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WOODY ORNAMENTALS: TREES, SHRUBS AND VINES |
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Woody ornamentals are trees, shrubs and woody vines. They are the backbone of the landscape. Used creatively, they define outdoor living spaces. Trees and vines add a vertical dimension to the landscape. Woody ornamentals are more permanent than the herbaceous, nonwoody ornamentals. They usually cost more and require more work to plant properly. For these reasons, it is critical that a gardener plan before planting. Choosing the right plant for the right place will save much effort, expense and provide long-term satisfaction.
A Master Gardener must know the
basics of selection, purchasing, planting and care of trees,
shrubs and vines. Trees are the number one topic of the
calls received at most Extension offices. It is, therefore,
imperative to have a basic knowledge of these important
landscape plants.
KEY CONCEPTS
I. Planning the Landscape
II. Acquiring Woody Ornamentals
III. Planting Woody Ornamentals
IV. Maintaining Woody Ornamentals
Return to Introduction
PLANNING THE LANDSCAPE
Planning requires knowledge of both the site conditions and the cultural requirements of plants. There are hundreds of species of trees, shrubs and vines available to the gardener. A gardener's knowledge grows with exposure to new plants and situations. Observing where plants do well in nature is helpful in expanding your basic knowledge of woody plants.
The first question to ask when thinking about planting a woody plant is, "Why is that plant going into that spot?" The plant must have a function in the location where it is to be planted. That function may be to look pretty. Looking pretty also could be stated as being an attractive specimen plant that draws the eye to a particular area of the landscape. A magnolia in full bloom can be used to lead the eye of a visitor to your front entrance.
Trees, shrubs and vines also are planted for practical functions. They are excellent for screening an ugly view. Vines can be planted and maintained in very narrow spaces and offer excellent screening. Trees and vines are often planted to shade a patio or the house. Well-placed trees and shrubs divide the landscape into areas for play, entertainment, specialty gardening (vegetable, fruit or cut-flower gardens) and yard maintenance (composting, propagating and heeling in).
Hardiness zone, soil conditions, moisture level and exposure are key factors in site analysis. Knowing these key factors permits gardeners to select the right plant for each site. Problems arise when these factors are not considered. Decisions should be based not only on the plants a gardener likes, but also on the plants that are appropriate and will do well under the existing conditions.
Hardiness is normally based on the average low temperature of winter. This is a critical factor. If a plant cannot survive the coldest winter temperatures for extended periods, it is not reasonable to plant it. While winter protection can modify cold hardiness to some extent, it involves additional maintenance and the risk of the plant's death.
Winter or cold hardiness is not the only concern. Plants must also be able to survive other seasonal conditions: summer heat, drought, rainfall and drying winds. These and other weather conditions affect hardiness. A plant cannot be considered hardy for an area if it cannot survive during all seasons. However, hardiness maps are based on winter conditions.
You must know which hardiness zone you live in. This would be easy to determine if there were only one hardiness map. However, there are three maps commonly used:
- Arnold Arboretum
- United States Department of Agriculture (USDA)
- National Arboretum
All three are valid, but be aware which map is being used in a reference or catalog since the zone number will vary.
Soil type is discussed in chapter 2, but you should be aware that soil affects plant hardiness. For example, a Zone 6 plant may be hardy in Zone 5 if it is planted in a sandy loam. However, if the plant is in heavy clay, that may retain too much moisture during winter, the plant's potential hardiness is reduced. Most references provide the recommended soil type for a particular plant. You will most commonly see "moderately fertile, well-drained loam" as the recommended soil condition.
Most Ohio soils are clay and may require amendments or special preparation before planting. Another option is selecting a plant that grows easily in heavy clay soil. The following plants grow well in heavy clay soil: northern bayberry, silver maple, catalpa, flowering quince, burning bush, forsythia, green ash, honey locust, privet, black locust and Oriental arborvitae.
Soil fertility and pH also affect plant selection and growth rate. Some plants require a regular application of fertilizer, while others survive quite well under low fertility. Likewise, particular trees and shrubs grow better in certain pH ranges. Rhododendrons, azaleas and fothergillas grow best in acidic (pH 5.5 to 6.2) soil.
Moisture availability also must be considered. Too much or too little moisture may be a limiting factor when choosing a plant. Few plants can tolerate constantly wet soil. When soil is saturated with water, air is forced out. Plants cannot move oxygen from the leaves to the roots. Oxygen must be absorbed through the roots. However, some plants are adapted to wetter soil conditions. Fact Sheet 1054, "Plants for Wet Areas" is Reference Woody.1.
Conversely, there are few plants that thrive in excessively dry conditions. Reference Woody.2, Fact Sheet 1055, "Plants for Dry Areas," provides a list. Water is essential for dissolving nutrients in the soil so they may be absorbed by the roots. Plants that grow well during summer droughts are becoming increasingly popular in areas where water shortages occur.
Irrigation is an option for some dry sites. However, it can be expensive and labor-intensive and must be applied on a regular basis. Planning a landscape with differing zones of watering needs is a practical approach. Place plants with similar moisture needs together to simplify irrigation and avoid incompatibility problems.
Exposure to sun and wind are important considerations in plant selection. Drying winds and reflected heat from buildings cause desiccation, especially during winter when the ground is frozen and moisture is unavailable to plants. Prolonged desiccation can result in death of individual cells and plant tissue. The leaves of broadleaf evergreens will curl to reduce the amount of leaf surface exposed to drying wind.
