Ornamental Trees Flashcards
Hedge Maple
Acer campestre
Plant Description
Acer campestre is a small to medium sized (25 to 35 feet) deciduous tree traditionally used for hedge rows in Europe. It has a densely branched canopy with branches low to the ground, making it an ideal selection for screens and hedges. It will sucker from its root system to create a colony. If the lower branches are pruned up it makes an attractive, small tree suitable for modern small lots. It has a naturally pyramidal to rounded form. It is tolerant of poor soils, including highly acidic or alkaline soils, dry and compacted soils.
The dark green leaves are 2-4 inches long with 3-5 lobes. The petiole is long (2-4 inches), and when the petiole is broken off from the stem it weeps a milky white sap. The fall color is yellow and not spectacular. Small and inconspicuous yellow-green flower clusters appear in early spring. These are followed by 1 1/2 inch long samaras whose wings form a straight line or arch upward.
Landscape Use
As the common name suggests, Hedge Maple is an excellent selection for a screen or hedge due to its dense canopy and low branching habit. It is especially attractive in this role because of its hardy constitution. It is also an attractive lawn tree or small shade tree if it is trimmed up.
Paperbark Maple
Acer griseum
Plant Description
Acer griseum is a small deciduous tree, reaching 30 feet high with a slightly narrower spread. It is noted for its ornamental bark, which exfoliates in a manner similar to the many Birch species. It prefers moist, well-drained soil and will struggle under heavy drought conditions.
The most striking feature of Paperbark Maple is the exfoliating bark. The bark is a rich cinnamon-brown color that peels away from the stem in sheets. The bark begins to exfoliate on young branches (by third year), so this decorative feature appears throughout the canopy of the tree. Bark that is not exfoliating is smooth and shiny - and retains the deep cinnamon color.
The blue-green leaf is 3-6 inch long and trifoliate, with each leaflet being elliptic or ovate in shape. The margins of the leaflets have large, distinct teeth. The petiole is quite long (2-3 inches) and very pubescent. In fall the leaves turn anywhere from bright red to a mottled red. The samaras are 1 to 1 1/2 inches long, with the wings arranged at a little less than a 90 degree angle. The samaras is slightly pubescent.
Landscape Use
Acer griseum shines as an ornamental specimen tree, where it has the opportunity to stand out and be appreciated for its ornamental characteristics. I have seen them used as street trees and they seem to perform fine, though they probably need a wider parking strip or planter to grow well.
Norway Maple
Acer platanoides
Plant Description
has become one of the most over-used trees in the modern landscape due to its hardy constitutions, quick growth and that it is fairly pest free. It is a large shade tree (40-60 feet tall and wide) with a round form and dense branching habit. The canopy casts very deep shade, and will often cause the grass beneath the tree to thin due to a lack of sunlight. The bark is unremarkable and has a series of tight and shallow ridges and furrows. It is grey-brown in color.
The leaves are large, 4 to 7 inches long and wide, and are arranged oppositely on the stem. The petiole is also long and can reach up to 4 inches long. They have five lobes, the middle three being the largest and similar in size. The margin of the leaves is smooth, though rippling of the leaf edge can make the margin appear to be slightly undulate. The leaf is dark green and glossy. Fall color is yellow, but it is often less than impressive. The glossy samaras are 1.5 to 2 inches long and are arranged in just slightly less than a straight line.
Despite its many admirable qualities, there are some important drawbacks to the Norway Maple. It can become invasive due to its many seedlings that grow up around it, and removing these seedlings is a constant maintenance task. It also has a shallow root system which will buckle sidewalks and interfere with lawn.
Landscape Use
It is an excellent shade tree and is a suitable selection for larger residential lots as well as commercial projects. Because of its shallow root system it should not be used in parking strips or as parking lot trees.
Points of Interest
Verticillium wilt can be a problem. While it is currently free from any major pest population, the over-use of Acer platanoides is likely to lead to decimation of the population by some disease or insect in a similar manner to what was seen with both the Elm and Ash.
Notable Cultivars
Crimson King: Extremely popular due to its rich maroon colored leaf. It may experience some leaf scorch during the middle of summer here. It reaches 40-50 feet tall.
