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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

February 1996

The forest where we live

Caring for trees in towns and cities

Did you know that 80 percent of Wisconsin's people live in the forest – the urban forest? Don't let the word "urban" fool you: Communities of all sizes, from Milwaukee to Minong, are part of this vast leafy network.

If you took a look at your community from the air you'd see a network of green between the streets and buildings. The urban forest is all of the trees and other vegetation in and around a town, village or city. It includes trees along streets, in yards, school grounds, parks, riverbanks, cemeteries, vacant lots, utility rights-of-way, adjacent woodlands and anywhere else trees can grow. Shrubs, flowers, vines, ground covers, grasses and a variety of wild plants, animals and microorganisms also are part of the urban forest. Streets, sidewalks, buildings, utilities, soil, topography, climate and, most importantly, people are all part of the urban forest ecosystem.

Benefits of the urban forest

Trees provide more than just beauty to your community. They release oxygen we need to breathe. They absorb and trap carbon dioxide and other pollutants. A large tree canopy softens the blow from a downpour, allowing rain to soak gradually into the ground. Less runoff reduces flooding, pollution, sedimentation in rivers and lakes, and the need to build bigger storm sewer systems. Increased soil moisture helps recharge local aquifers. Trees and green space change sunlight into stored energy instead of heat; they bring water up from the soil through transpiration and cool hot cities through evaporation. Trees properly placed around buildings provide shade in summer and insulation in winter, reducing air conditioning bills up to 25 percent and heating bills by 10 to 20 percent. The less energy we use, the more we can reduce pollution from burning fossil fuels.

Trees contribute to a sense of community. They muffle noise and provide places to rest, meet and socialize. Studies have shown that treed landscapes evoke a "relaxation response" in people. Patients recovering from surgery in a room with a view of trees required fewer strong pain relievers, experienced fewer complications and were released from the hospital sooner than those without such a view. Recent research indicates that trees reduce the incidence of violent behavior in nearby residents.

Trees increase property values by 5 to 20 percent. People linger and shop longer along tree-lined streets. Apartments and offices in wooded areas rent more quickly, have higher and longer occupancy rates. Businesses leasing office space in wooded developments find their workers are more productive and absenteeism is reduced.

Caring for the urban forest

Trees in the urban forest have been taken out of their native habitat and need care to maintain their health, vigor and safety. Restricted growing space, compacted soil, air pollution, dog urine, bicycle locks, lawn mowers, string trimmers, vandals, car bumpers, road salt, weed killers, storms, diseases and insects make life difficult for urban trees. Small wonder that downtown trees live an average of only eight years and suburban trees live only 30 years, compared to over 100 years for many trees in their native habitat.

In the woods, a tree with a dead limb isn't a problem, but in your neighborhood a dead limb is a hazard. It could fall on your house, garage, car or worst of all, on a member of your family. Branches that hide traffic signs can lead to accidents. Trees that grow into power lines can cause power outages in storms.

A community forestry program, whether run by local government, a volunteer tree board or even a private property owner, provides the management an urban forest needs. An inventory and management plan guide the selection of tree species to be planted, and outline regular maintenance, including pruning, removing hazardous branches and tracking disease and insect outbreaks.

In communities, trees face an even more deadly foe – budget cuts! Because trees, parks and green space are mistakenly thought to take care of themselves, they are the first to feel the budget ax. Policy makers must understand that trees provide more than just beauty. They are an integral part of a community's infrastructure. With proper care our "green-frastructure" can increase in value and contribute to our quality of life.

What you can do

The following information will help you care for your own trees, but remember, the urban forest doesn't stop at the end of your lawn. Get involved in your community's urban forestry program. If it doesn't have one, you'll learn here how to get one started.

Each of us living in a community has a part to play in our environment. The urban forest forms a web that joins us all; caring for it will sustain our lives and our communities.

The sum of its parts

A tree survives through the intricate relationships of leaves to roots, branches to bark, water to air, and people to plants.

Trees live longer, grow taller, and have greater mass than any other living organism. To sustain the health and longevity of these beautiful, complex plants in an urban landscape, humans need a basic understanding of how trees function.

