Site Maintenance
By Dave Bloniarz, USDA Forest Service

Overview

The care of newly planted trees and other plants requires integrated efforts that range from inspection, corrective action and scheduled programming. Improper maintenance or neglect of an established tree or landscape may result in damage to property or people, while newly planted urban space represent an investment of time, expense and energy that can be lost through lack of proper care. In addition to losing the benefits of a well-established landscape, proper maintenance directly affects the safety, health, and welfare of its users.

Maintenance involves several categories of activities, including: monitoring, scheduling, pruning, insect and disease management, fertilizing and aerating, as well as removing dead or dying plants. Additionally, all of the hardscape elements, such as benches, lighting, signage, paving, fences, walls and other ‘built’ components of the landscape must be maintained in order for the landscape site to achieve its design intent, visual quality and ecological health.

Utilizing volunteers to assist in the maintenance of newly planted and established landscapes is often critical in order to make a project fiscally viable and sustainable in the urban landscape. Many of the same individuals, and organizations, which helped plant trees and build your hardscape features, are often willing to provide assistance in caring for a completed project. Keep this in mind as you plan for the upkeep and maintenance of your site. Support by the community is the main component of a safe, sustainable and well-maintained urban space. Training the community on various aspects of site maintenance will enhance the overall project, and ensure its success for decades to come.

Checklist for Maintenance of New Trees and Landscapes

Watering

Water plays many key roles in a tree's life. When water is in short supply, trees cannot function normally and will eventually die if the deficit is not corrected. The ground around the rootball of new trees should be kept moist for two years, generally the equivalent of one inch of rain per week, or at least 5 gallons of water per tree. Check soil moisture 2 inches below surface.

Newly planted trees possess only a small percentage of their original roots and must be closely monitored and watered carefully. Always check the moisture status of the soil around your tree before watering. A hand trowel or soil probe is a useful tool for performing this important investigation. If the soil is dry, water should be delivered at a slow rate using an oscillating sprinkler or soaker hose. Commercially available root feeding/watering probes can be used to deliver water directly into the rootball of recently planted B&B or container- grown nursery stock. Newly planted trees should be inspected at least once a week to determine if watering is necessary, and more often during hot, dry weather. Caution watering too frequently can also kill trees.

During extended periods of drought, large established trees also need to be watered. A single, large tree can transpire more than 100 gallons of water on a typical summer day. Before watering, check the soil moisture to a depth of 12 to 18 inches with a narrow spade or soil-sampling probe about midway between the trunk of the tree and the edge of the branch spread (dripline). If the soil is dry, water with a sprinkler or soaker hose to a depth of 18 inches. Water an area at least as wide as the branch spread. Well established trees often have extensive root systems that extend far beyond the tips of the branches and will benefit from water applied to the soil outside the branch spread. Root feeding/watering probes are useful tools for irrigating trees as long as they are not inserted into the soil deeper than 12 inches and are moved frequently. If possible, avoid applying chemically softened water to trees. Frequent use of softened water may harm soil structure and injure trees. The ground around the rootball of new trees should be kept moist for two years, generally the equivalent of one inch of rain per week, or at least 5 gallons of water per tree. Check soil moisture 2 inches below surface.

Mulching/Weeding:

Mulching involves the placement of wood chips, bark nuggets, pine needles, or other organic material over the soil surface surrounding a tree. The purpose of the mulch is to keep soil cool during the hottest months, reduce moisture loss from the soil, and eliminate weeds that compete with trees for water and nutrients. The zone of mulch can also help prevent injury to trees by keeping lawn mowers and weed trimmers away from the trunks of trees. Mulches should be applied to a depth of 2 to 4 inches and spread over as large a portion of the root zone of a tree as is possible.

The mulch should not be in contact with the trunk of the tree. Since organic mulches decompose over time, it will be necessary to replenish the mulch every few years. However, the depth of the undecomposed organic mulch should not exceed 4 inches. Maintain a wood or bark chip mulch ring approximately 4-ft. diameter and 2-4 inches deep, minimum, around each tree. Organic mulches will decompose and sometimes wash away, so make checks regularly and replacements when necessary. Replenish as needed, perhaps once per year. Pull weeds and grass from mulched area. For best results, continue to enlarge the mulched area in the future.

Pruning:

Trees respond in predictable ways to pruning. By studying these responses arborists have developed pruning practices that preserve or enhance the beauty, structure, and function of trees. The International Society of Arboriculture (ISA) has developed standards for pruning that provide general guidelines. Of course, each tree has a unique form and structure, so pruning needs may not always fit strict rules. However, it is the arborist that must take responsibility for special pruning practices that vary greatly from the standards.

