Urban Tree Care

Homeowners and community staff can use these tree care tips to plant and maintain trees. Trees require sunlight, sufficient water, moderate temperatures, well drained soils and adequate nutrients to become established.

Construction

Urban Tree CareRoots of mature trees extend far beyond the extent of the branch tips (drip line). With adequate soil, tree roots may extend as far as 2 1/2 times the diameter of the drip line. The majority of nutrient absorbing roots exist in the upper 12 to 16 inches of soil.

During construction, tree conservation efforts require that a large portion of the tree's root system, the critical root zone (CRZ), be protected for all trees to survive. Consider removing trees that have sustained CRZ loss in excess of 30%. Tree species, health, structure, soil type, vegetation competition, proximity to structures, future planned impacts, and planned maintenance all contribute to the determination of which trees should be removed and how remaining trees can be protected.

Trees may not die immediately, but could decline over several years. With this delay in symptom development, you may not associate the loss of the tree with construction.

How to Conserve Natural Resources on Construction Sites (publication)

Drought

Water is the single most limiting essential resource for tree survival and growth. Drought conditions can severely affect young and old trees alike leading to tree decline, pest problems, and non-recoverable damage as well as decreased rates of diameter and height growth. More than eighty percent of the variation in tree growth is because of water supply.{1} Although providing adequate water to newly planted trees is essential, replacing older, more valuable trees lost or damaged due to lack of water can be especially difficult since they can take decades to grow to the same size. With the many social, economic and environmental benefits that trees provide, it is important to continue caring for our trees even in times of drought and tightening water restrictions.

The signs of drought stress can be observed mostly in the foliage of trees. Symptoms such as leaf drop and curling, wilting, or discolored leaves as well as dead branches are all signs of dry roots. Many people may not realize that their mature trees are stressed since these symptoms first appear in the top center portion of the canopy which may be far from view.{2} However, it is better to apply water preventatively before these symptoms even appear.

Considering that state and local watering restrictions may be in place, here are some tips to help weather the dry conditions:

Tips for Watering Trees During a Drought

  1. Mulch trees. (Add mulch at a depth of three inches. Place it over the tree roots. Do not place mulch against the tree trunk.)
  2. Use recycled water or gray water from your home (dehumidifier, air conditioning condensate, or shower before it heats.)
  3. Pump water from other sources such as detention ponds, lakes, creeks or cisterns. Remember to get permission from the landowners if the water source is not on your property.
  4. Use gator bags and refill them with recycled water.
  5. Ask the fire department to use water that is recycled from their trucks. Follow crews as the fire hydrants are drained and collect the water. A large tank is needed to collect water as it is under high pressure.
  6. Get a permit (contact your local county government) and pay to bring water in from other sources. Your trees provide more benefits than this cost.
  7. When you are able to provide water, the most beneficial time to irrigate plants is during the late night and early morning hours. Evaporation is minimized, and the foliage has time to dry out during daylight hours. Evening watering is efficient for water use, but should be applied after dew is on the leaf surfaces
  8. Install a rain barrel at your planting site.

What Not to do during drought conditions:

  • Do not prune live branches which forces the tree to expend energy to heal the wound from the cut. Removing live foliage also reduces the capacity of the tree to grow once rains return.
  • Do not fertilize trees in extended drought since this pulls water from the roots and forces the tree to expend precious energy to process the fertilizer.
  • Do not dig under the canopy of a tree during drought because this will reduce the capacity of the tree to uptake water{2}.

Additional tips on watering trees

{1} Coder, Kim D. 1999

{2} Gilman, Edward F. 2007

Insects and Diseases

Insect pests and diseases often attack trees which are already under stress or weakened. Drought, improper planting and disturbance of the root system through digging, trenching, construction activity or addition of soil to the root area can make trees more susceptible to attack. First, find out why the tree is weak and then treat the primary cause of the stress.

Examine your tree regularly, looking for anything out of the ordinary: sap coming out of the bark, smaller leaves that are less green than usual, leaf spots, branch die-back in the canopy or leaves changing color early. Mushrooms at the base of a tree can sometimes indicate root rot and may warrant removal. Consult a Certified Arborist.

Always identify the pest or disease before applying sprays to control it. Some tree pests do not require control measures and some diseases have no practical control. A fungicide will never control an insect problem. If you cannot diagnose a problem, get professional assistance from a local nurseryman, professional arborist, or state forestry agency.