Energy and growth

Trees need sunlight to power photosynthesis, the fuel-making system for green plants. To get first crack at the sun, trees keep their "solar panels" (leaves) above the competition by growing ever taller and wider. Leaves use energy from the sun, carbon dioxide from the air, and water from the soil to manufacture sugar, the basic fuel for plants, humans and animals. During this process, leaves also release oxygen into the atmosphere. The sugar is converted into wood, cellulose, and bark, or combined with nitrogen and other elements to make starches, fats, oils, and proteins to form fruits and seeds.

Trees grow in both height and diameter. Trees grow taller and branches grow longer due to cell division at the branch tips. Trees gain girth from cell divisions in the cambium, a single layer of cells between the bark and the wood. Each year as the cambium cells divide, new layers of wood and inner bark are inserted between the previous year's layer of wood and bark. The cambium produces wood (xylem) cells to the inside, and bark (phloem) cells to the outside.

Roots

Tree root systems consist of large woody roots and smaller, short-lived feeder roots. Although many of the small roots die off shortly after they are formed, the majority of these roots die in winter and are replenished in early spring. Tiny water-absorbing root hairs form on the surface of the feeder roots. Root hairs are very short-lived and are continuously replenished during the growing season. Roots grow in length, and the large woody roots, which contain a cambium layer, also grow in diameter.

Roots grow much closer to the soil surface than is commonly believed. Although a few roots may be found in the subsoil, most roots, especially the important feeder roots, proliferate near the soil surface where water and oxygen are more readily available. This is especially true in urban soils, which are typically shallow, compacted, infertile and droughty.

Water

Water transports substances throughout the tree and sustains its living cells. Water moves upward in a tree because the air is drier than the tree tissues. Only at 100 percent relative humidity does a tree stop losing water to the atmosphere. Like a sponge, air soaks up water vapor from the leaves and other non-woody plant parts in a process known as evapotranspiration. The water lost to the atmosphere is replaced by soil water, taken up by the fine root hairs just below the soil surface.

During the day, leaves give off water much faster than the roots can pull water from the soil. Since water molecules bond together very tightly, a continuous water column is pulled up the entire height of the tree. Evapotranspiration is most rapid when air temperature is high, the sun is bright, the wind is blowing, and relative humidity is low. The tension in the water column relaxes as the day wears on, temperatures fall, the sun sets, winds die and humidity increases. At night, roots continue to pull water into the tree, evapotranspiration slows down, and the tree is rehydrated by morning.

Nutrition

Trees are composed primarily of carbon, hydrogen and oxygen. Thirteen additional elements are required for healthy plant growth, but most are needed in minute amounts. Soils usually contain adequate levels of micronutrients. Major nutrients, particularly nitrogen, can be lacking in urban soils where topsoil has been removed, and leaves and twigs raked away. Fertilizer should be applied sparingly and only to correct a specific deficiency identified through lab analysis of soil and plant tissue. Excessive fertilization can damage tree roots and contaminate runoff.

Moving and storing food

Trees need adequate supplies of water, carbohydrates, minerals, and nitrogen to grow. Like blood, sap transports these vital substances to cells throughout the tree. Xylem sap transports mineral elements up through the tree. Phloem sap, which is bi-directional, carries most of the carbohydrates. Both xylem and phloem sap supply nitrogen.

In young trees, most of the carbohydrates produced in photosynthesis are sent to the roots before bud break. As buds open, the process is reversed, and carbohydrates are transported to the rapidly growing shoots. As shoots, flowers and leaves finish growing, food is directed to the cambium and roots for further growth. As trees grow larger, shoots growing near the crown, draw on food produced and stored nearer the treetop.

Unhealthy or damaged plants have few reserves and easily succumb to further damage. Important reserves are lost when roots are cut, crushed or suffocated. The tree responds with poor growth, premature leaf drop or by sacrificing specific limbs. Although symptoms may be delayed for several years, the damage is often fatal.

