2.1 COST AND MAINTENANCE

An important consideration when selecting plant material is maintenance. Time and money are spent maintaining our landscapes, and everyone welcomes a chance to reduce these costs. With proper planning, landscapes can be designed to increase efficiency in watering and maintenance. The location, size, and design of planting beds can aid in reducing evaporation and runoff, as well as yielding healthier plants requiring less maintenance and care. Using two to three inches of mulch, such as shredded bark, pecan hulls, or compost keeps the soil temperature cooler and reduces weed competition.

Bare areas in the landscape (under trees) must be covered with groundcover, grass, or mulch to reduce erosion. All plants need sunlight to grow. In areas shaded by trees, the removal of a few branches allows more sunlight to penetrate through the canopy for understory plants. One should select understory plants that have similar moisture requirements as the established tree to avoid overwatering the tree. For example, fescue grass requires up to two inches of water each week during the growing season. For many established trees, this may be too much water and may cause the tree’s health to decline.

Choosing trees adapted to our climate and soil conditions will reduce time and resources spent on landscape maintenance. Non-native trees may not be adapted to our soil conditions or our extreme moisture and temperature variations. Struggling with these conditions weakens their defense mechanisms and increases susceptibility to pest attack. The proper selection and site location of trees can reduce the costly replacement of sick or dead plants.

2.2 COMMON PROBLEMS OF TREES

• Wet feet - Over watering and clay soils are the main contributors to this condition. Some trees do not tolerate clay soils, which contribute to poor drainage. Often, trees respond to wet feet by wilting, and may be mistakenly interpreted as lack of water.



• Nutrient deficiency - Soil pH affects the availability of nutrients that trees and plants can absorb. If the pH is too high or low, the plant may not be able to utilize nutrients even though they are sufficient in the soil. A soil test clarifies this situation and an expert can recommend proper treatment.



• Leaf/trunk damage - Some trees are sensitive to the hot, drying summer winds common to Oklahoma. Often, the tips of leaves turn brown in the summer due to this condition. Although trees can toleratesummer leaf damage, sunscald injury that occurs on tree trunks is more difficult to overcome. This occurs on warm winter days when the temperature of the bark rises and then drops quickly. To reduce this damage on young, thin-barked trees, place tree wrap on the trunk during winter months, or retain leaves and small branches about the trunk.



• Diseases - Disease organisms that infect trees include fungi, bacteria, viruses, and nematodes. Symptoms caused by these organisms include leaf spot, stem die-back, cankers, root rot, and wilts which can lead to the death of the tree, depending on the organism or the severity of symptoms. Favorable conditions that promote organism infections and growth include consistent low light or cloudy days, leaf wetness and/or high humidity for several hours, and mild temperatures. Removal of diseased leaves, needles, and trees reduces the spread of disease. Before applying any chemicals, consult an expert to determine if a fungicide is necessary or available. The best method for reducing the occurrence of disease is to select and plant disease-resistant trees.



• Insect problems - Pest insects are attracted to stressed trees. Most insects harm trees by feeding on leaves, which may lead to defoliation. As the tree uses precious energy to produce new leaves, the health of the tree may continue to decline. A few insects are vectors that transmit devastating disease organisms. If insect populations are high and severe damage is anticipated, a high-pressure water hose will knock many from leaves. Consult an expert to determine if an insecticide is necessary before applying any pesticide.



• Ice/Wind - Strong winds and heavy accumulations of ice or snow may break weak-limbed trees, or cause trees to uproot. Select slow growing trees that tolerate these weather conditions. For example, Silverleaf maples grow fast and are notorious for receiving wind damage. Consult a professional tree trimmer to properly prune trees to prevent an accident or further tree damage. ALWAYS consult an expert before pruning trees with storm damage. Some trees may require removal instead of selective pruning.



• pH problems - Most soils in Central Oklahoma have a high pH (alkaline). Some plants will not tolerant alkaline soils. To ensure the vitality and long-term health of your plants, select trees that tolerate high pH soils. If pH problems are suspected to be affecting established trees, an expert can interpret a soil test result and recommend the proper amount of sulfur to reduce the pH level.³

2.3 MOWING

The type of turfgrass can increase or greatly reduce time and money spent maintaining a manicured lawn. A benefit of using native turfgrass is the significant reduction in the number of times mowing and trimming equipment must be used. Allow all grasses to grow to their recommended height for optimal root growth. As roots grow deeper, grasses are able to access more ground water, in turn enabling them to better withstand drought conditions. Less supplemental irrigation is then required. Some grasses, such as Bermuda, have a tendency to overtake other plants and weaker grasses (weeds). This is a desirable characteristic in turf areas, but can be a serious problem in planting beds and walkways.