The following pruning methods are recommended for mature trees:

Crown cleaning or cleaning out is the removal of dead, dying, diseased, crowded, weakly attached, and low vigor branches and watersprouts for the tree crown.

Crown thinning includes crown cleaning and the selective removal of branches to increase light penetration and air movement into the crown. Greater light and air movement stimulates and maintains interior foliage, which improves branch taper and strength. Thinning reduces the wind-sail effect of the crown and the weight of heavy limbs. Thinning the crown can emphasize the structural beauty of the trunk and branches, as well as improve the growth of plants beneath the tree by increasing the light penetration.

When thinning the crown of mature trees, no more than one-quarter of the foliage should be removed. At least one-half of the remaining foliage should grow from branches that originate in the lower two-thirds of the tree. Removing laterals from a branch requires a similar approach. Try to retain inner laterals and leave the same distribution of foliage along the branch. Trees and branches pruned in this way have stress more evenly distributed.

Removing the inside lateral branches also produces an effect known as "lion's-tailing." By removing all the inner foliage, weight is moved to the ends of the branches, which may cause the branch structure to weaken and limbs to break. Greater light penetration may cause sunburned branches and stimulate watersprouts.

Crown reduction decreases the height and spread of a tree. Thinning cuts will maintain the structural integrity and natural form of a tree, and delay the time when it will need to be pruned again. To make this type of cut, prune the branch back to its point of attachment or to a lateral that is at least one-half the diameter of the cut being made.

Crown restoration improves the structure and appearance of trees that have been topped or severely pruned using heading cuts. Select one to three main branch stubs that will grow to reform a more natural looking crown. Thinning or even heading may be required to match the weight of the new branches with the strength of their attachment. Restoration may require several prunings over a number of years.

Crown raising provides clearance for buildings, vehicles, pedestrians, and vistas by removing lower branches. It is important to maintain at least one-half of the tree's foliage on branches that originate in the lower two-thirds of the crown. This ensures a well-formed, tapered structure and uniformly distributed stress. When pruning for view, it's better to open "windows" through the foliage of the tree, rather than severely raising or reducing the crown.

Other notes to follow include: Remove all dead or broken branches at their source. Correct structural or form problems after trees become established -- approximately 3 years. Best time is mid-winter. Never remove the branch collar, or basal swelling of a branch.

Insects and Diseases:

Monitoring of your landscape will enable you to identify potential problems before they become major, and expensive, catastrophes. Watch for a build-up of leaf eating insects, which may cause brown, curled, or chewed leaves. Proper diagnosis of problem pests is important, and a program of plant health care, should be established for your landscape. During the growing season, one of the most common temptations to help a tree, shrub or grass is to spray a pesticide in order to 'get rid' of a bug or a disease problem. Alternative and effective insect and disease control may not require the use of chemical pesticides. A healthy, well-maintained tree is less likely to be susceptible to the effects of insects and disease, thus requiring intervention in only extreme cases. Again, careful monitoring of your landscape as part of an integrated plant health care program will prevent the need to apply expensive and potentially harmful chemicals.

In the extreme event that you might need to consider chemical applications, carefully consider the following Alternative Pest Control Strategies to control insect and disease outbreaks:

  • Biological, using organisms found in nature.
  • Use of insecticidal soaps or dormant oils to control insect pests.
  • Mechanical methods including water blasting.
  • Physical trapping such as 'tanglefoot' banding to prevent the migration of insects.
  • Pruning out diseased parts of a tree to control the spread of the disease.
  • Planting of 'pest resistant or tolerant' tree species.

Pesticides are toxic to humans, animals, pets and other beneficial organisms that share the same environment as the tree does. When the use of pesticides is required to control a serious pest problem, a licensed professional pesticide applicator should be consulted.

Fertilization:

Even in the most carefully designed landscapes, many trees grow in an extremely hostile environment, both above and below ground. The physical, chemical, and biological conditions of the soil may need to be managed just as elements of the trees' above-ground environment are managed. Fertilization and aeration are the primary methods of managing the area below the soil surface. Both are vital to the health and longevity of any landscape.

Trees need adequate amounts of nutrients, water and air in the soil. Without these elements trees will grow with less vigor and will be more susceptible to secondary problems, such as attack from insects and diseases. Properly nourished trees will be more able to withstand the attack of insects and diseases and tolerate the adverse growing environment afforded by most urban situations.