Repair

Trees cannot heal their wounds. They have no means of replacing damaged cells. Instead, trees produce chemical and physical barriers to seal off the wounded area. The tree forms a barrier over the damaged area with a new layer of wood. Together, these barriers form a compartment around the wound. This minimizes and blocks off the wound, reducing the area subject todecay. In general, the healthier the tree, the stronger the barriers, and the greater the resistance to decay.

Anchoring roots the right way

Pay attention to planting details today if you want a big tree tomorrow.

It doesn't take long to plant a tree. But the way you plant a tree today will make all the difference in its health, beauty and function over a lifetime – which could be a hundred years, or more. Plant a tree properly today and you'll be rewarded for decades to come.

Which tree to plant?

Plant the right tree in the right place! This guiding principle should govern your choice. Start by gathering information about the planting site. Your decision should be based on four basic factors:

Size: The tree must have enough space to expand to its mature sizevabove and below ground. Check the site for obstructions such asvoverhead utilities, buildings, or pavement, and be sure to call the statewide Diggers Hotline at 1-800-242-8511 to find out about underground lines. Do not expect that pruning will keep a tree within bounds. It won't!

Needs: Each tree species has specific requirements for soil type, pH, amount of moisture, exposure to wind, sun, and pollution. Review your site carefully and narrow the list of species to those that can prosper under the conditions of your site.

Diversity: So what if everyone on the block has birches in the back yard! Spend a little time identifying the trees in the immediate area, and select species for your property that will add diversity to the urban forest.

Landscape: You should certainly consider the role you want the tree to play in your overall landscape plan, but this shouldn't be your sole criterion for choosing a particular species. Thousands of trees die every year when design and aesthetics are placed ahead of biology.

Once you have decided which species to plant, take care to select a healthy, well-shaped specimen at the nursery. Poor form or other problems will be exaggerated as the tree grows larger, so take time and choose wisely now.

Preparing the site

For many years, we've been told to plant trees at the same depth as they were in the nursery. Nursery practices, often lead to 3-12" of excess soil heaped on top of the roots. Planting the tree at this same depth likely leads to problems later in the tree's life. These include trunk cracks and rot, crown die back and possibly girdling roots and premature death.

To determine the correct depth of the hole, measure the depth of the root system from the root collar to the bottom of the root ball. The root collar is the point where the roots end and the trunk begins. It is most easily recognized by a flaring at the base of the trunk. (Do not confuse the flared root collar with the bud graft, a swelling of the trunk where the bud of the cultivar was grafted onto the root stock. The bud graft is usually about six inches above the root flare.) When working with potted, containerized, or balled-and-burlapped plants, scrape the soil away until you reveal the root collar.

Dig the hole slightly shallower than the depth of the root system, and three times as wide. Leave an undisturbed pedestal of soil in the bottom for the tree to sit on. Taper the sides of the hole and use a shovel to rough up the exposed walls. Using a rototiller, shovel or spading fork, loosen the soil over an area outside the hole at least five times the diameter of the root system and eight inches deep. If the soil is compacted, loosen it up even deeper.

Planting the tree

At the nursery, tree stock come in three different types:

  • Bare root: Because the roots have no soil on them, they must be kept cool and moist at all times. Before planting, inspect the roots. Damaged or broken roots should be clipped using sharp hand pruners. Spread the roots out as you set the tree down on the pedestal. The root collar is plainly visible to judge proper depth. Bare root trees should be planted when dormant.
  • Potted or containerized: Cut and remove the container first, then carefully set the tree in the hole. Cut any large roots that encircle the outside of the root ball using sharp hand pruners. If the root collar is not visible, dig down until it is and remove excess soil from the top of the root ball.
  • Balled-and-burlapped: Remove the rope around the trunk, peel the top of the burlap back and check for the root collar. Carefully set the tree at the proper depth without disturbing the root ball, then remove excess soil from the top of the soil ball. Snip as much of the wire basket off as possible and peel the burlap down at least half way so the roots can expand into the native soil without restriction.

Whatever type of planting stock you're working with, make sure to place the root collar even with the soil surface, or one to two inches above grade. It's better to plant on the shallow side, as newly planted trees often settle a little. Plumb the tree and you're ready to begin backfilling.

