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What should you look for when purchasing a tree at your local garden center or nursery? The Agricultural Extension Service at The University of Tennessee offers these answers:
Check the trunk for bark scrapes by machines and environmental injuries such as sunscald and animal damage. Trunk wraps may hide wounds, incorrect pruning cuts and insect injuries. Wraps should be removed and the trunk inspected. Avoid trees with obvious insect or disease problems. Look for signs of vertical trunk cracks, usually found just below branch unions. These cracks are major starting points for fractures of branches and trunks. Select trees that have only one main trunk that is straight and has not been pruned back at the top.
Look to see if there are broken branches, indicating poor or rough handling. Branches should not cross or rub. Branches should be spaced 8 to 12 inches apart, evenly distributed on all sides of the central leader, and should be growing on the upper one-third to one-half of the central leader. Avoid trees with branches that have been excessively pruned back. Weak branch unions or v-shaped branches occur where two branches or a branch and a trunk squeeze together. The squeezing increases during diameter growth, creating cracks and potential breaking of the limb during storms. One of these squeezed branches should be pruned. Avoid purchasing trees with these weak branch unions.
Avoid plants that appear wilted or with off-color foliage. These are indications that tree care has not been optimal or that something is wrong with the root system. Desirable trees possess good foliage color and full-sized leaves.
To check for well-rooted trees, grasp the trunk of the tree near the base and try to move the tree in the root ball or container. Well-rooted trees should not create a hole in the soil when the stem is shaken. The container and the tree should move as one. Remove the container without harming the tree and examine the roots. Healthy roots are firm and usually lighter in color than the surrounding soil. There should be no odor or mushiness. Carry trees by their container or root ball rather than by their trunks to avoid damaging their root systems. The roots of B&B trees may be inspected in much the same way as a containerized tree. The ball should not have cracks in the soil or large clumps of loose soil. If it does, these are indications of improper handling.
Deciduous trees drop their leaves in the fall and grow new ones in the spring. The vitality of these trees is difficult to determine in the early spring before leaves appear. To check the health of these trees in early spring, examine several branches. Scraping the bark of a live branch with a fingernail should show green tissues beneath. If not, the branch may be dead. Live branches of most trees are quite flexible. A dead branch will usually be shriveled and will snap and break. Buds should be swollen and plump. The tree’s previous growth can be checked by observing the bud scars on the branches. Very little growth between scars (less than 4 inches) may be a sign that the tree is in trouble.
Small trees adapt quicker to planting than larger trees. Special care must be taken when planting a large tree because its root system is not in balance with the aboveground portions of the tree. Much of the lateral root system, perhaps up to 70 percent, was left in the nursery bed during uplifting. Thus, extra maintenance, primarily judicious watering during dry periods, is required to reduce stress and overcome transplanting shock to a new location. A common practice is for nurseries and garden centers to have end-of-the-season sales of trees. Be careful in purchasing these trees. Many of these trees were leftover from sales during peak times and have not received the proper handling, care and watering throughout the summer to maintain tree health. Once deciduous trees lose their leaves, it is difficult to determine their tree health. Trees that were lifted from the nursery in the spring should have been planted months ago. Holding these trees over the summer increases their stress and decreases survival. Buy nursery stock from reliable nurseries that are knowledgeable about the trees they sell, offer tree guarantees and practice proper handling and care of their nursery stock.
What to look for when inspecting trees for purchase: - Overall health and vigor with at least 4 to 6 inches of growth from the previous growing season to the end of the twig. - Symmetrical form with a balance between height and crown spread. - Freshly dug trees grown for your particular use in a climate similar to yours. - Well-spaced branches that are evenly distributed around the trunk. - Well-developed buds. - Branches and crown in the upper half of the central stem. - No branches with a narrow angle or v-shaped notches. - No sign of insects or diseases (egg masses, cankers, sunken areas, grubs or borers). - A single, straight trunk free of mechanical wounds and wounds from incorrect pruning. - A well-developed root system, but not a dense mass that is pot-bound or with girdling roots. - A rootball that is proportional to the size of the tree.
Plant high-quality stock to avoid future tree hazards associated with your tree. Planting poor stock will probably lead to more expense in the long run because of increased maintenance and a shorter life span. The best procedure is to purchase trees from a reputable nursery, establish careful specifications for your purchased tree and obtain a warranty for your tree.
