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WOODY ORNAMENTALS: TREES, SHRUBS AND VINES |
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KEY CONCEPTS
II. Acquiring Woody Ornamentals
III. Planting Woody Ornamentals
IV. Maintaining Woody Ornamentals
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A regular program of maintenance is required for best results with any tree or shrub. This program includes irrigation during the early years, core aeration, mulching, fertilization, pruning and regular inspection for disease and insect problems.
Watering woody ornamentals depends on the species and the soil. Some plants tolerate dry conditions better than others. A tree growing in a fertile, well-drained sandy loam may become established in a year or two. This tree would require little supplemental irrigation. A shallow-rooted tree planted in a poorly drained, heavy clay may require supplemental irrigation for several years.
During the first 4 to 10 years after planting, trees and shrubs may require supplemental watering. After that, the amount of water required for a mature tree or large shrub is so excessive (40 to 50 gallons of water per day per tree) that supplemental watering may not be realistic.
The most critical season for supplemental irrigation is usually during summer. However, any time during the growing season when rainfall is inadequate for more than a week or two can create water stress. It is necessary to begin watering before soils dry completely. Probing the soil and feeling for moisture is a reasonably accurate way to determine soil moisture.
Water stress in late fall is not normal and has dire results when it occurs. Plants must have adequate moisture to tolerate the stresses of winter.
Most of the soils in Ohio are clay-based. The roots of trees and shrubs soon grow beyond the planting hole into native soil. In areas where building has occurred, topsoil is usually removed, leaving clay subsoil. Aeration and drainage are a problem. Grass roots compete with tree roots for nutrients, moisture and air. Deep core aeration lessens these problems.
In deep core aeration or vertical mulching, drill holes into the soil beginning 6 to 10 feet from the tree trunk and extending 4 to 6 feet beyond the longest branches. The holes are 1 to 4 inches in diameter, 12 to 18 inches deep and 1 to 4 feet apart. Removed the soil from the hole. One- to 2-inch diameter holes do not need to be filled. The wall of the hole will gradually collapse creating additional air space in surrounding soil.
The 3- to 4-inch diameter holes should be filled with composted organic matter. The organic matter can be mixed with an equal part of coarse aggregate, such as vermiculite.
Deep core aeration should be done when roots are actively growing. Early spring and late fall are good times to core aerate. The soil should not be excessively wet or dry. Core aeration is not necessary until the roots have grown out of the planting hole into the surrounding soil. As a regular maintenance activity, core aerate every third year. For trees under stress, more frequent aeration may be beneficial.
Apply a mulch 2 to 3 inches deep over the soil. Keep the mulch at least 3 inches away from the base of the trunk. The mulch will help retain moisture, moderate temperature extremes and reduce the potential for physical damage to the base of the trunk.
Mulching trees and shrubs has several benefits. Mulches retain moisture, suppress weeds, moderate soil temperatures and reduce physical damage from lawn mowers and string trimmers. Organic mulches slowly decompose adding organic matter to the soil. Organic mulches should be periodically renewed. Never exceed a total depth of 3 inches of mulch.
Landscape fabrics or fiber mulches reduce weed problems while allowing water to penetrate to the soil. Ideally, mulch the soil out to the DRIP LINE of the tree.
Soil and environmental conditions in a landscape may differ from those in a natural setting. The soil in most landscapes has been disturbed. It is often subsoil from excavation of the foundation. In a forest, leaves fall to the ground each year, returning nutrients to the soil. Growth is much slower in a natural setting, resulting in lower nutrient needs. Trees and shrubs often must compete with turfgrass for nutrients.
Landscape trees and shrubs must be fertilized for optimal growth. Application should be in late October through early December or from February through May, while the plants are dormant. Frequency of application is dependent on soil conditions. Annual fertilization is recommended in poor soil, while every other or every third year is adequate in good soil.
The fertilizer should have a ratio of 3-1-1 to 4-1-2. Availability of products vary. Look for 24-8-16, 18-6-12, 18-5-9, 15-5-5, 12-4-4 or a similar ratio. Application rates should be based on a soil test.
However, a general rate is 1 pound of nitrogen per 100 square feet for shrubs. The rate for trees will vary depending on application method and competition from turfgrass.
If turfgrass is growing under a tree, apply the fertilizer in core aeration holes or use liquid fertilizer injected into the soil. For trees that are mulched or have ground covers under them, see the following general recommendation:
- For trees under 6 inches DIAMETER BREAST HIGH (DBH) apply 1/4 pounds of nitrogen per every inch DBH.