Use the soil removed from the hole as fill. Don't use new soil, because it disrupts soil water movement. Break up large clumps of soil and discard large rocks and other debris. As you shovel soil over the tree roots, don't pack it down. Water and gravity will pack the soil naturally. Refill any air spaces that are caused by watering.

It's best not to fertilize at the time of planting. Wait at least one or two years, until the tree has recovered from the shock of transplanting.

Recreate nature's litter by applying a mulch of wood chips two to four inches thick over the entire area you rototilled or loosened with a shovel. Avoid placing wood chips directly in contact with the trunk. Mulch will keep the soil cool and moist, return important nutrients to the soil, encourage beneficial fungi and keep lawn mowers away from the tree.

Staking or guying new trees may be necessary if you're planting in a very windy spot or are planting bare-root stock, but it's best to avoid staking if possible. If you must stake, use wide bands of nylon strap or carpet to support the trunk and make sure the tree has room to move a little. Wire, even surrounded by a garden hose, causes serious damage to the trunk and should not be used. Don't pound the stakes through the planting ball, and remove all staking hardware within one year after planting. Studies have found that tree wrap does more harm than good, and should not be used.

A young tree needs all the energy it can get, so don't prune it. The leaves on the branches will help the tree produce the energy it needs to get established in its new location. Broken or dead branches and double leaders should be removed right away, however. Otherwise, it is best to wait two or three years for the first pruning.

Choosing an arborist

A tree professional, or arborist, can assist you with tree planting, pruning, fertilization, repair, disease and insect control, removal, and other services. Arborists understand the physiology of trees and base their recommendations and practices on that knowledge.

Here are a few things to look for when hiring an arborist:

Credentials:
A certified arborist has passed a rigorous exam and keeps up-to-date on the latest research and information through continuing education. Certification through the International Society of Arboriculture is one measure of knowledge. Membership in a professional organization such as the Wisconsin Arborist Association, the International Society of Arboriculture, the National Arborist Association, or the American Society of Consulting Arborists indicates an interest in professionalism.
Insurance:
Ask for certificates of insurance, including proof of liability for personal and property damage and workman's compensation. Then call the insurance company to make certain the policy is in force.
References:
If possible, look at jobs the arborist has done and talk with former clients.
Estimates:
Have more than one arborist look at your job and give estimates. Arborists are professionals, some charge for the first consultation, others don't: Ask!
Contracts:
Ask for a written contract which should include: exactly what work will be done, how it will be done and when; what cleanup work will be done; who gets any firewood; whether removal includes stump grinding, backfilling and seeding; the method of pricing the job and the total dollar amount you will be charged. Read it carefully and get your questions answered before you sign it.

Finally, keep these points in mind before you make any decisions:

  • Don't choose an arborist solely on price. Getting the job done properly and safely is more important than a low bid.
  • Beware of arborists who recommend topping a tree. Topping is appropriate only in extremely rare circumstances.
  • A conscientious arborist will never use climbing spikes unless a tree is to be removed.
  • Beware of door-to-door "arborists" offering a bargain, especially after storms.

A well-trimmed tree

Pruning improves a tree's structure and helps keep it healthy

A bit of judicious pruning benefits a tree at many stages of life. Properly pruned young trees will grow into handsome, structurally strong trees; they require little corrective pruning when older, and will pose less of a hazard from weak branches. Mature trees need periodic pruning to remove dead wood, crossed or rubbing branches, and to thin the crown to reduce the 'sail' effect.

Before you begin

Get out the whetstone! Pruning shears and saws should be sharp, for your own safety and to make clean cuts in bark and wood.

Pruning should always be done at branch junctions. Where two branches, or a branch and the trunk meet, there is an area called the branch collar. The ideal pruning cut leaves the branch collar intact while removing the rest of the branch. On larger branches, undercuts are necessary to prevent cracked branches or torn bark.

Pruning paint or wound dressing is unnecessary. Such sealers can actually hamper a tree's natural defense system, causing problems instead of preventing them.