Emerald Queen: Emerald queen has a good upright oval form and dark green leaves. It has a good yellow fall color. Reaches 50 feet high.
Drummondii: A variegated variety with light green leaves with creamy margins. Reaches 35 feet high.
Columnar: An upright branching tree that forms a dense column of foliage. It can reach as high as 50-60 feet tall, with a spread of 15-20 feet.
Globosum: A strange looking tree that has a very formal globular canopy. It looks as if it has just recently been pruned to shape. Much smaller than the regular species (15 feet tall) and also slower growing.
Parkway: Another upright form of Norway Maple, though not as pronounced in form as Columnar, it reaches only 40 feet tall with a spread of 25 feet wide.
Red Maple
Acer rubrum
Plant Description
Acer rubrum is a popular deciduous shade tree that is cold hardy and fast growing; and famously has bright red fall color. Do not be mistaken by the common name of Red Maple and take it to mean that the leaf is red. In fact, the most popular red-leaved varieties of large maples are cultivars of Acer platanoides. It grows 40-60 feet high with a slightly narrower spread. The bark is gray-brown in color and becomes scaly as the tree matures. The young bark is more attractive as it is a silvery color and smooth.
In the early spring the tree puts form somewhat showy red flowers at the buds. Up close, the flowers are not particularly attractive, but at a distance they create a fair effect on the tree. Following the flowers, 2-4 inch long green leaves emerge (new leaves may be tinged with red overtones). The leaf has three lobes, though five-lobed leaves may sometimes develop, and a doubly-serrated margin. The underside of the leaf is a silver-gray color. The petiole is 2-4 inches long and is often red. In fall the tree puts on a spectacular show as the leaves change to a very bright red color.
The samaras are 1 inch long and the wings appear to be droopy. The wings may have a red hue, but the coloring is not dependable.
Landscape Use
Red Maples are very popular as shade trees and parking strip trees. They work best when put somewhere where they can show off their fall color.
Points of Interest
It is becoming increasingly popular across the country, but it can struggle in our climate because it frequently develops magnese chlorosis in our alkaline soils, followed by leaf burn, defoliation and die back.
Notable Cultivars
Red Sunset This variety produces some of the best fall color. It also has an attractive pyramidal or oval shape. Grows to 45 feet high and 35 feet wide.
Acer x freemanii - Armstrong A hybrid cultivar of Red Maple and Silver Maple. It grows 50 feet high and 15 feet wide. Unfortunately the fall color on the Armstrong Maple is inconsistent, and often consists of a mottled mix of orange and yellow. The leaves have five lobes.
Acer x freemanii - Autumn Blaze Also a hybrid of the Red and Silver Maples, it has long-lasting red fall color and a good form thanks to a strong central leader. It grows to 50 feet high and wide.
Purpleblow or Shantung Maple
Acer truncatum
Plant Description
Acer truncatum, Purpleblow or Shantung Maple, is a small maple that grows 20-25 feet tall. It could be considered an ornamental tree because of its attractive leaf and good fall color. It is more often used in a much more utilitarian manner as a lawn tree or street tree. It is an attractive tree, with a rounded form, dense canopy and a regular branching habit. It is hardy and drought tolerant, adapting to many different types of soil and climate conditions.
Young bark has a purplish overcast to it, from which the common name is derived. As the bark matures it develops a gray-brown color and the bark develops and ridged and furrowed appearance.
The leaf is 3 to 5 inches wide with five lobes and a smooth margin. Each lobe has a triangular shape, creating a very clean and symmetrical looking leaf. The leaf is an attractive dark green in color. Leaves are arranged oppositely on the stem. The fall color is a lovely mixture of yellows, oranges and reds The samaras are 1 1/4 inches long, green in color and the wings hang at a 90 degree angle.
Landscape Use
Its compact size makes it a good selection as an ornamental, street or lawn tree.
Points of Interest
The actual species is difficult to come by as it is not readily available. When I enquired as to the reason for this, several growers in the Northwest told me that the tree grew too vigorously in their mild climate and became gangly.