- Trees over 6 inches DBH: 1/2 pound of nitrogen per inch DBH.
For instance, applying 1/2 pound nitrogen per inch DBH to a 6-inch DBH tree using an 18-5-9 analysis fertilizer would be calculated as follows:
6" (diameter) X 0.5 (rate) = 3.0 (amount of nitrogen)
3.0 (amount of N) / 0.18 (%N in 18-5-9) = 16.7 pounds of 18-5-9 fertilizer.
The fertilizer should be applied evenly under the entire CANOPY of the tree.
Applications early in the growing season can be split into 2 equal parts applied 6 weeks apart.
Fertilizer spikes are popular alternatives. Carefully read the package label to approximate application rate and nutrient analysis.
Commercial tree care firms offer nutrient injections. These are recommended only when the conventional methods are not possible. Trees surrounded by pavement are an example of when this may be necessary.
Pruning is the selective removal of plant parts: shoots, branches, roots, flower buds, seed pods or fruits. A regular schedule of maintenance pruning will reduce growth problems. Proper pruning will enhance a plant's appearance and health, while improper pruning will result in serious health and aesthetic problems.
Plant health is a primary reason to prune. Dead, diseased or injured parts should be removed. A dense canopy should be removed to improve sunlight penetration and air circulation. Crossing branches should be removed to prevent rubbing of the bark.
Training young plants will result in an excellent structure of branching. Branches should be well spaced and at the strongest angles.
Creating unnatural forms through pruning has been practiced for years. BONSAI, TOPIARY, ESPALIER and POLLARDING are high-maintenance endeavors that can create dramatic focal points.
Controlling growth is often necessary. Pruning to control the size of a plant results in high maintenance. An alternative is planting a species that only grows to a specific size.
Rejuvenating old shrubs is a challenging pruning project. A sparse or overgrown hedge can be rejuvenated by pruning back in late winter.
Improving appearance is a legitimate reason to prune. Suckers at the base of a shrub are ugly and should be removed.
Avoiding injury or damage by pruning is wise maintenance. Low branches can damage cars, poke people in the eye or be a hazard for the person mowing the lawn. Limbs hanging over utility lines, the house or other valuable property can be a liability.
Flowering and fruiting can be controlled by pruning. Flower buds can be removed to encourage more vegetative growth. Pruning can be used to stimulate flowering on some plants like wisteria and lilac. Selectively removing some flowers will result in others being larger or producing larger fruit.
The basic tools every landscape gardener should own are hand pruners, lopping shears and a pruning saw.
Hand pruners or pruning shears are used to clip off stems up to 3/4 inch in diameter. Scissor types with two sharpened blades that overlap when making the cut are recommended. The anvil pruners have one sharpened blade that cuts against a flat plate. Anvil pruners tend to crush the bark of the stem being cut. Ratchet or geared pruners add leverage and should be used to reduce the muscular effort required to make a cut, not to cut larger stems.
Lopping shears have long handles to provide leverage to cut through branches up to 1-3/4 inch in diameter. They are useful in rejuvenating shrubs.
A narrow, curved pruning saw is excellent for removing limbs up to 2-1/2 inches in diameter. A pruning saw can fit into tight spots and make clean cuts. Larger cuts should be made with coarse-toothed saws or chain saws.
If the effort to cut any stem is so much that the person resorts to twisting, the next larger tool is recommended. Follow safety precautions when using tools, because the injuries that can result from accidents are serious.
Hedge clippers or shears are not used for making pruning cuts. They make straight-line cuts without regard to nodes.
All pruning cuts should be made just above a node. Your cut may go back to a bud or to where a branch emanates from a larger branch. Leaving a stub results in the stub dying. These stubs are entry points for disease and insects.
When a cut is made, hormones are released that cause buds within a few inches of the cut to break and grow. This gives you great control over where to make a cut, since you can determine which buds are likely to sprout. Where possible, prune above an outward-facing bud.
The appropriate angle for a branch coming off the trunk is a 45- to 60-degree angle. This results in the greatest strength for the limb.
When sawing off limbs that are greater than 1 inch in diameter, begin by making an undercut about 2 inches out from the final cut. Then cut into the top of the branch slightly out from the first cut. Then make the final cut just out from the branch or ridge collar. This will prevent the branch from tearing bark from the trunk of the tree.
Begin pruning a tree by removing dead, diseased or broken branches. Then remove branches that go straight up (water sprouts) or point downward. Then look at the branch structure and remove branches that are or will eventually become crossing branches. The final pruning will be based on total tree structure and appearance.