Mulching Trees

Mulch is a material placed over the soil surface of the trees’ root zone to maintain moisture and improve soil conditions. Mulching is one of the most beneficial things that can be done for the health and growth of a tree. A thin layer of mulch (2-4 inches deep) can improve soil structure, oxygen levels, temperature, and moisture availability.

Recommended Mulch Materials

Good quality mulch materials are usually readily available. Organic materials are preferable over inorganic materials (rock, stone, shredded rubber). When organic mulching materials decompose, they must be replenished.

  • Wood chips, composted for 4 months minimum
  • Pine needles
  • Tree bark
  • Leaf mold
  • Compost

When to Mulch

  • Annually, in spring, before soil moisture decreases and temperatures increase
  • Prior to, during, and after construction or infrastructure changes affecting tree roots and tree health
  • After tree injury

How to Mulch

  • Apply mulch in a circle covering the entire root system of a tree. Most of the fine, absorbing roots of a tree extend well beyond the tree canopy, or drip line.
  • Mulching with a deep layer can be harmful! The general recommended mulching depth is 2-4 inches.
  • Mulch piled high against the trunks of young trees may lead to insect and disease problems. Keep mulch at least 6 inches from the base of the tree trunk.

Benefits of Mulch

  • Conservation of soil moisture
  • Improvement of soil structure
  • Reduction in soil compaction
  • Increase in soil aeration
  • Increase in nutrient availability
  • Suppression of grasses and weeds
  • Aesthetically pleasing
  • Helps prevent damage from mowers and weed whackers

Nursery Stock - Tree Selection

The successful growth of a tree to maturity depends on the quality of the tree itself.

Do not choose a tree that has:

  • Had the central leader cut back (topped).
  • Damaged back or old wounds on the trunk or branches.
  • Been pot bound by a container, or has girdling roots. Remove the container and inspect the root system.
  • Been planted too deep in the container (trunk root flare should be obvious).
  • Too small a root ball for the diameter of the trunk. Root ball diameter should be 10 to 12 inches for every inch of trunk diameter measured at 6 inches above the soil.
  • Broken branches, diseased or discolored leaves or cracked bark.
  • Been marked down in price (seems like a bargain). Don't expect it to do well even if it is properly planted and maintained.

Do plant and maintain a tree that:

  • Meets the American Standards for Nursery Stock (ANSI) for landscape trees.
  • Is the correct species for the selected planting site.

Planting - Basic Installation

  1. The tree planting area should be tilled to a depth of 6 to 8 inches (deeper if the soil is compacted) for an area 10 times the diameter of the root ball.
  2. Dig a hole 3 times the diameter of the root ball and no deeper than the ball or the container. Leave the soil at the base of the hole compacted.
  3. Remove the container, cut girdling roots and place the tree in the hole. For Ball and Burlap trees, remove all ties, strapping, wire basket and burlap. The top of the root ball should rest no more than one inch above the existing soil line for every 10 inches of root ball depth and never lower than the existing soil line. (A 15 inch deep root ball should rest 1.5 inches above the existing soil line.)
  4. Backfill the hole with the un-compacted, previously removed soil. Lightly pack the soil and water the trees as you go to eliminate any air pockets. Build a mound of soil or mulch in the ring at the outer edge of the planting hole. See mulch.
  5. Stake the tree if wind throw is a significant issue and allow for 3 inches slack in the tie wires. Never allow bare wires to contact bark. Remove stakes and all wires, hoses and ties after the first growing season.

Pruning Young and Mature Trees

Pruning controls the appearance, shape and growth patterns of the tree and keeps branches from harming structures or people. Improper pruning can cause damage that will last for the life of the tree, or worse, shorten the tree’s life.

Pruning Young Trees

What to Prune

  • Only remove dead, dying, diseased, broken or crossing branches.
  • Remove branches when there are conflicts with utility lines (always consult a professional) and lines of sight related to pedestrian and vehicular traffic, and low limbs over sidewalks.
  • If young trees are forked at a narrow angle, prune to create one central leader. This trains the tree to grow straight.
  • Remove sprouts or suckers at the base of the tree or inside the tree crown that are upright and grow rapidly.
  • Pruning should be done sparingly. If you remove too many leaves, a tree cannot gather and process enough sunlight to make food.