Notable Cultivars
Pacific Sunset: A hybrid with Acer platanoides, this is the most popular form of Purpleblow Maple. It has an upright form with a fine branching pattern. Grows to reach 30 feet tall. Unfortunately the leaves are much closer to Acer platanoides instead of Acer truncatum.
Norwegian Sunset: Also a hybrid with Acer platanoides, it grows to be 35 feet tall. It has an upright form with a good branching habit.
Catalpa
Catalpa speciosa
Plant Description
Catalpa is a large (40-60 feet high and 20-40 feet wide) and beautiful shade tree that is underutilized in the landscape. It typically has a strong upright form that, at maturity, will tower over the landscapes. The form is very variable, and often the trees end up with a rugged but picturesque form. It deals well with difficult conditions and is adaptable to nearly any soil and moisture condition. It has a fast growth rate and will quickly fill into a spot within a few year’s time.
The large leaf is true green to lime green in color almost tropical in its appearance. The leaves can be up to a foot long and have an elongated cordate shape. The large leaves give the tree a very lush and coarse texture. The leaves are often arranged in whorls, but can also be arranged oppositely.
During the early summer, large (2 inch wide or larger) white bell-shaped blossoms appear profusely on the tree. They have a yellow throat with red spots that give them a very tropical look. The flowers form in large panicles held above the leaves. Towards the end of summer, long skinny fruit capsules form on the tree. Theses capsules are stiff and can grow to 20 inches long. They are green during the summer, but turn to brown in the fall and persist into the winter.
Landscape Use
Use as a large shade tree both in a residential and commercial setting. It could be used as a parking strip tree in large parking strips (8 feet or wider), but will buckle sidewalks in smaller ones. It is great selection to use along the edge of a property in combination with other large trees and shrubs to provide seasonal interest.
Points of Interest
Dirr is less than enthusiastic about Catalpa, but it is a great performer in our climate and its planting should be encouraged. Leaf spot and wilt can be a problem, particularly on young specimens.
Hackberry
Celtis occidentalis
Plant Description
Celtis occidentalis, or Hackberry, is a tough and hardy tree with a fast growth rate. It grows 40-60 feet high with an equal spread. It can be a bit wild looking in youth, but matures into a strong upright tree with arching branches. The bark is gray in color and has protruding cork growth that is reminiscent of a bad wall texture, unique but not particularly attractive. While not the most attractive tree, its ability to put up with almost anything makes it a good selection for difficult spots.
The green leaves are obliquely ovate in shape, with an elongated tip, and arranged alternately on the stem. They are 2-5 inches long with a serrated edge. In fall the leaves turn a dull yellow color. In the fall, red drupe fruit forms in small clusters. The fruit is edible and has a sweet date taste, though I know of no one who eats them other than birds. The fruit will drop, but the tree is usually pretty well cleaned by wildlife.
Landscape Use
Use in the difficult situations such as in hot and windy spots or open fields. Its ornamental failings limit its use in most residential settings.
Points of Interest
Hackberry Nipple Gall is a major ornamental disease that strikes Hackberry. Insect larvae feeding on the leaves causes the leaf tissue to swell into a nipple-like protrusion on the leaf. It is not damaging to the tree, but is unattractive.
Green Ash
Fraxinus pennsylvanica
Plant Description
Fraxinus pennsylvanica is a large (60-70 feet high, 2/3 as wide) shade tree that has been popular as a residential and civic trees for centuries. Unfortunately, its popularity has led to it being overplanted and populations across the nation are now being ravaged by various pests and diseases. The main branches have a good upright branching habit with while younger branches exhibit a mild weeping habit with the branch tips bending upwards at their tips. It is a very diverse tree, capable of handling many climate, soil and moisture conditions.
The 8-12 inch long leaves are odd pinnately compound with 5 to 9 leaflets leaf. Each leaflet is 2-5 inches long, ovate to lanceolate in shape and usually have a serrated margin. Leaves are arranged alternately on the stem. The leaves are an attractive rich green color, and in fall turn a good yellow color.
Female trees produce narrow samaras (1-2 inches long) profusely in large clusters. The seeds are a very light green when when they first emerge and turn light brown as they mature. Ash tree that seed can be both messy and a nuisance, as young starts will begin to grow rampantly.
