Healthy Trees, Healthy Communities

This is the first guide to home tree care for Montgomery County, Maryland. It tells us why we want to take care of our trees and how. You can print directly from this format -- the entire document or a few pages. The website for the guide is under development and will be available at Please email us at with any questions or comments.



HEALTHY TREES, HEALTHY COMMUNITIES A Guide to Tree Care in Montgomery County, Maryland



“Arboriculture is not only the cultivation of trees. It is the cultivation of a community to which we belong.” - Alex Shigo, former USDA scientist and father of modern arboriculture



Acknowledgments Author: Caren Madsen, Conservation Montgomery Chair and Creator of Home Tree Care 101 Editor: Gary B. Ellis, Ph.D. Policy Editor : Amanda Farber, Conservation Montgomery Board of Directors Advocacy Committee The Montgomery County Government for supporting development of this guide though the Home Tree Care 101 Community Projects grant. Conservation Montgomery Board of Directors, for supporting development of this project. USDA Forest Service , for providing inspiration and information for the guide. Technical Reviewers Brett Linkletter, Montgomery County Department of Transportation

Christopher Myers, Montgomery County Department of Permitting Services Katherine Nelson, Maryland-National Capital Park and Planning Commission

Andres Ovalle, Consulting Arborist, Home Tree Care 101 Jack Pond, Consulting Arborist, Home Tree Care 101

Mia Rothberg, Maryland-National Capital Park and Planning Commission Kristin Taddei, Maryland-National Capital Park and Planning Commission Caroline Taylor, Montgomery Countryside Alliance Program Managers at the Montgomery County Department of Environmental Protection

Please send feedback or questions on the guide to Top cover image: Black Tupelo, adopted as the symbol of the official Montgomery County Tree

Note to Readers: Due to differing conditions of trees, tools and individual skills, Conservation Montgomery and the Montgomery County Government assumes no responsibility for any damages, injuries, or losses incurred because of using the information in this guide. The guide will be updated as new regulations and data are available. First edition: September 2023. Printed with 100% post-consumer recycled paper. Images and Graphics : Most images and graphics in the guide are the property of Conservation Montgomery, unless otherwise noted. Some images are courtesy of county, state, and federal agencies, such as the Montgomery County Department of Environmental Protection, Maryland- National Capital Park and Planning Commission, US Environmental Protection Agency, USDA Forest Service, and the US Geological Survey, and are in the public domain. Royalty free images were purchased from and are licensed to Conservation Montgomery. Before using any image or diagram from this publication, please contact Conservation Montgomery at






Part 1: How to Care for Your Trees

Chapter 1: Tree Anatomy

17 21

Chapter 2: Maintenance of Mature Trees

Tree Inspection

21 21 22 22 22 23 23 24 27 27 28 28 29 29 29 30 30 30 31 31

Watering Recommendations How to Use a Soaker Hose

How to Water Properly with a Garden hose Watering from Your Garden Hose Without the Nozzle

Making your Own Soaker Pruning Mature Trees

Where and How to Cut a Tree Branch

Soil Conditions


Fertilizing and Use of Herbicides and Pesticides How to Apply Fertilizer to Your Trees

When to Apply Fertilizer Where to Apply Fertilizer

Using Pesticides Safely in Montgomery County Care from the Bottom Up: Protecting Roots and the Trunk

Uninvited Guests: Invasive Vines

Using Trunk Guards and Care in Handling Bark Protecting trees during construction

Another Note about Bark

Chapter 3: Planting and Maintaining New Trees


Choosing the Right Tree Options in Montgomery County

33 33 35 36 37 38 38

DIY Tree Planting

How to Plant a Tree

Watering a Young Tree To Stake or Not to Stake? Pruning Young Trees

Chapter 4: Tree Concerns and Removal


Trouble-shooting Your Tree Condition

42 43


Chapter 5: How to Hire an Arborist or Tree Care Company




Part 2: Why we Take Care of Our Trees

Chapter 6: Why Trees Matter


Trees as Part of History

49 51 51 52 52 53

Benefits of Trees in Our Communities Stormwater Management Air Quality and Climate Change

Health, Social and Psychological Benefits of Trees

Economic Benefits of Trees

Chapter 7: State of Tree Canopy and Forest Cover in Montgomery County


Importance of Our Urban Forest and Tree-planting Programs

55 56 57 58

Forests in Montgomery County Planting Forests in Montgomery County

Street Trees – An Essential Part of Our Tree Canopy

Chapter 8: Looking Back


and Ahead at County Tree and Forest Policy

The Impact of Legislation


What You Can Do to Help Your Trees and Tree Canopy in Your Community Additional Resources