2.4 CHEMICAL APPLICATIONS

Water pollution is caused by careless or ignorant use of chemicals. Oftentimes, homeowners do not follow label directions, and use chemicals in greater quantity or more often than is recommended. Furthermore, proper disposal techniques often are disregarded, and unused pesticides and other chemicals are discarded in household or storm drains. This activity contaminates our surface and ground water.

Fertilizers are a source of pollution in urban areas. Too often, fertilizer is applied without a nutrient analysis of the soil. Unused nutrients lead to groundwater contamination through leaching and surface water pollution through runoff. The largest concern with polluted groundwater is that many individuals, cities and towns rely on groundwater as their sole water supply, and must contend with these pollutants in their drinking water. Surface water is negatively affected when algae and other aquatic weeds grow due to increased phosphorous and nitrogen levels. As these weeds grow on the surface of the water, they affect the health of aquatic life as they limit light penetration and deplete oxygen production. In turn, this greatly affects the health and quality of surface water. Applying the correct amount of fertilizer to the soil and reducing polluted runoff into surface water will help prevent this devastation to aquatic wildlife.

Pesticides are another source of chemical pollution. Often pesticides are used in response to a disease or insect problem. Less than 10% of the insect population is actually harmful to plants, yet insecticides eliminate many more insects - including beneficial ones.⁴ When insecticides are used and the beneficial insects are killed, the pest insect problem may become worse in the next generation without a “check and balance” system in place. For many small insects like aphids or lacebugs, predator insects keep pest insect populations balanced. Many trees tolerate pest damage without detrimental affects; therefore, pesticides are not always necessary. Pesticides are important tools that should be respected and used according to label directions.

Reduction of unnecessary fertilizer and pesticide application is simple. First, correctly identify the plant problem(s). Non-experts assume insects and diseases cause most plant problems. Actually, most plant problems are related to health problems caused by environmental stresses. Practices that influence plant health include planting the tree in the right site, providing proper irrigation, selective pruning, fertilizer application following recommendations made from a soil test result, etc. An expert can correctly identify the plant problem and recommend a solution.

2.5 IRRIGATION

Many landscapes require supplemental water through irrigation systems. However, irrigation systems are often inefficient and contribute to over-watering and runoff. When designed and installed correctly, irrigation systems are efficient tools. Proper system zoning and careful placement of sprinkler heads that avoid over-spray onto impermeable surfaces can reduce runoff. This runoff, which often contains pollutants from fertilizer or pesticide, enters storm drains and is not treated when it empties into the nearest creek, river, or lake. Drip irrigation is a more efficient alternative to an underground spray irrigation system. Drip lines waste less water from evaporation, and are less expensive. Watering in the morning versus in the heat of the day further reduces waste from evaporation. Finally, plant selection that does not require supplemental watering eliminates the necessity for irrigation systems all together.⁵

Irrigation systems affect the health and development of plants. It is important to know the water requirements of trees and other plant materials, and use them in conjunction with plants that share the same requirements. Irrigation timers are often set to water for a short period of time on a regular basis. The key to irrigating established plants is to watch for signs of wilting, and then water as needed. Thorough, infrequent watering will establish deep, well-rooted plants that are more water-efficient (refer to Section 5.12 for watering practices.)

There are situations where supplemental irrigation is needed. During the establishment period for trees, frequent watering is required to allow the root system to develop. This establishment period may take up to two years. Past this point, watering during times of drought, or at the first signs of wilting, should suffice to maintain a healthy tree.

Irrigation during drought periods is essential to maintain plant health. Winter desiccation due to lack of moisture is very common in Oklahoma. Plants need moisture throughout the winter, and should be watered every few weeks if no natural moisture occurs. This is the same recommendation for summer droughts to reduce summer stress. Trees recharge during the night, and if soil moisture is not available to all of the root system responsible for water uptake, the tree begins to function in a deficit situation, resulting in the loss of leaves. Some plants may go into a short dormancy period until cooler temperatures and rainfall occurs. Other plants simply die.

Finally, over-watering can be just as detrimental to trees as under-watering. Certain trees are sensitive to the amount of water held around their roots. Many cannot tolerate what is known as “wet feet.” Most plants prefer to be well watered with a period in between waterings to dry out.

Natural wet/dry cycles are beneficial to plant health for several reasons:

1.  Spaces for air form in soils as they dry, providing oxygen to the plant. Constant moisture in the    
    soil, like that which is produced by the over-use of automatic irrigation systems, may reduce soil   
    aeration.