Landscape Use
Ash is extremely versatile and is popular for use as a shade tree, lawn tree, street tree and for civic and commercial projects. Its relatively short life-span makes it less attractive as a street tree and for use in other civic locations, but it is still used frequently.
Points of Interest
Partly due to the over-planting of Ash trees in the last century, there has been a proliferation of diseases that are taking a serious toll on Ash tree populations. Currently most problematic is the Emerald Ash Borer and Verticillium wilt. Although a hardy and attractive tree, there are other trees that can be selected without the same liabilities.
Notable Cultivars
Marshall’s Seedless: An old and popular form, this male selection has glossy leaves and most importantly it is seedless. Grows 40-50 feet high.
Patmore: Patmore is an improved form of Marshall’s Seedless that is slightly more upright in form and has shown to have improved insect and disease resistance. Grows 50-60 feet tall, but more slowly than other Ash trees.
Kentucky Coffeetree
Gymnocladus dioicus
Plant Description
Gymnocladus dioicus, or Kentucky Coffeetree, is a little used large deciduous tree that grows 60-75 feet high and 2/3 that in width. It has an irregular branching habit that gives it a rugged and picturesque appearance, especially in winter. It has shown the ability to adapt to a wide range of soil conditions, but performs best when given ample moisture.
The dark bark is a ridged and furrowed, with the ridges often appearing wavy or twisting in form. Young branches quickly develop the bark pattern. The large leaves are bipinnately compound and can reach up to 3 feet in length and 2 feet in width. The leaflets are elliptic in shape They are a deep green in color and emerge late in spring. The fall color is inconsistent, but can be a rich yellow color.
Large panicles of creamy green flowers appear in late spring. The individual flowers are small and are not considered an important ornamental feature. In late summer and fall, pea-pod seeds form on the tree. These can very from 5-10 inches, with female trees producing shorter pods. They are pubescent and green during the summer, but ripen to a rich reddish brown in the fall. Young tree do not produce fruit, and on mature trees, large crops of fruit are produced in 2-3 year cycles.
Landscape Use
This interesting tree is a good selection for a shade tree and is also a good choice for a park tree. I would not recommend it for use as a street tree.
Points of Interest
It can be quite a messy tree because it drops its leaves, rachises and fruit at different times, meaning multiple clean-ups are needed.
London Planetree
Platanus x acerifolia
Plant Description
Platanus x acerifolia, or London Planetree, is a large, stately and beautiful tree. It can reach 70-100 feet high with a spread of 65-80 feet, though the largest ones I have seen in the valley are probably only 50 feet, and tend to be more spreading in form. It has a moderate to fast growth rate. The large branches create an open form under the canopy that highlights the exfoliating bark that the tree is famous for. It prefers well-drained soils but is extremely adaptable to any soil type except for boggy soils. There is debate about how cold hardy it is, though there enough beautiful specimens in Cache Valley to conclude that it will perform well here.
The bark of the Planetree is its foremost ornamental feature. On the trunk and mature stems the bark exfoliates in plates, creating a striking pattern of brown, tan, yellow, cream and olive colors. The bark makes provides good winter interest, and the snow resting on a tree is a picture worthy of a Christmas card.
The leaf is large, 6-7 inches long and dark glossy green. The leaves have 3 to 5 triangular lobes and can easily be confused with a maple leaf. The margin is has large serrations. In fall the leaves turn a mixture of yellows and browns.
During the summer, 1 inch diameter fruit appear in pairs on the tree. The seeds are covered with small spikes that harden when the fruit dries and turns brown. Probably every child in America has played with the seed balls of a Planetree at some point. Typically the fruit will persist on the tree into the winter, but enough falls to the ground that it would be dangerous to walk under a Planetree while barefoot at the end of the season.
Landscape Use
Its stately nature makes Platanus x acerifolia an excellent choice for an isolated shade or lawn tree where one can appreciate its form. Its tolerance of poor conditions makes it a good choice for parking strips, but a parking strip would need to be around 8 feet wide in order to avoid buckling of the sidewalk as the tree matures.