69 75 81






Trees provide us with so much more than beauty. Because of the immense environmental services they provide, we consider trees the workhorses of the environment. On our home lots, trees provide us with cooling canopy and increased property values. Many homeowners connect quality of life to the size and species of trees growing on their lots. Trees help mitigate the impacts of climate change. They sequester carbon, intercept stormwater, and reduce the urban heat island effect. They are a natural answer to a multitude of problems. Dr. Alex L. Shigo, considered the father of modern arboriculture, noted that, “Trees are patient.” Indeed, trees take decades to grow to maturity and can take decades to decline from old age, disease, storm damage or insect infestation. Caring for trees on residential or commercial property is essential for their longevity. This is the first guide specifically designed to help homeowners maintain their portion of our life-giving canopy in Montgomery County, Maryland. It is based largely on Conservation Montgomery’s experience with Home Tree Care 101 classes that have been held throughout the county since 2012. The guide covers information for all homeowners and renters, but also focuses on tree and forest programs in Montgomery County -- where the Black Tupelo was adopted as the symbol of the official County tree in 2022. The guide is divided into two parts – how to care for trees and why we care for trees. Chapter 1 gives an overview of tree anatomy so that you understand the important parts of a tree as you pursue tree care. Chapters 2 and 3 discuss care of mature and newly planted trees. If a tree struggles and fails, despite our best efforts, Chapters 4 and 5 will help you navigate signs of trouble within an individual tree. In Chapters 6 through 8 you will find information about why we want to care for trees. We cover the benefits of trees, the state of our tree canopy and forest cover, and what the future looks like for increasing our canopy. We also include how trees are literally part of our history. Please visit the online version of the guide at . Montgomery County residents are clearly interested in tree care and preservation of trees, so much so that residents were instrumental in including tree canopy and forest cover as elements of the Montgomery County Climate Action Plan . As a taxpayer in Montgomery County – and as a homeowner, renter, homeowners’ association member or apartment dweller -- we hope you will use this comprehensive guide to maintain trees in your community as a healthy and long-lasting part of the local tree canopy and forests. For our physical and mental health -- and the wellbeing of our county neighborhoods – a robust and healthy tree canopy matters now more than ever. Let’s work together to preserve these cherished titans of nature. - Caren Madsen, Conservation Montgomery



Part 1 How to Care for Your Trees



Chapter 1 Tree Anatomy

Trees are more than the sum of their parts. To fully appreciate proper care of a tree, it’s important to understand the basic structure and growth of a tree, not unlike how people in the healthcare professions must learn human anatomy and physiology before they can practice medicine. The eight basic parts of a tree are the leaves, branches, trunk, cambium, xylem, phloem, bark, and roots.

Parts of a Tree

The most aesthetically appealing part of a tree is the crown -- comprised of a tree’s branches and leaves. Besides its pleasing appearance, the crown is where food for the tree is formed via

photosynthesis. Photosynthesis is the process of using sunlight to turn carbon dioxide and water into sugar and oxygen. Without the process of photosynthesis, the earth’s atmosphere would be inhospitable to life as we know it. As we work our way down the tree, branches continuously merge at unions, eventually forming larger limbs. As limbs grow and converge, they gradually increase in diameter until they merge with the trunk. Professional arborists are trained to inspect these main unions where large limbs attach to the trunk, as this can be a common, and often preventable, point of failure in a mature tree. The trunk of the tree serves an obvious structural role, and its strength must be proportional to the size of a tree’s crown for a tree to withstand the forces of nature. It also functions as a highway for the transport of water, nutrients, sugars, and growth hormones.

The most visible parts of your trees will be some of the most important sections of the tree to protect.

Near ground level, a tree’s trunk transitions into the below-ground root system. This transition zone is referred to as a tree’s “root flare” or “root collar.” Force from a windstorm or other weather hazard is transferred through a tree and then distributed down to the root system through the root collar. This area can be a particularly vulnerable part of a tree since most wounds occur at ground level. Wounding or excessive moisture trapped against this part of a tree can invite decay pathogens to enter, which is why protective measures should always be taken during construction or re-grading (the addition or removal of soil) around a mature tree. Lastly, roots absorb and transport water, minerals, and stored energy in the form of starches. Roots also produce growth hormones that allow all parts of the tree to work in conjunction by sensing environmental risks such as drought and soil temperature. Roots anchor the tree and keep


it stable. Contrary to the commonly held misconception about trees having extremely deep root systems, 90% of a tree’s water and nutrient absorbing roots are found in the upper 18” of soil. Having a better understanding of where a tree’s roots are located, and how vulnerable they are, is critical information for any tree owner who may be remodeling and having construction activity on their property. Badly planned construction activity around a root system can eventually kill a tree.