All trees have their good and bad characteristics. Rarely does a tree throughout its lifetime satisfy or even maintain the objectives for which it was planted. Trees become larger over time, often outgrowing their original growing space both above and below ground. Some trees also produce fruits or seeds that may be troublesome to the homeowner. An example of a tree planted in Middle Tennesseee to fulfill a need, but later presenting problems is silver maple, which grows and provides shade quickly. However, it is a short-lived tree with brittle wood prone to limb breakage during wind and ice storms. Another example of a problem tree for Middle Tennessee is sweetgum, which is a handsome tree with attractive foliage. But its root sprouts and the seed capsules (sweetgum balls) can create a nuisance. Hare are some other trees with problems that Middle Tennessee homeowners should consider before planting.
White pines are frequently planted in Middle Tennessee for borders and screens along property boundaries. Although the tree forms an excellent screen, its fast growth and large size often exceed the growing space provided. Removal of large trees is expensive. Tennessee is the southern extremity of the growing range for white pine. Generally, its habitat is at the cooler, higher elevations. Because of its wide genetic diversity, the planting range has been extended to Middle Tennessee. However, some trees are not able to tolerate the warmer and drier environments. The results are heat and moisture stress which makes them susceptible to common pests such as aphids, sooty mold and pine bark adelgid. The white pine weevil also attacks young trees, killing the terminal leader and causing trees to become stunted and lose apical dominance. One should expect that some white pines will succumb when planted beyond their natural range. Those trees can easily be replaced with another white pine or another species such as Yoshino Japanese-Cedar, Foster Holly or Burford Holly. The large size of white pine often precludes planting it in urban areas.
Hackberry trees are susceptible to ice damage with their brittle wood, wide branching pattern and weak branch crotches. The thin bark is susceptible to injuries or wounds that can lead to extensive decay. Surface roots can raise sidewalks and interfere with lawn mowing. The fruits are messy and birds spread the seed widely. However, hackberry seeds are a major source of food for birds in the winter. The best use of hackberry is along the margins of woods or in open lawn areas, but not near pavement or utility lines.
Both trees are exotics that naturalize in uninhabited landscapes and become weed trees. Abundant seeds create many unwanted seedlings. Both species are also prolific root sprouters, causing poor tree form. The fruit, twigs and leaves cause significant litter. Weak wood and drooping branches are susceptible to breakage. Surface roots are a nuisance for lawns. Other trees provide many more benefits to urban landscapes than these.
Tree-of-heaven is a non-native, rapidly growing tree that has a pinnately compound leaf resembling black walnut. A rancid smell is produced when limbs are broken. The weak wood is susceptible to limb breakage. Tree-ofheaven is considered a weed tree, spreading prolifically by seed and root suckers. Roots will uplift sidewalks. This species has little leaf color in the fall. Due to its rapid growth, tree size can become a problem. Tree heights of more than 80 feet and diameters more than 3 feet are common. Tree-of-heaven is an invasive tree with few benefits for urban landscapes, and should not be planted.
Only male ginkgos should be planted, as the female produces a messy, foul-smelling fruit in late summer. The only way to select a male plant is to purchase a cultivar from the nursery, because no reliable method exists to distinguish a female plant until it fruits (often 15 to 30 years). Reliable male cultivars are Autumn Gold, Princeton Sentry and Saratoga. The large size of ginkgo often outgrows the original planting site.
Virginia pine is a scrub tree that retains its lower branches and forms irregular crowns. The shallow roots of Virginia pine make it susceptible to windthrow. Branch breakage from ice is common. This tree also produces many prickly pine cones. Virginia pine should be avoided except for the poorest sites where other trees will not survive. Shortleaf pine is recommended for planting in urban areas instead of Virginia pine.
The willows are fast growing trees that often expand beyond their original growing space. Roots affect underground water, sewer and septic lines. The willow’s brittle wood is susceptible to ice and wind damage. Trees are shortlived, from 20 to 30 years. Willows are very tolerant of wet and poorly-drained sites. Willow is not a good tree for residential settings because of its large, lateral size. If a weeping form is desired, select from weeping cherries, mulberry or birch.
Black locust is not recommended for urban plantings. Birds widely disperse the seed, causing a lawn problem. The root system has the propensity to sprout. Branches and twigs also have thorns. Black locusts are highly susceptible to locust borers that often cause premature death of the tree. Locust leaf miner is prevalent late during the growing season, creating unsightly brown foliage. However, black locust is a legume that is excellent for steep banks and harsh sites. Thornless honeylocust varieties are suggested as an alternative to black locust for urban landscapes.
