Category Archives: Tree Info

Alder

Alder

Alnus glutinosa

Fast growing oval shaped tree maturing to 50′ X 40′. Tree prefers plenty of moisture but will tolerate dry, compacted urban soils as well. Has moderate tolerance of salt and will grow in full sun or partial shade. Very attractive branching, leaf shape and nut-like fruit that hangs on through the winter. Does not attract wildlife and is not messy. Very good choice for the Front Range and transplants easily.

Common Problems

Environmental

No significant issues. Alders will tend to grow multiple trunks and can be left to do so for screening or ornamental purposes. They can also be pruned to a single leader.

Diseases

None of significance. However, in Europe a disease similar to the potato blight that has caused significant death among the Alders.

Pests

Aphids and Leaf Miners are sometimes found in low pressure populations but are typically not an issue.

Cultivars

Several available.‘Aurea’, golden yellow leaves; ‘Fastigiata’ — narrow, upright form; ‘Laciniata’ leaves not as deeply lobed, vigorous growth; ‘Pyramidalis’,upright or columnar form to 50 feet tall, 25 feet wide.

History and Use

The earliest fossils date back to the Miocene about 18 million years ago. It has been traditionally grown for timber and firewood. It is used extensively for soil stabilization along river banks and for soil reclamation projects after such disturbances as mining or logging. They are a nitrogen fixing species meaning they make the soil significantly more hospitable to other tree species wherever they grow.

Not native to North America. The Alder establishes well, especially along waterways and other disturbed wet sites where it will propagate easily and form pure stands or thickets. It can be harvested for excellent furniture and cabinet grade lumber (Alnus rubra reaching 120 feet in height). Very attractive, clean and smooth, grain which lends itself to a very stable final product.

Alders tends to pull minerals from the soil and store them in the cells of their woody architecture. The bark is known to be used for treating burns and infections because of its chemical make up.

Apple

Apple Tree Service

malus

A highly cultivated tree growing medium to fast and generally maturing to a round crown of 35′ X 25′. Prefer moist loam soils but tolerate alkaline, clay, dry and a bit of salt fairly well. Very showy spring flowers and edible fruit make this an attractive planting choice. There are many many cultivars of apple available. So many that we will discuss only edible apples here. See Crabapples for non-fruiting or flower specialty varieties.

Common Problems

Environmental

Structure pruning is very important from early on and should be done according to what the trees purpose will be. If the apple will be harvested the tree should be pruned to reduce height and encourage thick limbs in order to make picking practical and allow the trees architecture to support the heavy fruit. Prone to sucker sprouting at base and in the root zone of trees. Sunscald is common on newly transplanted trees, wrap trunks for 2-3 years.

Diseases

Fireblight, Powdery Mildew and some other fungus problems are common with these trees. Plant Resistant varieties available from most nurseries. Control through pruning and/or chemical applications is often recommended. Apple Rusts do occur with Hawthorn and Juniper as the alternate hosts but it is an uncommon occurrence.

Pests

Aphids and Wooly Aphids are a regular nuisance with these trees. The fruit is prone to Codling Moth which is very common and controlled with a pesticide treatment in the Spring.

Cultivars

Many are available: You can check them out at Creekside Nursery

History and Use

Apples have been hybridized over many thousands of years from an almost inedible small fruit into the many varieties we enjoy today. The wood is excellent for burning and if you can find a straight solid trunk it is a beautiful furniture grade lumber. Also used for wood turning.

Aspen

Aspen Tree Service

populus tremulus

Grows fairly quick with adequate water to 18’X45′. Aspen do well in the clay soils but water is the key and they are very thirsty trees. Winter watering is crucial.

Common Problems

Environmental

Roots like to surface and sprout making it ideal for fields and open spaces where this won’t be an issue. Wood is weak and tends to break easily under wind or snow loads. Pruning can help but planting with maximum distance to targets such as paths, structures and streets is best. Because this tree actually reproduces though root sprouting it is ideal to let as many sprouts as possible grow and replace the older stems (trees) that will die.

Diseases

Trunk cankers and leaf fungus (blights) are fairly common. Watering and fertilizing are the best deterrents. An anti-fungal or fungicide spray applied as the leaves begin to form in early spring will often reduce or eradicate leaf blights for the season.

Pests

Aphids are often present but pose little threat to overall health. Oyster scale and polar borer are often a problem as a tree ages or if it is stressed. Oyster scale can be treated by scraping off or with a systemic insecticide. Poplar borer is difficult to treat.

Cultivars

Pyramidalis’ Bolleana (white) poplar, A smaller more upright and narrow variety.