Layers of a Tree

Starting from the outside of a trunk, the first (and usually only outwardly visible) layer of a tree is the bark. Think of bark as the outer skin of a tree. It is a protective covering and is composed of mostly dead cells. Bark keeps moisture and gases in the tree and helps a tree resist attacks by insects and disease. Exploring the center of the tree, the next three layers beneath the bark are phloem, cambium, and xylem. Cambium is a thin layer of cells that are critical to the growth of a tree. The cells of the cambium change to give outward rise to

phloem and inward to xylem. In general, the phloem transports sugars and growth-signaling hormones throughout the tree. Xylem transports water and nutrients from the roots up to the leaves. The active outer portion of xylem is also known as sapwood. The older, inactive parts near the center are heartwood. Heartwood is darker, stronger, and more resistant to decay.

Heartwood provides additional support for the tree. Trees are a wonderful marvel of self-sustainability. They absorb water, nutrients, carbon dioxide and sunlight to produce their own sugars via photosynthesis and can even store their sugars for later use in the form of starches -- all while reaching 100 plus feet into the air and remaining anchored during heavy winds.

The most visible parts of a tree are its first line of defense. Bark and tree roots are where trees often experience construction damage. High winds and other factors can shred and break even the largest limbs of a tree. As tough as trees are, preventing injury to their roots and bark is critical. Fortunately, most wounds to a tree do not lead to decay or hollows. Trees have an amazing ability to survive the most adverse conditions. Xylem is one of the tissues that transports water and nutrients through a tree. This shows where xylem is located in the trunk. Active xylem is sapwood, as shown in the tree trunk illustration.


Tree Defense Mechanisms

As living and complex biological structures, trees activate their own defense mechanisms when they sense a threat to survival. Trees grow and adapt in ways that allow them to compartmentalize and compensate for decay. Unlike animals, which can move to a safe place when threatened, trees are stationary and start a series of chemical processes to wall off or create a boundary around injury or infection. Trees have a remarkable ability to try and protect themselves. When the bark of a tree is damaged, the process of compartmentalization begins almost immediately. Boundaries, called reaction zones, will begin to form physical and chemical barriers around the site of the wound so the rest of the tree is able to resist infection. The seal eventually becomes a scar on the outer bark and may or may not disappear over time as the trunk continues to add annual layers of growth.

Human-induced tree damage. Even if you love someone, or love a tree, carving into the bark is not showing the tree love. In this example, the tree has compartmentalized and sealed over the wound created by carving.



Chapter 2 Maintenance of Mature Trees

Tree Inspection Awareness is key when caring for trees. And there’s no question that the lifespan of all trees can be extended with proper care. Get to know the trees on your property by observing them through each season. Learn what species they are and what characteristics are of that species. It will help you determine the proper care of each tree. Look at your trees from a distance and then close-up to check for signs of health and decline. Use the chart in Chapter 4 to assess whether pruning or a professional evaluation is needed. If a problem with a tree can be identified early enough, the tree might be saved and live for many more years. Diagnosis is typically best performed by a reputable Maryland Licensed Tree Expert (LTE) or a certified arborist.

Some of the most common symptoms of stress or disease within a tree can be easily spotted. For example, random shoots growing low around the main trunk of a tree indicate stress. This is called “adventitious growth” and warrants a closer look by a professional. Another sign of stress or decline is mushrooms growing at the base of a tree. You might look to see if sections of leaves are browning prematurely or if the leaves are smaller than other leaves on the tree. Before taking any drastic remedial measures, consult a Maryland LTE.

Mushrooms at a tree base can indicate stress for the tree.