Pruning a young tree

It's best to prune a young tree over a period of years. By pruning trees when young, the need for heavy pruning can be substantially reduced or avoided as the tree ages.

The first pruning on a young tree should take place about two to three years after planting. Pruning at this point will have the greatest impact on the future structure and form of the tree. Each cut has the potential to alter three growth, so remove no branch without a reason.

Stand back from the tree and look for branches that are broken, dead or diseased. Remove these problem branches first. If the tree has a double leader, one of them should be removed. Branches that are growing back into the center of the tree, and those that are rubbing against other branches also should be removed.

Take another look at the tree's overall form and structure before you prune any healthy branches. For most species, the main lateral or scaffold branches should ideally be spaced eight to 12 inches apart vertically and be evenly distributed around the trunk. The branches that are to remain should be no more that one-half the diameter of the trunk. Leave some branches lower down on the trunk – they'll help develop good trunk structure and may be removed during the second pruning. Never remove more than one-third of the total live crown at one time.

The second pruning takes place about five to seven years after planting. Again, remove defective branches first. Lift the crown and provide clearance for pedestrians, vehicles and structures by pruning the lower, temporary branches. Stand back and look at the form of the crown. Branches that extend outside the natural outline may be cut back to the branch collar.

Pruning the big trees

Mature trees need occasional pruning to remove dead or hazardous branches, to restore damaged crowns, and to keep roadways and sidewalks clear. Only experienced and knowledgeable arborists should prune mature trees. Arborists use a technique called "drop-crotching" to remove large branches and will never "top" a tree.

When to cut

The best time to prune is when the tree is dormant – after the leaves fall off in autumn, and before the buds begin to swell in the spring. The next best time is in the summer, after leaves are fully formed. Spring flowering trees are best pruned after the flowers have dropped. Try to avoid pruning any tree during leaf formation in the spring, or during leaf drop in the fall. Storm-damaged limbs, dead branches, or branches that may be hazards should be removed as soon as possible.

Ouch!

The common mistakes people make when tending their leafy charges.

Although we may not realize it, many of things we do in our yards harm trees, and it may be years or decades before the damage shows. Consider the following:

Wrong tree for the site: Often a tree is doomed before it is even planted. Because we like a certain species of tree, we plant it even though it cannot tolerate the site conditions. We plant tall trees under power lines or salt-intolerant trees next to roadways. Trees that need full sun are planted in shady areas. Short and wide trees are planted next to walkways. Poorly drained areas become home to trees that cannot tolerate wet roots. Trees are planted too close together or too near structures. Acid-loving plants are put in alkaline soils. Before choosing a tree, evaluate the site carefully and be sure the tree you choose is appropriate.

Planting too deep: Roots of a properly planted tree grow down and away from the trunk. If the tree is planted too deep – a common mistake – the roots will grow up toward the surface to get the oxygen they need to survive. As the trunk increases in size, it will someday come in contact with the roots growing laterally off the main roots. Soon the tree is girdled and killed by its own roots. This may not happen for 20 or 30 years, but that's the time the tree is at its highest value. Planting too deep can also cause root or trunk rot, internal cracking, and crown die back.

Topping: Topping trees is a crime against nature. Often done to reduce the height of a tree for safety, topping – incorrectly pruning branches so that stubs are left – accomplishes just the opposite. The stubs serve as entry points for disease and decay. Topping also causes a flush of fast growing but weak sprouts below the cut. The larger the sprouts get, the more hazardous they become.

Lawn mowers on the loose: Lawn mowers and weed whips kill more trees than nearly anything else. Be careful not to bang against trees with lawn mowers, or use trees as pivots to spin mowers around. A tree's nutrient and water transport system – its "veins and arteries" – are located just beneath the bark. Nicking or scraping through the bark will disrupt this system, weakening the tree and making it susceptible to decay. A large nick or scrape can kill the tree. A layer of mulch placed around trees helps control weeds, keeps the roots cool and moist, returns important minerals to the soil – and keeps lawn mowers at a safe distance away from the trunk.