History and Use

This tree is found throughout the Rocky Mountains and is a major attraction in the autumn as the foliage turns to a vibrant yellow. A very popular landscape choice with a bad rap for its tendency to have problems with pests and diseases. This is true but almost always due to cultural issues like insufficient watering practices. Used in rustic furniture making.

Birch

Birch Tree Service

betula papyrifera

A medium size tree 40’X25’ with an elliptical shape growing at a medium rate and liking high moisture in a cool soil. Yellow in fall.. White flaky bark is chalky and exfoliates with horizontal black lines and eyes common. Trunk typically remains golden brown for the first ten years or so of life. Fall and winter watering very important.

Problems

Environmental

Susceptible to sunscald and leaf scorch. Avoid planting with direct exposure to the south and west sides. Watch for girdling roots at planting and root prune if necessary.

Diseases

Diseases are rare along the Front Range.

Pests

Bronze Birch Borer is a problem and should be treated preventively in the spring. Leaf miner is also an issue with this species but can be treated preventively and avoided.

Cultivars

Betula pendula ‘Gracilis’ or Cutleaf weeping birch is a more pollutant tolerant variety. Much more susceptible to Bronze Birch Borer and leaf miner. Bark does not exfoliate. Others also available.

History and Use

Can be tapped to make syrup from the sap, however the sap contains about 1/3 the concentration of sugar of that of the Sugar Maple. This is only done in Alaska and on a limited scale. The fibers from the wood can be used in paper making. The bark is an excellent fuel source for burning.

Black Locust

Black Locust

Robinia pseudoacacia

The black locust tree is a fast growing tree, maturing to 40-70’ x 40’ with an upright narrow and open canopy. This tree thrives along the Front Range as it is tolerant of a variety of environmental conditions including salt, compacted clay and drought stress. Bland to catchy yellow in the fall and gorgeous yummy smelling flower clusters in the late spring. Short painful thorns at the base of leaves and deep dark furrowing bark appear like crusty ridges from the base to the twigs where they hardly smooth out. Propagates through legumes in pods and through an aggressive sprouting root system.

Common Problems

Environmental

Prone to storm damage because of branch growth habits. Poor branch structure should be corrected through structural pruning every 3-5 years for the first 15-20 years of life. The seeds, bark and thorns are poisonous and should be kept from horses especially. If eaten by horses a vet check will likely be needed.

Diseases

Some cankers are rare. Powdery mildew and some leaf fungi are common often yellowing the leaves mid summer and causing them to drop. Treatment is rarely warranted.

Pests

The Black Locust Borer is a serious problem pest causing major mechanical wounding to the trees structural integrity on young trees and major stress on older ones. Should be controlled if tree has value.

Cultivars

Several available. The most popular is the ‘Purple Lobe’ which has brilliant purple flower clusters that smell wonderful in the late spring. Again, it is very susceptible to the borer.

History and Use

Traditionally used for many outdoor applications like fences, boats and nails because of its extreme hardness and resistance to rot. Also a huge favorite among honey bees who make a remarkable and sought after honey from the pollen of the Black Locust. Mistakenly named after the Mediterranean locust tree which has much religious historical significance.

Black Walnut

Black Walnut

Juglans nigra

Black walnut reach about 75’ x 60’ in size with a round to oval shape. This tree can be a fast growing tree when young with adequate watering, but typically is a slow growing tree as it matures. It has alternate, odd pinnatley compound leaves with 15-23 leaflets. They do very well in most soils and prefer full sun. They do not do well along streets or in compacted soils.

It produces commercially important nuts and the wood is highly sought for fine furniture and veneers. If you don’t mind the mess they are excellent landscape trees.

Formerly an excellent shade tree choice, caution should now be observed before planting this species because of the high susceptibility to Thousand Cankers Disease.

Common Problems

Environmental

Leaf Scorch is an issue when temperature are hot and there is not adequate soil moisture.

Diseases

The major disease to watch for in black walnuts is Thousand Cankers Disease. Please read about it in the “Tree Problems” section if you are considering planting a black walnut or already have one on your property.

Powdery Mildew can also be an issue if the spring is cool and wet. Other canker causing diseases and twig blights occur, but are less common along the front range.

Pests

Aphids are a very common nuisance among Colorado black walnuts. The walnut twig borer is a major player in Thousand Cankers Disease and trees should be closely monitored for them.

Cultivars

There are many cultivars and varieties of walnut.

History and Use

Black walnuts have a very rich history as shade trees, food producers and providers of beautiful wood used for furniture, veneers, instrument building and more. Very common street tree. Wood can be used in furniture and flooring.