Watering Recommendations One of the simplest but often overlooked ways to care for your trees is watering. The correct amount of water and the timing is critical from spring through early autumn and in dry winters. Mature trees may not need regular watering except during periods of extreme drought. Overwatering can harm a mature tree that has adapted to soil conditions. Water no more than one or two times a month to soak the top 18 inches of soil. You can use a screwdriver to dig down and check the top six inches of soil. If it’s wet, there may be no need to

Aim for the dripline of a mature tree when watering.


water. Avoid watering near the trunk and instead aim for the dripline of an established tree. The dripline is the area away from the tree trunk that creates a circle around the tree from the farthest extension of the crown to the ground. Water here deeply and thoroughly with a hose, or if the tree is within reach of a sprinkler, move the sprinkler around the outer dripline. When using a hose, place the nozzle around the dripline and away from the trunk. Tree Montgomery has excellent resources on their website for watering trees. How to Use a Soaker Hose “A soaker hose is designed to let water slowly seep out along the length of the hose. This saturates the soil around the tree by mimicking a gentle day-long rain. It’s convenient because you can leave a soaker hose in place during the summer. You can also cover the soaker hose with mulch to hide the hose and help disperse and conserve water.” i “If you are using a soaker hose, leave the water dripping for about one hour on one side, then switch the hose to the other side of the tree for another hour. You might want to use timers to automatically turn your outdoor faucet off. They are available online or at lawn and garden shops. Check the hose regularly to make sure the water drips out gradually along most of the length of the hose. Water should drip, rather than spray, from the hose; if it sprays, reduce the water pressure by turning back the faucet.” ii How to Water Properly with a Garden Hose “There are at least two ways to water using a garden hose. You can water with a slow drip from the hose. Turn on the water, then turn the pressure down (nearly off) so that the water slowly drips out – literally one drop at a time. This mimics a slow gentle rain. For recently planted trees, place the end of the hose in the mulch ring and leave the water dripping for about an hour. Watering from Your Garden Hose Without the Nozzle

This method mimics a summer rainstorm. Remove the nozzle from the end of your hose. Using a watch and a bucket, determine how long it takes to fill the bucket as many times as needed for 25 gallons. For example, if you have a 5-gallon bucket, how long does it take the garden hose to fill the bucket 5 times? Once you know how long it takes, then water each tree, within the ring of mulch for a new tree and within the dripline for a mature tree, for the time

needed for 25 gallons. This generally does not work on hillsides because the water runs down the hill too quickly. Do not water with a spray nozzle or sprinkler from your hose – this gets water to the surface but very little gets below the grass to the tree roots.” iii


Making Your Own Soaker “Gather clean, empty buckets or jugs. Pierce the bottom of each with five to 10 tiny holes to allow water to drip out gradually. For newly planted trees, place the full buckets in the mulch ring. For older trees, place the full buckets about four feet from the trunk. Check to make sure the bucket is empty in several hours. iv Remember to refill your containers as many times as necessary to give your young trees 25 gallons of water. We recommend placing rocks or bricks in the bottom of the buckets to keep them from blowing away or falling over. v ” Find more information about watering on the Tree Montgomery website. Reforest Montgomery also has a convenient sign-up option where you can get reminders about watering.

Pruning Mature Trees Along with watering, pruning is the most common tree maintenance procedure. Pruning has potential to change how a tree grows. It is a way of manipulating the architecture of the tree by removing parts selectively. (Find information about pruning newly planted trees in Chapter 3 of this guide.) The scaffold branches are a mature tree’s framework. A well-pruned young tree will develop a strong structure that will mean less pruning over the years. However, a young tree generally won’t need pruning for the first one or two years.

Proper pruning helps trees thrive. However, this homeowner may be pruning too close to the branch collar.

In a mature tree, sturdy scaffold branches will

provide a graceful and functional form for your tree. Poor structure is typically a tangle of overlapping branches that will rub against one another and result in a weaker tree. A tree’s secondary branches should be well-spaced and balanced in appearance. Watch for codominant branches in a young tree and remove branches that compete with a central leader. If a mature tree on your property has codominant branches, cabling the tree can prevent a large section of the tree breaking off in high wind. Cabling must be performed by an LTE and is not appropriate for every situation. This guide covers pruning that a homeowner can manage. Major pruning high within an established tree should be handled by a professional LTE. A trained professional can climb into a tree safely to prune, and cable the tree, if necessary. We’ll discuss how to find a tree professional in another chapter.

While a tree is young, secondary branches that compete with a central leader should be removed. When branches become codominant and result in multiple trunks in a mature tree, damage can occur easily in a storm or a large codominant branch may need to be removed later.