2.  Proper soil aeration stimulates root activity, which directly relates to the production of healthy  
    foliage. Waterlogged soils restrict root functions in most plants, leading to low energy levels    
    and less foliage growth.

3.  Soil retains strength and firmness from drying periods, allowing it to retain its structure. Moist 
    or wet soils compact more easily than moderate or dry soils. Over time, this constant compaction  
    (even from foot traffic) will destroy air pockets in the soil, suffocating the roots.

4.  Constant moisture in the soil causes environmental conditions conducive to disease-producing 
    organisms.

5.  Lastly, moderate moisture stress causes the plant to rapidly build energy reserves instead of 
    expending the energy toward new growth. This reserve is then triggered by a natural wet cycle and 
    produces an abundance of healthy foliage and blooms.6

2.6 XERISCAPING – A WATER CONSERVING PRACTICE

Xeriscaping is a practice of planning gardens around tight water budgets. Often mistaken for gardens of rocks, sand, and cactus, xeriscape gardens are as diverse as the native plant palette of a region. Water conservation through xeriscaping is accomplished by implementing the following seven principles:

1. Planning and Design

2. Soil Analysis

3. Practical Turf Areas

4. Appropriate Plant Selection

5. Efficient Irrigation

6. Use of Mulches

7. Appropriate Maintenance ⁷

Other maintenance practices that save money, time, and natural resources are as easy as the application of a thick layer of mulch to planting areas as necessary. Mulched soils retain moisture, limit evaporation, regulate soil temperature, reduce erosion, and prevent the establishment of weed seeds. Together, all of these practices will decrease time spent maintaining the landscape, preserve natural resources, and help protect the environment.

2.7 CONSERVATION OF NATURAL RESOURCES

Our most precious natural resource is water. Water conservation is becoming a crucial factor in planning for future growth as our population increases and the demand for water soars. Moreover, the quality of water is vital for future prosperity. As water becomes in greater demand, our society will have to adopt new practices toward the irrigation of landscaping to help conserve water for more important uses. During times of drought, water rationing may be implemented, adversely affecting plant health. Supplemental watering and irrigation systems may be reduced or eliminated by planting drought-tolerant species in the landscape. These plants, once established, maintain a balance that survives normal droughts.

Over-watering can also affect the availability of nutrients in the soil. Excessive watering may leech nutrients into sub-soils, where the roots cannot reach, requiring the application of additional chemical fertilizers. As the same watering practice is continued, these chemicals migrate into groundwater supplies, or are washed away in runoff. Fertilizers and herbicides that leech into the water supply are carried by runoff into streams and lakes, affecting water quality and causing toxins to accumulate in the environment. Pollutants in the water supply, adversely affecting the health of plants and animals, impact bio-diversity within the environment. ⁸

Many factors are attributed to runoff in urban areas. Inefficient sprinkler systems, expanses of impermeable surfaces, improper grading, and inadequate groundcover or vegetation all contribute to runoff in the urban environment. All of these factors may be amended with careful consideration of landscape design and selection of appropriate plant material.

In time, our society may be induced to begin a tradition of using more native landscaping, especially if landscape professionals take the lead and use Oklahoma tolerant plants effectively in their urban designs. If we emphasize through education and example the beauty of these plants, along with the benefit of protecting our environment, homeowners may eventually compete to have the most natural-looking landscaping on the block.

2.8 TREES IN THE URBAN ENVIRONMENT

Trees provide many benefits to the urban environment by providing:

• shade that helps cool the environment by reducing radiated heat from paved surfaces;
• increased humidity through respiration;
• habitat for wildlife; and,
• pleasing aesthetics to surroundings.

Unfortunately, harsh conditions in urban settings often limit our choice of trees species. We must carefully select trees that are adapted to the stresses of the urban environment, which include some or all of the following:

• Limited water availability
• Excessive salts
• Restricted root zones
• Soil compaction
• High soil alkalinity due to leaching from cement
• Low soil fertility
• Poor soil structure
• Pollution from fertilizers and pesticides
• Vandalism
• High winds created by clusters of tall buildings
• Radiated heat and light
• General disturbances and stresses from humans

Measures to ensure the success of trees in the urban setting are:

1.  Plan for tree growth and maintenance in the design of all building projects;

2.  Provide adequate space and quality of soils in root zones of street and parking lot trees. This    
    will improve tree growth, and reduce maintenance and irrigation (refer to Section 5.6 for tree  
    spacing recommendations);

3.  Provide adequate water to a tree during its establishment period (refer to Section 5.12 for 
    watering recommendations); and

4.  Select tree species or cultivars that are tolerant of stressful conditions and are appropriate for 
    their location.9