.

The evaluation included: A Geographic Information System (GIS) mapped location for each tree. A determination of tree condition and management needed for each tree. A monetary value calculated for each tree. And a management plan to address the needs of the individual trees and the urban forest in general. The complete Management Plan can be seen by clicking here: Street and Park Tree Evaluation for Cheyenne. The plan is 314 pages long and may take several minutes to load.

The boundaries of the 2004 inventory are: On the North - W. 8th Avenue, Evans Avenue and Pershing Blvd. to Converse Ave, On the East - Converse Avenue, On the South - the railroad tracks, and On the West - the residential area to I-25. Davey Resource Group evaluated 19,315 total sites which include: 7,718 street trees, 114 stumps along the streets and 973 possible planting sites along the streets (Since the cost of the tree evaluation was based on a per tree cost and per site cost, there are actually many more possible planting sites above the 973 identified). There are 11210 total trees (includes 709 trees planted Fall of 2004 after the inventory was complete) in city maintained public areas including parks, golf courses, cemeteries, Greenway, and around city buildings. The park tree total includes city maintained areas previously evaluated by Cheyenne Urban Forestry arborists last year.

In summary, the tree evaluation determined:

• 19,315 total sites which include: 7,718 street trees, 973 possible planting sites along the streets (Since the cost of the tree evaluation was based on a per tree cost and per site cost there are actually many more possible planting sites above the 973 identified), and 114 stumps along the streets. There are 10,501 total trees (not including 709 trees planted Fall of 2004 after inventory was done) in city maintained public areas including parks, golf courses, cemeteries, Greenway, and around city buildings. The park tree total includes city maintained areas previously evaluated by Cheyenne Urban Forestry arborists last year.

• The total value of the inventoried part of Cheyenne's street trees and the entire park tree population is estimated to be $34.5 million.  A good informational Website on the value of trees is:  Colorado Tree Coalition.

• There were 123 different tree species identified. Most species diversity was found in the Cheyenne Botanic Gardens.

• Populus species (cottonwood, poplar, aspen) comprise 19.8% of the inventoried tree population. Picea species (spruces) comprise 15.4%, Pinus species (pine) 13.5%, Fraxinus species (ash) 10.0%, Ulmus (elm) 8.2%, Malus species (crabapple and apple) 5.6%, Prunus species (cherry and plum) 4.7%, Gleditsia species (honeylocust) 4.5%, Acer species (maple) 4.3%, and Juniperus species (juniper) contributing 2.9%. These ten top genera comprise 88.9% of all the trees evaluated.

Pruning Trees

Here are two good websites pertaining to tree pruning:

Colorado State University Cooperative Extension

Pruning Shade Trees in Landscapes

USDA Forest Service

LICENSED COMMERCIAL ARBORISTS

This list constitutes the arborists that are currently licensed and insured according to the City of Cheyenne Ordinances. The Urban Forestry Division cannot endorse the quality of  work of any company or individual on any particular tree/shrub. The Urban Forestry Division suggests that consumers obtain several estimates, check references, and enter into a written contract before tree work begins.  

 As of April 1, 2006, all commercial arborists in Cheyenne are required to be Certified Arborists or Certified Tree Workers through International Society of Arboriculture, to be licensed in the City of Cheyenne.


The commercial arborist companies below have an International Society of Arboriculture - Certified Arborist
on staff, and are licensed by the city.

Every year, Cheyenne homeowners are inundated with advertising offering cut-rate deals from contractors for tree and lawn care services. As a service to homeowners, the Cheyenne Urban Forestry division would like to offer these consumer tips.

1. Request proof of licensing and insurance: All tree care and spraying operations legally operating in the City of Cheyenne must be licensed through the City Clerk's office and must have adequate insurance coverage. In addition, spraying operations must be able to show a current State of Wyoming Pesticide Applicator's License. These requirements are for your protection and do not necessarily increase the cost of a job. Avoid non-licensed and uninsured companies, as you have no legal recourse should damages occur. If an uninsured worker injures themselves on your property, you will most likely have to pay the medical costs.
   
2. Ask for written estimates: Obtain several estimates, compare the work specified, and the completion date. If your trees are to be sprayed, find out what insect the company is spraying for and what time of the year is the optimum time to control that insect. Most insects are only effectively controlled during certain growth stages, therefore only certain times of the year. Beware of individuals that required payment "up front". Services should not be paid for until all work is completed to your satisfaction.

Call the forestry office (307-637-6428) to obtain a copy of the free International Society of Arboriculture brochure " Why Hire an Arborist".

 Publications

Lions Park Tree Walk - Available in Cheyenne Urban Forestry Office in Lions Park.
Drought and Trees - Developed by Cheyenne Community Forestry Committee
Suggested Trees and Other Plants for Cheyenne

Publications from International Society of Aboriculture:
          Available in Cheyenne Urban Forestry Office in Lions Park.
City Boulevard Tree Care Responsibilities
Tree Ordinance
Why Hire an Arborist
Mature Tree Care
Why Topping Hurts Trees
Benefits of Trees
Buying High-Quality Trees

Several other brochures and informational papers are available and too numerous to list covering insects, diseases, planting, pruning, iron chlorosis, and tree maintenance. Available in Cheyenne Urban Forestry Office in Lions Park.