If, as a homeowner, you feel you need to get a ladder to climb and prune a tree, that is a signal that you should look for a professional to do the work. Your feet should always be on the ground when pruning your trees. Another red flag for your safety is using power equipment. Electricity flows through branches and chain saws can accidentally cut power lines and electrocute a property owner. It is illegal for anyone to prune or remove trees that are near or touching overhead electric lines unless they are a trained professional. Your safety should always be a priority when working with trees. There are different types of pruning – pruning for safety, to cut limbs that can fall and injure people or damage property and pruning for aesthetics and the health of a tree. There are times when pruning occurs naturally including in high winds. Removing dead and damaged limbs after a storm and making clean pruning cuts will help a tree thrive. Before pruning, stop and think about why you are pruning and how you intend to prune. Without clearly defined objectives, it’s easy to get carried away and over prune your young tree. Always prune with goals in mind. An image on the next page shows a few of the compelling reasons to prune your tree. Routine thinning to remove dead branches can improve form and reduce risks. Removing branches can also increase light and pruning lower branches can allow more overhead clearance under the tree. But routine pruning does not necessarily improve the health of the tree. Think carefully before you cut. Where and How to Cut a Tree Branch Good pruning respects a tree’s natural design characteristics. After establishing your goals for pruning, remember there are three recommended steps to a clean pruning cut. Here is the three-cut method:

1. To target your cut, find the branch collar. This is an area where a branch joins another branch or trunk that’s created by overlapping tissues from both the branch and the trunk. It’s typically an enlarged notch at the base of the tree branch. The branch collar should stay intact throughout pruning. Make a shallow notch below the branch collar and about two inches from the branch collar. This first cut prevents a falling branch from tearing the stem tissue as it pulls away from the tree. 2. A second cut should be made outside the first cut, all the way through the branch, leaving a clean cut. This cut will leave a short stub.

Image courtesy of Deep Green Permaculture

3. Cut the stub just outside the branch bark ridge or branch collar, completing the pruning cut. Leave a cut that faces slightly upward. It’s important for the third or final cut to be clean to reduce the chance that shredded or exposed tissue will attract insects or harmful bacteria.


You will need a good set of pruning shears and a small hand pruning saw. These usually have a curved blade and are easier to move around the interior of a tree than a larger saw. A lopper or pole pruner has a telescoping handle and will allow you to perform light pruning on upper branches. Wear work gloves and eye protection when working with your trees at home. You never know when a branch or part of it might flip toward your eyes. How often to prune and when will depend on the type and age of the tree. You will also want to prune and clean up a tree if there has been storm damage or if a limb has cracked and split off the tree. Again, keeping clean pruning cuts on a tree will reduce the tree’s exposure to insects and disease and enable the tree to eventually seal off the wound. How much to remove will depend on the size of the tree, the species, age and pruning goals. In general, no more than 25 percent of the tree’s live branches and crown should be removed at once. Cabling

Above: Reasons to Prune Trees. (Red branches are to be removed. Credit: Don Wittig, former Master Gardener, UMD Extension Service.

You may have a mature tree that has multiple large trunks. This may be the result of the tree not being pruned as a young tree to eliminate a competing dominant stem. Call a professional to explore cabling the upper sections of the tree. Cabling involves installation of steel or synthetic cable to provide extra support for large branch unions or multiple large trunks. Cabling can help stabilize upper sections of your tree during a strong windstorm. Cabling your tree will not have an impact on the visual appeal of the tree. Once in place, cables are hard to see when you look up into the crown of a tree. But bear in mind that cabling is not always the answer. Reduction pruning of a large limb can also improve a tree’s chances of long-term survival. . The following chart provides a general idea of when to prune your trees. Tree Type First 10 years 10+ Years after planting Fruit trees Once every 1-2 years Once every 1-3 years Broad-leaf trees Once every 1-2 years Once every 4-7 years Conifer trees As needed As needed

Protect your eyes when pruning.


Above all, never top a tree when pruning! Never allow a contractor to top one of your trees. It is mutilation that can slowly kill a disfigured tree. The Arbor Day Foundation vi provides eight good reasons not to top a tree. It’s worth noting that the Maryland Licensed Tree Expert Law prohibits those with licenses from performing this technique.

Why you should NEVER top your trees. Starvation: Topping removes so much of the tree’s leafy crown that it dangerously reduces the tree’s food-making ability. Shock: By removing the protective cover of the tree’s canopy, bark tissue is exposed to the direct rays of the sun. The resultant scalding can cause the tree’s death. Insects and Disease: The exposed ends of topped limbs are highly vulnerable to insect invasion or decay fungi spores. Weak Limbs: New branches that grow from a stubbed limb are weakly attached and more liable to break from snow or ice weight. Rapid New Growth: Instead of controlling the height and spread of the tree, topping has the opposite effect. New branches are more numerous and often grow higher than before. Tree Death: Some tree species can’t tolerate major branch loss and still survive. At best, they remain weak and disease prone. Ugliness: A topped tree is a disfigured tree. Even with new growth it never regains the grace and character of its species. Cost: The true cost of topping is often hidden – lower property values, expense of removal and replacement if the tree dies. From the Arbor Day Foundation