Herbicide damage: Using broadleaf herbicides or "weed and feed" products can damage trees. A tree is a large broad-leafed plant. Products that kill your dandelions or lawn ivy will also kill your tree. Read product labels carefully and be extremely wary about using herbicides around trees.

Overfertilization: When a tree looks unhealthy, the initial response is to fertilize it. If a tree is under stress because it is fighting off injury, disease or insects, it must tap its energy reserves for defense and repair. Fertilizer, especially nitrogen, causes the tree to grow more leaves faster; the energy that should be used for defense and repair is redirected to growth. An overfertilized tree becomes more susceptible to disease and is in danger of using up all of its remaining energy reserves, leading to faster decline or death. While new leaves will return energy to the tree through increased photosynthesis, it may not be soon enough. Learn what is wrong with the tree first, then take appropriate action. Never fertilize before finding out what minerals are lacking in the soil and what effect the fertilizer will have on the tree.

Hot wires and high branches

Trees and utilities can co-exist – with careful planning and regular maintenance.

Midwestern landscapes are graced with lush green ribbons of trees that are essential to life. Across the land, the green ribbons are interwoven with silver strands – electric, telephone, cable television, water supply, wastewater and natural gas lines necessary for living in the modern world. We need both the green ribbons and the silver strands, yet they are often in conflict.

Jolted by volts

Trees and utilities frequently share a common corridor and compete for space. Conflicts between trees and most utilities are generally not serious, and can usually be dealt with by leaving a little distance between the two. Conflicts between trees and overhead electric lines, however, can have serious, widespread consequences.

Because trees contain so much moisture, they, like humans, are prime conductors for electricity. Overhead electric lines are not insulated. If you touch a tree limb in contact with a power line, you can be electrocuted. Trees must be kept clear of electric lines for that reason alone.

Conflicts between trees and overhead power lines can cause major disruptions in our high-tech, computer-driven, electricity-dependent society. Power outages and surges threaten life-saving medical devices in hospitals and interfere with public safety systems in police and fire departments, airports, schools, businesses and homes. Power outages caused by trees are costly to repair, resulting in higher electricity rates.

By law, utility companies must manage vegetation within and along power line rights-of-way to keep a "clear zone" around their facilities. These same state laws enable utility company employees and their contractors to enter all property to take care of any potential or real hazard at any time. Although utility companies make every effort to contact property owners well in advance of trimming work to discuss options, when emergencies arise, they can and will enter your property without prior notice.

For many years, utility crews and contractors topped trees, stubbing off limbs for clearance. Research has proven that topping causes serious long-term problems for the tree and increases maintenance time and costs. A more cost-effective approach, and one that is much better for tree health, makes use of directional pruning to train the tree to grow outside of the clear zone. This allows the tree to remain, coexisting with the power lines on that site.

Several Wisconsin communities have ordinances restricting planting beneath overhead power lines to low-growing species. Wisconsin's private, investor-owned electric companies all offer customers advice on selecting appropriate species for planting near lines. Wisconsin Public Service Corporation was one of the first utilities in the country to be named a "Tree Line USA" by the National Arbor Day Foundation for managing trees near overhead and underground utilities – proof that the green ribbons and silver strands can co-exist for the benefit of all.

Building for growth

Trees on construction sites need protection if they are to add value to the property in the years to come.

A four-year-old home sits neatly in the midst of 30 or so trees, the remains of a once-thriving maple forest now subdivided into half-acre lots. Although it's July, it looks like the last days of fall: What leaves are left have turned a dull, sickly yellow. The trees are dying, and the homeowner who shelled out $80,000 for a wooded lot wants to know why.

An arborist could spot the problem halfway down the block. The telltale signs of a grade change are evident: The trees look like telephone poles stuck into the meticulously leveled-and-groomed lawn. Few will survive, and the homeowners drawn to the lots precisely because of the trees will be disappointed for a long, long time.

The problems begin down below

Careless handling of building materials and equipment above ground can rip branches and tear tree bark. The real damage, however, occurs below ground. Soil compaction and altered grade within a tree's rooting area are the two primary causes for tree decline at construction sites.