The wood is brittle and major limbs split from crotches, causing damage during wind and ice storms. Fruits and twigs cause significant lawn litter. Branches droop and require pruning. Surface roots lift sidewalks and pavement. An elm leaf beetle often defoliates Siberian elm. Other elm species such as lacebark elm should be planted rather than Siberian elm.
Mimosa is a fast-growing, short-lived (10-20 years) tree with many seed pods that litter the tree and the ground.The seeds often germinate and resprout, causing a weed problem in lawns. The wood is extremely light and brittle.The spreading branches and multiple stems of mimosa are prone to breakage. Insects (webworms), vascular wilt disease and stem breakage contribute to its limited lifespan. Planting mimosa should be avoided. Crapemyrtles and smoke tree are desirable substitutes.
The dense, evergreen foliage and oval to pyramidal form of Leyland cypress are frequently used as a screen, hedge or windbreak. This rapidly-growing tree quickly outgrows its space in small landscapes and is too big for most residential landscapes unless it is regularly trimmed. Leyland cypress is relatively short-lived (25 to 50 years) and is not native to the United States. Three known canker diseases have been documented in Tennessee that affect Leyland cypress. Bagworms are also a serious insect pest that can defoliate the tree. Considering the high maintenance associated with Leyland cypress and its sensitivity to insects and disease, this tree should be saved for large-scale landscapes where it can be allowed to develop into its natural shape without the maintenance required in residential settings.
Cottonwood has weak wood, shallow roots and is easily damaged in storms. This species is generally short-lived, and because of its fast growth and large size, having it removed is expensive. Leaves often drop from the tree beginning with the first dry period of summer and continue dropping through the fall. Cottonwood becomes a large tree quickly and is not recommended for residential settings. Hybrid poplars are frequently promoted for rapid growth as potential shade trees. These trees are not recommended as shade trees because they are short-lived and have brittle wood. Most hybrid poplars are used as windbreaks in the Midwest where droughty soils and low rainfall limit their rapid growth or in short-rotation fiber farms for pulp and paper production.
Tennessee is the extreme southern growth range for this species. Paper birch is vulnerable to stresses from drought and hot temperatures that make it highly susceptible to secondary attacks of several insects (leaf miners, skeletonizers and borers) and disease infections by fungi-causing cankers. The lifespan of paper birch in Tennessee is generally less than 25 years. Paper birch should only be planted on moist, welldrained soils where regular watering and fertilization can take place.
The shallow, fibrous root system combined with the dense shade canopy make it virtually impossible to grow grass below Norway maple. These trees are susceptible to girdling roots. The roots wrap themselves around the base of the tree, restricting growth and eventually choking the trunk and killing the tree. Norway maples may create an insect problem with aphids and the resulting honeydew. Norway maple will crack sidewalks. The tree is not heat tolerant in Middle and West Tennessee. The best management of Norway maple is to avoid planting too many in one location, give each plenty of room to grow, keep trees away from pavement and inspect for girdling roots.
Both trees are considered soft maples with shallow, dense roots that often clog sewer lines and septic tank drain fields and lift pavements. The wood of both trees is extremely weak and vulnerable to wind and ice damage. Fall leaf color is minimal. These trees produce a large seed crop and are short-lived (25 to 40 years). Branches droop as the trees grow, requiring pruning. Silver maple and boxelder are highly susceptible to an assortment of mites, aphids and scale. The primary advantage of both trees is their fast growth for shade, but problems outweigh advantages.
Pin oak becomes a very large tree and should only be planted in areas greater than 600 square feet. The primary difficulty in East and Middle Tennessee is iron chlorosis of leaves on alkaline and limestone soils, causing leaves to turn yellow. Trees with chlorosis will decline in vigor and possibly die. Lower branches also droop and brown leaves persist on the tree during the winter. Pin oak produces many acorns. Pin oak is a wonderful urban tree where adequate space is available for full development and where soils are in the
Lombardy poplar is a short-lived tree planted primarily for its upright columnar form in windbreaks and screens. Although it grows fast, the tree is highly susceptible to stem canker disease that usually infects the tree at 10 to 15 years. The lifespan of the Lombardy poplar rarely exceeds 20 years. Choices of other trees to plant with this crown form include the ‘fastigiate varieties’ of hornbeam, alder or oak. As they mature, many trees produce seeds and fruits that may be a nuisance to homeowners. Nuts from hickories and walnut, acorns from oaks, sweetgum and sycamore balls are a few of the antagonists. Fleshy fruits from trees such as cherry and crabapple can also be messy and bothersome.
Here is a list of some of the nurseries and garden centers serving Middle Tennessee:
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