Soil Conditions If you are caring for an established tree, soil conditions are probably something you have little control over. But check the soil around the tree periodically. Is it compacted? If so, a tree care expert can advise and perhaps work with compacted soil to aerate it. Tree roots have a better chance to spread more and stay healthy in aerated soil. But the less disturbance at base of a tree, the better. If you are considering using fertilizer, conduct a soil test first to see what nutrients the tree might need. Again, this would be a time to consult a Maryland LTE who can test the soil and advise on whether to fertilize and how. Soil is active and alive, filled with millions of microbes that provide important nutrients to a tree. Soil

also provides pathways for mycorrhizae. Mycorrhizae are healthy fungi that enhance uptake of water and nutrients for a tree. Mycorrhizae usually appear in soil as a fine, white substance in healthy soil. In Peter Wohlleben’s The Hidden Life of Trees: What They Feel, How They Communicate, Discoveries from a Secret World , the author discusses how microscopic organisms in mycorrhizae can travel great distances in soil. Soil is host to a hidden world beneath the ground that can nurture tree roots. Mycorrhizae form a symbiotic relationship with soil and the roots of a tree. Mulching

Rich, healthy soil is full of microorganisms.

Mulching your trees provides the roots with protection and helps the tree survive temperature extremes. It reduces competition from weeds and grass. Mulch also improves soil structure and releases nutrients as they break down over time. A ring of mulch can create a safe space where lawn mowers and weed whackers will not be used directly at the trunk. Over-mulching a tree is where our best intentions can go wrong. We’ve all seen the classic “mulch volcano” around the base of a tree. Even the best landscaping companies can sometimes make this mistake. Most “mulch volcanos” are a mound of mulch mixed with soil and clumps of grass piled around tree trunks. Or a mulch volcano can result from piling commercially sold mulch too high.

Spreading mulch so that the material is directly up against the base of the tree trunk is another common mistake. It can lead to moisture being trapped close to the trunk. This can form a damaging fungus that can create root rot and eventually kill a tree. Apply mulch between two and four inches deep and near – but not touching – the tree trunk. Mulch should typically extend to the dripline of a newly planted tree. For a mature tree, mulch as far a distance from the trunk as you can without losing the character of your landscaping. Use mulch made from organic material like wood chips and leaves. Check your mulch each year to see if more is needed.

Keep mulch away from the immediate base of a tree trunk. Pull it back about three inches away from the trunk. And avoid a mulch volcano.


Fertilizing and Use of Herbicides and Pesticides We recommend caution when you consider fertilizing trees or using chemical herbicides or pesticides around the base of a tree. The more we alter conditions by using chemicals, the more vulnerable a tree is to damage from overuse or misuse of chemical compounds. When injury results in a tree due to fertilizer burn, it is usually difficult to correct. If an established tree is in the right native soil, most likely it already has access to the nutrients it needs to flourish. Mulching is the safest and most economical way to fertilize a tree. Nitrogen fertilizer should be applied only if an arborist or soil test indicates that it’s needed. Fertilizer not absorbed into soil can pollute the environment; overdosing can harm or kill your tree. Using fertilizer during hot weather can also severely damage your tree.

Occasionally, if you have hired an arborist or a Maryland LTE to evaluate a tree, they might recommend fertilizing an older tree that is showing signs of distress. Our bottom line: Use a soil test kit and test before fertilizing or consult an expert before applying fertilizer to tree roots. Trees growing in the right soil typically will not need to be fertilized. If an expert recommends fertilizing one of your trees, or if you have used a soil test kit to find the correct mix for fertilizing a specific tree and want to do the project yourself, we offer the following guidance.

Always test soil before applying fertilizer. Otherwise, you can create an imbalance in soil composition that can upset the health of a tree.

Based on the results of the soil test, head to your local home improvement store to buy the fertilizer. Tree fertilizer is not the same as fertilizer for grass. Look for “Deciduous Tree” or “Evergreen” and water insoluble nitrogen (WIN) on the label. You should use a slow-release fertilizer to protect the quality of water in our watersheds. Always follow the directions on the label of the fertilizer. vii How to Apply Fertilizer to Your Trees viii ● Before fertilizing, use the information from soil testing to determine what nutrients are needed, how much to apply and when. ● Choose one of the following three methods of application: o Fertilizer stakes: Push fertilizer stakes into the ground below the roots of the grass. You will need gloves and a mallet to hammer the stakes about 10 inches into the ground. o Granular fertilizer: Dig or drill 10-inch-deep holes into the soil. Anything that can be used to plant flower bulbs will work well to dig the holes. Some home and garden stores rent or sell small augers. Place the granular fertilizer into the holes. o Liquid fertilizer: Inject liquid fertilizer 8-10 inches below the surface into the soil with a probe. This is the preferred method of the pros, but unrealistic for most homeowners without the special tools.