In summer, DROUGHT combined with high temperature and drying wind will cause noninfectious or environmental LEAF SCORCH on many plants. Leaf scorch can be intensified for trees that have roots growing under pavement. In this situation, moisture is blocked by the pavement. As the pavement heats, it raises the temperature of surrounding soil, causing it to lose more moisture.
The amount and intensity of sunlight influence plant growth and selection. Plants are often listed by sun and shade requirements. Placing a plant that requires a sunny exposure in a shaded environment may result in slow, leggy growth, reduced flowering and poor fall color. Conversely, plants that naturally grow in shade placed in a sunny exposure are likely to show symptoms of desiccation and leaf scorch.
There are various degrees of sun or shade. Full sun means 6 to 8 hours of exposure to sunlight. Filtered shade is sun coming through a canopy of leaves. Partial shade refers to an area that is shaded for part of the day and sunny for less than 6 hours a day. Deep shade is cast from a structure resulting in little or no direct sunlight.
Aesthetics is the subjective evaluation of beauty. Plants have individual and collective aesthetic value. Some plants are so beautiful, they can stand alone as a focal point. Others are individually less beautiful, but can be combined with complementing plants to create a pleasing effect.
Most landscapes are limited in the number of plants that can fit into the available space. Know the size of a plant at maturity and provide adequate space for it.
It is important to consider the aesthetic value of the plant throughout the seasons of the year. Too often, gardeners focus on the season of flowering and forget about the other seasonal qualities of a plant. Too many popular, spring-flowering plants have little else to qualify them for landscape use. Form, interesting bark, fall foliage and fruit are other important characteristics that can enhance the landscape throughout the year.
A plant that combines many of these characteristics throughout the year is called a four-season plant. Some flowering crabapples fall into this category. In spring, the flush of color from the blossoms is spectacular. The summer foliage is glossy and green. During autumn the small apples form, providing a second season of color. The best crabapple cultivars hold their fruit into winter adding aesthetic interest as well as food for birds.
With so many plants and so many design considerations, how does a gardener determine which plants to grow? You may choose to rely on the judgement of professionals. The Ohio Nurserymen's Association provides a list of preferred plants that are updated annually, Reference Woody.3. Dr. Michael Dirr's reference, THE MANUAL OF WOODY LANDSCAPE PLANTS, is indispensable.
The alert gardener observes what is growing in the neighborhood and evaluates the positive and negative aspects of these plants. At local botanical gardens and ARBORETA, you are able to see plants that are appropriate for your locality.
The shape and structure of the plant should blend well with the other plants and serve a purpose. Plants can be classified as rounded, oval, pyramidal, vase-shaped, upright, horizontal or columnar. Weeping trees, contorted shrubs and distinctive shapes will stand out from most landscape plants. These special forms should be used as focal points. Use contrasting form for added interest and depth.
[Illustrations from Landscape Gardening]
Too much contrast in form will result in a lack of harmony in your landscape. Plan for a plant's growth and mature form. Some plants change their form as they mature. The Scotch pine begins its life with a conical form, but matures into a windswept, irregular shape when mature.
Texture is frequently associated with foliage. However, the woody structure of a tree or shrub is also part of the texture. Fine texture is associated with small leaves and thin branches. Cotoneasters and willows are examples of finely textured plants. Coarse texture is achieved with larger leaves and thicker, sparse branches, as on oakleaf hydrangea.
Coarse textures are more appropriate for larger landscapes, while fine textures are more appropriate in a smaller landscape. A small area can be made to look larger by using finely textured plants. Coarsely textured plants should be used as accents in the smaller landscape.
Landscapes should have plants of different sizes for added interest. Taller plants normally form a backdrop for progressively shorter plants. The scale of the landscape and permanent structures must be considered when choosing plants. A towering tulip tree dwarfs a one-story home on a small lot.
The same tree is in scale with a three-story mansion on a large estate.
When planning a landscape, allow enough space for each plant to reach its maximum size. A mature Scotch pine tree has a spread of 30 to 40 feet and reaches a height of 30 to 60 feet. The small holiday tree that is only 5 feet tall and 4 feet wide should not be planted 8 feet from the corner of the house.
Many people crowd young plants together to make a new planting look good when it is planted. This is fine if some of the plants are removed as the most desirable plants grow. Alternatively, annuals or less expensive, short-lived plants can fill the gaps until the woody plants begin to fill the space.
Slow-growing plants are ideal for rock gardens or for a collection of dwarf plants. Slower growing plants require less maintenance. However, most people want woody ornamentals to grow as fast as possible. There are drawbacks to fast-growing trees and shrubs:
- They require more maintenance.
- Their wood is weaker than slower growing species.
- They are more likely to be damaged in high winds or during ice storms.
- They often have a shorter life span.
Plan the landscape so it is divided into zones of maintenance. These zones can be defined as the following:
- high care (frequent irrigation, weeding, pruning, edging, deadheading);
- moderate care (infrequent irrigation, minimal weeding because of mulching and pruning only for disease or damage);
- low care (no irrigation, naturalized plantings and only minor pruning).
Introduction | Botany | Soils and Fertilizers | Entomology and Pest Management | Plant Pathology | Plant Propagation | Houseplants | Lawns | Herbaceous Ornamentals | Woody Ornamentals | Vegetables | Herbs | Fruit | Glossary