Compaction is caused by heavy equipment – trucks, bulldozers, wheelbarrows, and stockpiles of wood, sheetrock, bricks and other building materials. The weight squeezes the air spaces from the soil, decreasing the oxygen tree roots need to live and grow. The hardened soil can no longer absorb water. Instead of soaking into the ground where roots can take it up, water runs off and trees become dehydrated.

Grade changes can also be fatal. Dropping the grade cuts into a tree's root system, most of which is within the top 12 inches of soil. Adding soil on top of tree roots has a compacting effect–as little as three inches of fill can literally smother roots. A tree trunk coming straight out of the ground, without the typical flare at the base as trunk changes over to roots, is a good indication that fill has been added and the grade changed.

Protecting your trees now for tomorrow

You can have a beautiful home and trees, but it requires planning and some work. The process begins before any earth is moved. Consider hiring a reputable arborist for assistance. Remember, the existing trees add a great deal of value to your property; it may take decades to replace them should they die. Keep the following points in mind to ensure the survival of your trees during and long after construction is finished:

  • Inventory all trees on the lot. Record the location, size and species. Include comments on each tree's overall form and health. Use this information to decide which trees should be saved and where the home will be situated.
  • Mark out the proposed location of the house on the site. Determine how much room is needed for machinery to maneuver during construction. Allow for a single entrance and exit corridor for all machinery, equipment and materials – preferably the location of the future driveway.
  • Select the trees to be saved and think carefully about future landscaping needs. Saving groups of trees is far more beneficial than saving single specimens.
  • Contact the utilities involved to see if a single corridor can be used for the electric, gas, phone, water and sewer service lines. By not crisscrossing the yard with all the different lines, you won't need to sever the root systems of many trees.
  • Meet with the builder and their subcontractors to outline 'tree protection' areas. Roots of trees can extend outward two to three times the height of the tree. Fence these areas off and do not allow equipment or materials within them.
  • Include a landscape protection clause in all contracts. Document the trees' condition prior to any site modifications with video or pictures.
  • Water the trees, if they need it, before, during and after construction.
  • Mulch under the dripline of the trees to be protected to minimize compaction, conserve moisture and add important nutrients back into the soil.
  • Prune any large dead limbs and live limbs which may be in conflict with machinery or the structure.
  • Monitor the construction process once it has begun. Visit the site regularly to inspect and take pictures or videotape. Your presence will alert workers of your concern. Should damage occur, notify the builder immediately, and take action to ensure continued health of the affected trees.

Growing together

There can be no urban forest without assistance from urban forest dwellers.

To survive, an urban tree needs routine care and maintenance; to thrive, it needs committed people. A community tree program guides the planting, management and care of trees in a town, village or city. Properly tended, trees become important community assets that appreciate in value with each passing year.

An effective tree program has four critical elements: Community support, adequate funding, ordinances, and a clear line of responsibility.

A board for trees

People readily recognize the trees in their backyard, but have a harder time envisioning the "forest" that encompasses all the trees within their village or city. A municipal tree board – generally a group of volunteers – can greatly contribute to the greening of a community by first increasing public awareness of the value of trees in town. In larger communities where responsibility for tree care may reside in a parks-and-recreation or public works department, a tree board can serve in an administrative, advisory or advocacy capacity. In smaller communities, a tree board take more of a hands-on approach, making routine decisions regarding trees, lining up volunteers and planting the local landscape. DNR's urban foresters can help communities develop urban forestry programs.

Some communities needs to back up their bark with bite. Community ordinances outline responsibilities for managing the urban forest, provide legal authority to conduct forestry activities, and define locally acceptable standards for management. Communities with a good set of tree ordinances in place will find it easier to carry out successful tree programs.

The city of Hartford in Washington County recently took legal steps to better protect its urban forest. "Our new tree ordinance, along with the tree inventory and plan, is something Hartford needed," said Brian Turk, Hartford city planner. "We have ignored our trees for a long time." Hartford's new ordinance makes the maintenance of street trees the responsibility of the public works department, a change recommended by the tree board. Previously, property owners were responsible for caring for street trees adjoining their land. The care was uneven, as residents weren't properly trained or regularly encouraged to maintain trees. The regular maintenance program provided for in the new ordinance was considered a small price to pay to protect the community's investment in a healthy stock of trees.