When to Apply Fertilizer ● Follow the directions from the results of your soil test. ● Time it right:

o In October or November to encourage root development; or o In March or April to encourage tip and leaf growth. o Do not fertilize in the hottest months of the year. Dehydration and excess fertilizer salts in soil can spell disaster for a tree. ● Never fertilize a newly planted tree – mulch is best for the first 3-4 years after planting. Where to Apply Fertilizer ● Put fertilizer stakes or dig the holes for granular fertilizer under the branches of the tree in a grid formation, about every two ft. ● Start at the outside, or to the soil starting at the tree’s dripline, and go in towards the stem of the tree. ● For all trees, stay at least four feet away from the trunk of the tree and work out to the tips of the branches. Using Pesticides Safely in Montgomery County In 2015, the Healthy Lawns Act (Bill 52-14) was passed to restrict the use of lawn care pesticides on both public and private property. Montgomery County was the first county in the nation to enact such a law. More than 50 organizations, including Conservation Montgomery, partnered with the nonprofit Safe Grow Montgomery to advocate for the Healthy Lawns Act. You must comply with county law when using pesticides or chemical herbicides that are suspected or have proven to be carcinogenic for humans. Montgomery County’s pesticide law restricts the use of certain pesticides on private lawns, playgrounds, mulched recreation areas, and childcare facilities. Most synthetic pesticides are not allowed to treat pests in lawns. Weeds and pests can be prevented by practicing organic lawn care, which should not require the use of

any chemicals. Safe Grow Montgomery’s extensive webpages, along with County websites, highlight the tips and tools for successful organic lawn care. Only organic or minimum-risk pesticides are allowed for use on lawns, playgrounds, mulched recreation areas, and childcare facilities. Some exemptions apply. Montgomery County law allows the use of EPA- registered pesticides which have active ingredients approved by the National Organics Standards Board; and pesticides which have ingredients that don't require EPA registration.

Approved signage for Montgomery County.


Care From the Bottom up: Protecting Roots and the Trunk.

Roots are an essential part of a tree. It is primarily through the root system that a tree survives the elements over decades. According to author Peter Wohlleben, the delicate root system of a tree might be considered its “brain.” The roots take up water and are where a tree stores all chemical activity and most of the nutrients within the tree. When a root grows outward, it responds to stimuli. As discussed earlier, a tree will react and try to anchor itself from the

roots up when wind moves the branches of the tree. One of the most common problems that property owners may notice is girdling roots. Roots that girdle and encircle the trunk of a tree will cause the tree to have health issues. Girdling roots grow across one another and wrap around the stem or trunk of the tree. They can cut off the transport of water, nutrients, and food and constrict the growth of a tree. The best way to deal with girdling roots is prevention. If you plant a tree, make sure the root collar is at ground level and circling roots have been straightened out. If your tree is older and already has girdling roots, consult an arborist or LTE about possible remedies. Don’t try to cut into the root system and prune roots yourself. You may cause irreversible damage. Uninvited Guests: Invasive Vines In Montgomery County, invasive vine removal is always recommended when caring for a tree. Left to grow on a tree, vines can eventually kill the host tree. English ivy is an invasive commonly found on county trees, along with bittersweet, wisteria, honeysuckle, porcelain berry, grape, and kudzu. To remove an invasive vine without damaging the bark of the tree, clip the vine all around the tree trunk at about four feet above the ground and at the base of the tree. Leave the vine on the tree and the invasive vine will die. Pulling at it can injure the bark. If you can clip or pull away where the vine is Crossing and girdling roots can inhibit tree growth. Image courtesy of University of Maryland Extension Service.

growing at the base of the trunk, remove it gently. Invasive vines need to be monitored throughout the growing season to make sure they don’t reappear on the trunk. If you are dealing with poison ivy, make sure you wear gloves and handle the vine away from your body. Dispose of it without composting it. Using Trunk Guards and Care in Handling Bark Deer, string landscape trimmers, lawn mowers bumping into a tree, and car doors hitting a tree can wreak havoc on thin bark that can be easily damaged. Deer and rodents like to chew on bark. And deer rub their antlers on trees to remove velvet and leave their scent. Trunk guards, or arbor guards, are essential to protect the lower trunk of a tree. Visit the Tree Montgomery or Reforest Montgomery websites for more tips on protecting young trees from damage. You can make your own trunk guard by installing

Deer guard to protect a young tree.


chicken wire, plastic tubing, or stiff wiring around the base of a tree. The guard should be at least four feet in height. One to four inches of space should be between the tree trunk and the guard. As the tree grows, the trunk guard will need to be replaced or removed.