Multistemmed deciduous shrubs benefit from the removal of the oldest stems at the base of the plant. This keeps the plant open and vigorous. Follow this practice on lilacs, forsythias, and mock oranges. Allow a few of the most vigorous suckers to remain as replacements for the old stems. For shrubs that have not been properly pruned for many years, remove no more than 1/3 of the largest stems in any one year. Continue this procedure for 2 more years to complete the rejuvenation.
Other maintenance pruning includes the removal of dead, diseased, crossing and broken branches. Long branches can be cut back to a bud or to the point of attachment of an outward growing branch.
[illus. from Cornell]
Prune most deciduous shrubs in early spring before bud break. Pruning in early spring will remove the flower buds of spring-flowering shrubs. Therefore, prune spring-flowering shrubs after the blossoms fade.
PRUNING NEEDLED EVERGREEN TREES AND SHRUBS
The needled evergreen trees of Ohio are conifers. They can be grouped by bud patterns. Some conifers have whorled buds and, therefore, whorled branching. These include pines, spruces, firs and Douglas fir. In these conifers there is normally one flush of growth in spring each year. Growth can be reduced and made fuller by pinching off 1/2 the length of the CANDLE before needles expand in mid- to late June in Central Ohio (a week or 2 earlier in Southern Ohio and a week or 2 later in Northern Ohio). Most of these conifers can only be pruned back into the previous year's growth. New buds will not break if you prune further back on a branch.
[illus. from Cornell bulletin]
The other conifer group has random bud placement. These are the yews, arborvitae, cedar, Chamaecyparis and junipers. Yews and arborvitae have latent buds on older wood. By cutting the plant back, these buds will initiate new growth. The junipers, cedars and Chamaecyparis do not have latent buds and can be pruned only within the needled portion of the branches.
Pruning should be done in late winter or early spring before growth begins. If a light pruning is necessary, it should be done in late June or early July.
PRUNING BROADLEAF EVERGREEN SHRUBS
Broadleaf evergreens generally require very little pruning. Pruning should be limited to selective pruning to improve the natural habit or to keep it in scale with surrounding plants. Prune after the flowers fade. Prune back to a branch or bud. It is recommended to remove spent flowers of azaleas, mountain laurels and rhododendrons by snapping them off by hand.
Rejuvenate large or leggy, broadleaf evergreens in early spring. Cut back 1/3 of the largest branches within 6 inches to a foot of the soil. Continue this process over the next two years. Apply fertilizer after rejuvenation pruning and before buds begin to grow.
[illus. Cornell bulletin]
Training plants into hedges must begin when the plants are planted. Always keep the top of a hedge narrower than the base, so all foliage is exposed to sunlight. Hedges may be sheared for a formal look or pruned to maintain the natural form of the plant. The formal shearing must be done 1 to 3 times a
year to maintain the formal appearance. The first shearing should be done shortly after spring growth begins. Then repeat the procedure in early July.
The primary reason to prune vines is to limit vigorous growth. Most pruning should be done in late winter or early spring while the plant is still dormant.
Vines that climb by HOLDFASTS should be pruned to remove dead wood or to limit growth. Twining vines are generally pruned to maintain a full covering of foliage. They tend to produce most of their foliage on the newer growth. Wisteria and clematis require special pruning techniques. Refer to the Fact Sheets on these two plants.
Knowing the common pruning mistakes helps gardeners avoid damaging plants when pruning.
Topping trees and shrubs is a major mistake. It results in a WITCHES' BROOM effect. Never cut all branches back to the same height.
Pruning causes buds to break. If pruning is done late in the growing season, the new shoots do not have adequate time to harden off for winter and dieback is likely.
Painting or putting pruning dressing on pruning cuts is unnecessary and may actually cause harm. Ultraviolet rays in sunlight are nature's disinfestant. The paint or dressing may seal in disease organisms and protect the organisms from the ultraviolet rays.
Making pruning cuts flush to the trunk destroys the tissue in the branch collar or ridge. This is the tissue that grows over the wound, sealing it naturally.
[illus]
Moving established plants in your landscape is a physically difficult task. When a tree or shrub is dug, as much as 98% of the roots are left behind or damaged. Root pruning can be done a year in advance to form a compact root ball of fibrous roots. However, it is still difficult to dig a solid soil ball with a shovel.
[illus from Cornell tree & shrub maintenance]
Begin by tying branches to prevent damage. Dig a trench around the area that is to be the soil ball. Undercut the soil ball. Slide a piece of burlap or heavy cloth under the soil ball and tie it around the trunk of the tree or shrub. Then slide the soil ball onto a snow saucer or similar device to make moving the plant easier.
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