Points of Interest
Anthracnose can be a problem during wet springs.
American Linden or Basswood
Tilia americana
Plant Description
Tilia americana, or American Linden, is a long-lived and large shade tree (60-80 feet tall and half as wide). When the tree is young it has a pyramidal shape, but will eventually mature to a more ovate shape. It is faster growing and has a more open branching habit than other species of Tilia. It can tolerate some drought conditions, but it will perform better in more moist soils. The bark is gray-brown in color with flat-topped ridges that make it look as if someone has sanded down the outermost layer corky bark.
The large (4-8 inches long), dark green leaf is broat-ovate form with an obliquely cordate base. The margin is coarsely serrated. The leaf of Tilia americana is larger in size and more coarsely serrated than those of Tilia cordata. The leaves are arranged alternately on the stem on petioles 1-3 inches long.
Small, but strongly fragrant, flowers emerge in late spring. The flowers are a pale yellow or white in color. They hang in drooping cymes with up to 10 or more blossoms per cluster. The flowers are very attractive to bees and other pollinating insects, and it is best to keep the limbs of the trees pruned up in order to avoid walking through a swarm of insects. In late summer, 1/4 inch fruit appears in clusters on the tree. The fruit is a hard nut that cannot be crushed between the features (another useful method of differentiating between Tilia americana and Tilia cordata.
Landscape Use
Use as a shade tree in residential lots or larger campuses. I do not recommend planting it in particularly difficult locations. I have seen it used as a street tree, but I believe that Tilia cordata is a better selection for that role.
Points of Interest
It may develop stress in areas with high air pollution. Lindens are often the feeding ground of aphids, who’s voracious feeding on the leaves causes leads to a shower of sticky sap, called honeydew, on anything below the tree.
Notable Cultivars
Redmond: The most popular form, it has a distinctly dense, pyramidal shape. It grows smaller than the regular species, reaching 40-50 feet tall. It is one of the best cultivars of American Linden for use as a street tree.
Littleleaf Linden
Tilia cordata
Plant Description
Tilia cordata, or Littleleaf Linden, is a large shade tree, reaching 60-70 feet high with a width a little over half of that. It is a hardy and quick growing tree that performs admirably in some of the worst situations. It has a strongly pyramidal shape when young that matures to an upright-oval form. The branching is denser and more upright than Tilia americana.
The leaf is small to medium in size (1 1/2 to 3 inches long), about the same in width and arranged alternately on the stem. It is more rounded than the leaf of Tilia americana and more finely serrated. The base of the leaf is obliquely cordate in shape. The top of the leaf is a glossy dark green, while the underside is pale green.
The small flowers are light yellow to white in color and hang in drooping cymes during late summer. They are very fragrant and attract plenty of pollinating insects. Keep the limbs pruned up to avoid the clouds of bugs. Clusters of fruit appear by late summer and is smaller and not as hard as that found on Tilia americana. Each fruit cluster has a modified, light green leaf emerging from the base of the cyme. These light green leaves give the Littleleaf Linden and interesting color and texture contrast from the middle of summer until the leaves drop in fall.
Landscape Use
Tilia cordata is a very hardy tree that is ideally suited to use as a parking street tree or as a parking lot tree because of its ability to handle poor soil, pollution, and drought conditions. It also makes a good shade tree in either a residential or commercial setting. I have some neighbors that planted Littleleaf Lindens in their parking strip at the beginning of summer and never watered them. Three years later, all of the trees have survived (albeit with some dieback) and are now starting to thrive.
Points of Interest
As with the American Linden, Littleleaf Linden also suffers from aphid infestations in the spring, and the honeydew from the feeding aphids will leave a sticky residue on anything beneath the trees.
Without a doubt, Tilia cordata is becoming overused in our urban landscapes. It can be expected that a dearth of disease and insect problems, similar to what has happened to Ash and Elm trees, will be a problem in the near future.
Notable Cultivars
Greenspire: One of the most popular cultivars of Littleleaf Linden, it has a strong central leader and a good symmetrical form. Grows smaller than the regular species, reaching only 40-50 feet high and 30 feet wide.