When you want to know and do more

If you have questions about your individual trees or home landscape, begin by contacting your community tree board or the staff at your local forestry or parks department for assistance.

Next, try your county's university extension office. Brown, Dane, Kenosha, Milwaukee, Racine and Waukesha counties have full-time horticulturalists; other coutnies have agriculture or natural resource agents that can point you in the right direction. Extension offices have bulletins and fact sheets on tree problems. UW-Extension has just begun a Tree Care Advisor (TCA) program to train citizens in basic tree care; check with your county to see if there are any TCAs available. If not, you could help start such a program.

A commercial arborist or tree service is your best bet if you need someone to visit your property to diagnose a tree program. See Choosing an Arborist for a few tips.

If you have a question about trees on public property or want to get invovled in an urban forestry prorgam, go to you local government first. All commuities will have someone in charge of trees. It may be the city forester or park director, or it may be the director of public works, the street superintendent, or a citizen tree board.

If your community doesn't have a program, DNR Urban Forestry Coordinators can help you start one. Coordinators provide information and can put you in touch with volunteer groups and consultants. Cost-share grants to fund urban forestry projects for communities are available. Urban Forestry Coordinators are located at DNR offices in Eau Claire, Green Bay, Madison, Milwaukee, Pike Lake State Park and Wausau.

If you'd like to do some research on your own, take a look at Urban Forestry by Robert W. Miller, the Journal of Arboriculture, and the Wisconsin Urban and Community Forests newsletter. Check your local library or World Wide Web search engine under arboriculture, forestry, horticulture, trees and urban forestry. Organizations, including American Forests, the International Society of Arboriculture, the National Arbor Day Foundation and the Wisconsin Arborist Association are good sources of information.

The DNR Urban Forestry program has a selected bibliography with a number of useful resources. Contact Richard Rideout or write DNR Urban Forestry Resource List, P.O. Box 7921, Madison, WI 53707 USA.

Contributing authors: Cindy Casey, Don Kissinger, Richard Rideout, Peter-Jon Rudquist, Kim Gorenc Sebastian, Dave Stephenson and John Van Ellis of the Wisconsin Department of Natural Resources Urban Forestry Program prepared the information for this article.

For a wealth of information on urban forestry (yes, even MORE than what you've just seen here), visit Urban and Community Forestry.

Tree trimmings – facts about trees
Bark can be very thin or very thick. The bark of a birch tree may be only a 1/4-inch thick, while the bark of a giant sequoia can be as much as two feet thick.

Ninety percent of a tree's roots are in the top 12 inches of the soil. Roots can extend up to three times the height of the tree. The notion that the roots of a tree mirror its crown is more artistic than accurate: The shape of a tree actually resembles a wine glass set on a plate. Root growth can occur any time the soil temperature is above 32 degrees F.

There are over 20,000 different kinds of trees in the world.

A large leafy tree may take up as much as a ton of water from the soil every day.

Trees make up an estimated 80 percent by weight of the 49 trillion tons of green plants on the planet.

It's not necessary to paint a tree wound after you remove a branch. In fact, research shows that painting wounds may actually do more harm than good. The only exception is if an oak tree is pruned or otherwise wounded between bud break and two or three weeks past full leaf development (generally April 15 to July 1). Oak trees are most vulnerable to oak wilt during this time.

A shade tree positioned on the west side of a home can keep it 20 percent cooler than a home without a tree. Trees are nature's air conditioners. The cooling effect of one tree is equal to that of five room air conditioners running 20 hours a day.

Trees: save energy by blocking winds and providing shade; intercept rainfall and reduce runoff; filter pollutants from the air; muffle traffic noise; reduce glare and reflection; define space; screen undesirable views; provide privacy; shelter wildlife; andadd color, texture and beauty to the urban environment.