Fertilizers - Plants require at least sixteen chemical elements for proper growth and development. Three of these elements-carbon, hydrogen, and oxygen-are provided by air and water. The roots from soil obtain the other essential elements.

The specific fertilizers applied should be based on need. Every site is different; so soil tests should be conducted every two to three years. Your state Cooperative Extension Service can analyze samples of soil taken from each tree site and make specific recommendations.

Trees most commonly require large amounts of nitrogen. Because it is easily leached and often volatile, if necessary it may be necessary to apply nitrogen once or twice a year. Other chemical elements, such as calcium, phosphorous, potassium, and magnesium, seldom need to be added. Acidity and alkalinity are measured on a pH scale, with lower pH indicating greater acidity. Soil pH affects the availability of certain nutrients, particularly iron and manganese, so it's important to maintain the pH between 5.5 and 7.0 for most plants.

Growth rate and density of foliage may be improved by broadcasting 2 to 3 pounds of actual nitrogen per 1000 square feet, up to and just beyond the branch spread (Example: l/2 to 1 lb. 33-0-0 over a 10 x10 ft. square). Apply in late September to early November. May be applied in multiple applications. Begin second year after planting.

The following guidelines were taken from the National Arborist Association Standard for Fertilizing Shade and Ornamental Trees. Be sure to study the complete NAA standards before proceeding with a fertilizer program.

Generally, the ideal time of the year to fertilize is in the late summer or fall. Fertilizer can also be applied after leaves open fully until early July. Avoid treatment with readily available inorganic nitrogen in heavy doses between July and September, because it could cause a late flush of growth that would not harden off before freezing weather.

There are a variety of methods for fertilizing trees. Fertilizers can be broadcast over the surface of the ground, poured into holes drilled into the soil, injected as a liquid into the soil, sprayed onto the leaves, or injected directly into the trunk. Surface applications are most commonly used for fertilizers that contain only nitrogen. A properly calibrated, mechanical spreader broadcasts fertilizer over the ground in a pattern of concentric circles or linear strips beginning two or three feet from the trunk and extending five or ten feet beyond the drip line. Care should be taken to avoid excessive overlapping.

Drill holes allow relatively insoluble fertilizers, such as phosphorous, to be placed close to roots. Drill holes also provide valuable aeration in compacted soils. Arrange drill holes in concentric circles beginning about two to three feet from the tree trunk and extending five or ten feet beyond the drip line. Space the holes two to three feet apart. Drill eight to twelve inches deep, depending on the species of tree, pattern of root growth and type of soil. In compacted soil situations, it makes sense to drill deeper holes. Distribute the fertilizer uniformly among the holes after mixing it with peat moss, calcine clay, perlite, small crushed stone, sand or other appropriate soil amendment. If the area under the canopy is restricted, reduce the amount of fertilizer in proportion to the area fertilized or the number of holes drilled. Keep the fertilizer at least four inches below the surface. If shrubs live within the root area of the tree, take care not to drill holes closer than six inches to the crown of the shrubs.

Liquid injection also puts fertilizers into direct contact with tree roots. Drive the soil probe or lance eight to twelve inches into the soil. Make injections about two and one-half feet apart beginning about two to three feet from the tree trunk and working out to five or ten feet beyond the drip line.

Foliar spray cannot provide an adequate amount of all necessary minerals, however, spraying liquid fertilizer onto the foliage can correct minor deficiencies, especially iron. Micronutrient applications should be applied when first leaves reach full size. Within two to eight weeks, the tree should respond with greening foliage and normal bud growth on affected shoots. Species, age, time of year, soil conditions, and the severity of the deficiency will all affect the response time. One or two applications per year will generally control deficiencies, but under some conditions, maintaining healthy growth may require several treatments each year.

Aeration

- Pore spaces in the soil supply trees with air, as well as water. Some soils are naturally tight. Other soils may start out well aerated, but through the actions of pedestrians, vehicles, and even water, pore spaces are compressed. Soil compaction is far easier to prevent than it is to remedy. Preventive measures include limiting pedestrian and vehicular access, and mulching exposed soil to minimize compaction caused by the impact of rain or irrigation water.