Bur Oak

Bur Oak

Quercus macrocarpa

Bur oaks have a medium growth rate and can reach hefty sizes of 90′- 80′ in its native habitats. They are tolerant trees with alkaline, salty, clay and compacted soils being little hindrance. The trunk has deeply furrowed bark on a single stem. Autumn colors displayed by the lobed leaves are an unspectacular yellow to brown.

Common Problems

Environmental

With its weak wood and long horizontal limbs as it ages expect to see some storm damage from snow and wind load. This can be mitigated some with pruning, but generally bur oaks grow strong structure on their own. Directional pruning will be necessary over streets and walkways.

Diseases

Some problems with different fungi, but not seen often along the Front Range

Pests

Aphids and Leaf Miners are a minor problem that occasionally require control.

History and Use

Often sold as white oak in the form of lumber. Widely planted in the landscape and very important as a food source to animals in the forests.

Catalpa

Catalpa

Catalpa speciosa

Catalpas have elegant narrow and upright canopies that mature to about 50′ x 25.’ They are slow growing trees that prefer medium soil moisture. They do well in most soil types and are drought and winter tolerant. Catalpas have very large, heart-shaped, dark green leaves. The seed pods are very large and resemble cigars which remain through the winter and give the tree its second common name of “cigar tree.” Beautiful white clusters of trumpet-shaped flowers bloom in the late spring and make catalpa trees an appealing selection for the Front Range.

Common Problems

Environmental

Occasional structural issues that can be addressed when the tree is young with structural pruning.

Diseases

Some fungus problems occur, but not generally a problem.

Pests

Eriophyid mites can be an issue sometimes, but it are fairly uncommon.

History and Use

Catalpa wood has been traditionally used outdoors for things like railroad ties and fence posts because of its natural resistance to decay. It is also used for furniture making because it is a clear and fine looking grain and is stable. Anglers will seek out catalpa trees that are infested with Catalpa Sphinx Moth to use them as bait.

Cherry

Cherry

Prunus

Cherry trees are highly cultivated and can grow rather quickly depending on cultivar. They generally mature to a round crown of 35′ x 25′, but the mature size really depends on the variety.

Common Problems

Environmental

When planting, it is very important to examine the root ball for any girdling roots and to identify the root flare and position it properly in its new soil. Girdling roots can especially be a problem in container-bought trees.

Structure pruning is very important from early on and should be done according to what the tree’s purpose will be. If cherries will be harvested the tree should be pruned to reduce height and encourage thick limbs in order to make picking practical and allow the tree’s architecture to support the heavy fruit.

Diseases

Cytospora Canker is often found on trunks and limbs of cherry and other Prunus species (Plum, Peach and Apricot). It is a fungus that moves through the tree cambium causing branch die back and eventually kills the tree. Treatment for Cytospora Canker is best done through proactive cultural practices such as proper watering, pruning etc. Once established it is very difficult to control or eradicate. Powdery mildew and a few other leaf and twig fungi do occur on cherries. However, they can usually be controlled with early season fungicide applications.

Pests

Aphids, shothole borer and peach tree crown borer are all common with ornamental cherry trees. Pear Slug is also occasionally found on the leaves of plums and cherries which can cause partial or full defoliation, but is generally not detrimental to the tree if treated or if infestations are minor. All pests of cherry trees can be controlled with pesticide treatments in the spring and summer.

Cultivars

Several available.

History and Use

Cherry trees have traditionally been cultivated for fruit production, lumber production and as landscape assets for their beautiful flowers.

Columnar Hornbeam

Columnar Hornbeam

Carpinus betulus

Columnar hornbeam has columnar growth and reaches 35′ x 15′. Attractive white flowers bloom in early summer producing a “bean pod” which hangs onto the tree through the winter. This tree does well in drought and alkaline soils if root space is not confined in areas like parking lots and tree medians. Their dark, thick, heart-shaped leaves help to tolerate full sun and limited water. Columnar hornbeam is also tolerant of pollution.

Common Problems

Environmental

Restricted root zones from curb, pavement and sidewalks will cause trees to dieback. Intolerant of salt in the soil.

Diseases

Trunk canker has been found on this species. However, it is uncommon.

Pests

Occasionally attacked by two-lined chestnut borer. Japanese beetle is known to eat significant portions of the leaves.

Cultivars

Several available.

History and Use

Very desirable street tree for its upright form and tolerance of trimming. Has been used as a screen tree and in topiary for centuries. Pleaching is a technique employed by the hornbeam where single trunks are grown straight up and the limbs are trained to grow into adjacent hornbeams creating an elevated hedge. More common in Europe it is gaining popularity in the USA every year.

The wood is so hard it also known as “ironwood.” Traditionally, it was used as axe handles, wagon wheel spokes and often as cogs for various early industrial machines like steam engines. Iron took its place in industry as its price dropped and it became readily available.