When to Prune

  • For most trees, prune in late winter or early spring before leaves emerge.
  • Prune dead, diseased and broken limbs as soon as you notice them. Prompt pruning prevents the spread of decay and cavity development.
  • Young trees should not be pruned for shape until after the first two growing seasons.
  • Never remove more that 25% of the live crown (leaves, twigs and branches) in a single year.

How to Prune

  • When pruning diseased branches, dip the pruners in household bleach or rubbing alcohol before storing or making the next cut.
  • Once you begin a cut, always finish it.
  • Trees do NOT need wound dressings to recover from pruning. Through natural processes, the tree will callus over the wound by itself.
  • Pruning mature or large trees should be left to Certified Arborists. Large branches are removed by making three cuts.
  • Consult the International Society of Arboriculture for more information.

Pruning Mature Trees

Pruning mature trees may require special equipment, training and experience. If the pruning work requires climbing, the use of a chain or hand saws, or the removal of large limbs, the use of personal safety equipment, such as protective eye wear and hearing protection is a must. Certified Arborists can provide a variety of services to assist in performing the job safely and reducing risk of personal injury and damage to your property. Trained crews will have all of the required safety equipment and liability insurance. They are also able to determine what type of pruning is necessary to maintain or improve the health, appearance and safety of your trees.

Avoid using the services of a company that:

  • Advertises tree topping as a service. Topping is harmful to trees and is not an accepted practice.
  • Uses tree climbing spikes to climb trees that are being pruned. Climbing spikes can damage trees, and their use should be limited to trees that are being removed. If branches have broken, stubs remaining on the tree should be pruned back to the next largest branch.

Correct Steps to Pruning

  • Step A – Cut through ½ of the branch from underneath about 1 foot from the trunk. This will help prevent stripping or peeling the bark off of the trunk.
  • Step B – A few inches further from the first cut, make a cut from the top of the branch downward. This will remove the entire branch.
  • Step C – Locate the branch collar (a layer of wrinkled bark where the branch attaches to the trunk) and where the branch bark ridge (a raised area of bark at the branch/trunk union). Make the final cut just outside of the branch collar and the branch bark ridge, at a slight downward and outward angle. Do not cut into the collar or leave a stub.
Pruning Trees

Topping

Topping is a harmful pruning practice in which tree branches are cut back to stubs. Topping trees will make them more hazardous in the long term. Proper pruning methods exist to reduce tree height versus topping, which can cause decay of the branches and attract insects and disease.

Watering

Water is the single most limiting essential resource for tree survival and growth. Drought conditions can severely affect young and old trees alike leading to tree decline, pest problems, and non-recoverable damage as well as decreased rates of diameter and height growth. More than eighty percent of the variation in tree growth is because of water supply.{1} Although providing adequate water to newly planted trees is essential, replacing older, more valuable trees lost or damaged due to lack of water can be especially difficult since they can take decades to grow to the same size. With the many social, economic and environmental benefits that trees provide it is important to continue caring for our trees even in times of drought and tightening water restrictions.

Newly planted trees should be regularly watered for the first three years. Water newly planted trees every few days initially, then once a week depending on soil conditions and rainfall. Weekly to monthly watering should continue until the tree is established in the landscape.

Established, mature trees should be watered every 2 to 4 weeks during drought conditions by thoroughly wetting the top 12 inches of soil under the tree’s canopy. This may takes several hours or more depending on what type of application devices are available to you. If you have limited time to devote to your trees, it is better to completely wet a small area than to only wet the surface few inches over a large area. Limit pedestrian, mower and vehicle traffic under the tree. {2}

A good slow soaking over several hours is the most efficient way to water trees. Using a soaker hose, drip irrigation, a Tree gator watering bag, or slow drip bucket which applies water at ground level is the best way to accomplish this and to avoid water loss due to evaporation or runoff. This method also focuses the water over the root area and keeps the leaves and trunk dry which can prevent opportunities for harmful pests and diseases. Don’t over water. Too much water can kill a tree by eliminating the air from the soil and suffocating the roots. The soil should not stay saturated, but have time to dry out between waterings.

As a general rule, 2 gallons of water should be applied for every 1” of tree diameter.

{1} Coder, Kim D. 1999

{2} Gilman, Edward F. 2007

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