If planting into a site with poor aeration, first rip or deep plow the soil, replace the soil with a suitable medium, or try to select trees tolerant of low soil aeration. Mechanical aeration is possible, but at best, it's a temporary solution. Physically separating soil particles merely buys time until the pore spaces cave in again. Physical aeration is similar to the sub-surface fertilizing methods mentioned previously. An auger or high pressure water probe breaks up soil particles that have been pressed tightly together. Surface penetrations should be eight to ten inches deep two to three feet apart and extend up to one-fourth of the radius beyond the drip line of the tree.

Tree Hazard Inspections:

Most tree hazards can be prevented by regular checkups and proper treatments by tree professionals. To determine the scope of work, a field survey should answer thirteen questions. These questions were taken from Dr. Alex Shigo's Tree Hazards: Your Trees Can Kill.

  • Target: If the tree falls will it hit cars, houses, power lines or people? If so, the need for immediate action becomes much greater.
  • Architecture: Has the tree grown beyond its normal form into a dangerous form?
  • History: Has the tree lost large branches recently?
  • Edge Tree: Were neighboring trees cut away recently leaving tall trees at the edge?
  • Dead Branches: Are there dead tops or branches? Is the tree dead?
  • Cracks: Are there deep, open cracks in the trunk and branches? Cracks are major starting points for trunk and branch failures. Crack drying is just as important a factor leading to failures as over loading and decaying wood.
  • Crotch Cracks: Are there deep, open cracks below joining stems?
  • Living Branches: Do living branches bend abruptly upward or downward where tips of large branches were cut off?  Living branches may pull out of trunks that are weakened by rot or cracks. Long periods of hot, dry weather may dry out the rot or cracks and weaken the union of the branch on the trunk. Beware of large branches on rotten or cracked trunks.
  • Topping: Are large branches growing rapidly from topping cuts on big trees? Sprouts that lean away from topping cuts have weak attachments. Sprouts near the edge of a cut may roll inward as it grows and further weaken the attachment.
  • Storm Injury: Are there broken branches, split trunks, or injured roots?  Are branches close to power lines?
  • Root Rot: Are there fungus fruit bodies (mushrooms) on roots?  Were roots injured by construction?
  • Rots and Cankers: Are there hollows or cankers (dead spots), some with fungus fruit bodies? Is the tree leaning?
Tree Maintenance Timetable
Years After Planting Necessary Desirable Optional
0 - 3 Watering Mulching/Weeding Pest Management Stakes & Guards
3-5 Mulching/Weeding Pruning Watering Plant Health Care Stakes & Guards Fertilization
5-10 Pruning Mulching Plant Health Care Fertilization
10 and Beyond   Pruning Fertilization Mulching Plant Health Care

Sources (users of older browsers may need to copy and paste address/location links to open sites)

The materials contained in this abstract were adapted from the following publications:

“Organizing and Managing Nonprofits.”   2002. Tree Link. Internet resource document/site. Available online at http://www.treelink.org/.

Volunteer Today: The Electronic Gazette for Volunteerism.”  2002. By Nancy Macduff. Internet resource document/site. Available online at http://www.volunteertoday.com/internet.html.

“Portal to Internet Sites for Volunteer Requirement, Management and Training.”  2002. Developed by Volunteer Today. Nancy Macduff. Internet resource document/site. Available online at http://www.volunteertoday.com/internet.html

“Horticulture and Home Pest News”  1997. Jeff Iles, Iowa State University. Internet resource document/site. Available online at http://www.ent.iastate.edu/ipm/hortnews/1994/8-12-1994/hohtree.html

“Tree Maintenance - When is it necessary?”  2002. City of Winnipeg, Public Works Department - Parks and Open Space Division. Internet resource document/site. Available online at http://www.city.winnipeg.mb.ca/PWDforestry/index1.html.

“Tree Maintenance.”  2002. Missouri Department of Conservation, Missouri Conservation Commission. Internet resource document/site. Available online at http://www.conservation.state.mo.us/forest/urban/
UrbanAndCommunityForestry/treemaintance/.

“A Technical Guide to Urban and Community Forestry.”  USDA Forest Service. Available online at http://www.na.fs.fed.us/spfo/pubs/uf/techguide/maint.htm.

“Landscape Maintenance Practices Save Water.”  2002. Texas Agricultural Extension Service. Internet resource document/site. Available online at http://aggie-horticulture.tamu.edu/plantanswers/drought/drought3.html.

New Tree Planting. 1995. Informational brochure produced by the International Society of Arboriculture, P.O. Box 3129, Champaign, IL 61826-3129. Available online at http://www2.champaign.isa-arbor.com/consumer/planting.html.