Protecting Trees During Construction

If you are planning to build or remodel your home, part of pre- construction planning should be a discussion of tree protection. Trees located too close to construction are at risk. Heavy equipment or loaded pickup trucks parked at the base of a tree will destroy its root system and compact its soil. Cement mixers, paint cans or tools near a tree can also be damaging. Talk with your contractors and get a tree expert involved early in a consultation on tree protection measures. To minimize damage, you or your contractor should install a barrier of orange fencing and an “off limits” sign around the perimeter of your treasured trees. Tell contractors where they can park vehicles and walk on and off the property as well.

Montgomery County street trees are protected during construction.

Another unintentional way to kill a tree during construction is changing the grade of the soil surrounding a tree. Adding or removing as little as two inches of soil can have an adverse impact on roots and soil quality. And remember to keep your trees watered and mulched during construction. Your trees should be monitored and protected throughout the construction phase to make sure incremental and minor damage doesn’t become a larger problem for a tree, post-construction. After your building or remodeling project is finished, hire an arborist to advise on rejuvenating your trees by aerating root zones as needed, repairing bark and trunk wounds, treating crown injuries, and/or fertilizing if it is needed. Remember that you may not notice minor and incremental damage that is obvious to a trained arborist or tree care expert. Once in decline, it takes a tree a long time to die, and removal can be emotionally taxing and expensive. Another Note about Bark

Loose bark from the edges of a tree wound should be trimmed back to bark firmly attached to the sapwood (the layer of wood under the bark). Carefully remove all shredded sapwood, too, and leave a smooth surface. Leave old bark wounds undisturbed, especially when callus or tissue has developed along the outside edge of the wound. Trees protect themselves from decay organisms through compartmentalization, and callus tissue is part of that defense mechanism. Review Chapter 1 for more on tree defense processes.



Chapter 3 Planting and Maintaining New Trees

Choosing the Right Tree When you want to plant a new tree on your property, making the right choice is important for several reasons. First, consider a native tree species. A broad definition of “native” when referring to vegetation is “any plant that historically grew in North America.” ix Trees that grow well in Montgomery County could be species that have adapted to conditions throughout the Mid-Atlantic, Piedmont or Southeastern regions of North America. Natives generally will grow better than a nonnative tree that is incompatible with local topography, water, terrain, and climate. Over time, various tree species might also adjust or evolve to deal with climate change. Therefore, the authoritative lists x of native species may change over time. xi There are over 60 species of native trees in Maryland. A list of native trees is available on the Maryland Natural Resources website and in the online resources that accompany this guide. Many local nurseries also sell only native trees. Think about where you want to plant a tree and what you want in terms of aesthetics or purpose of planting in that spot. Are you looking for shade? Do you want to provide a complement to your landscaping design? Do you want a good habitat for birds and wildlife? Are you looking for a tree that will grow fast or be low in maintenance? The Maryland native tree list and some of the resources in this guide will answer a lot of these questions. For another reference, the local Reforest Montgomery program has a list of native trees on its website. Options in Montgomery County government and nonprofit organizations with experts who can help you choose the right tree. Whether you have a young tree or mature trees on your property, you can request a Home Tree Care 101 class for your community and learn how to maintain your trees. Tree Montgomery is a program set up to plant free shade trees across Montgomery County, Maryland. The program’s goal is to plant shade trees and increase tree canopy in our communities. Tree Montgomery staff will work closely with you to choose locations and species to plant on your property. Then they will plant shade trees for you and help with initial care of your new trees, all for free. Tree Montgomery accepts applications year-round, works with residents for up to a year and prioritizes areas based on equity, stream quality, development activity and lack of existing canopy. Reforest Montgomery’s free tree program aims to increase tree canopy in urban areas of Montgomery County. Properties in Montgomery County’s priority funding areas are eligible to apply for free trees from Reforest Montgomery, and applications from the county’s Equity Focus Areas identified by the In Montgomery County, we’re fortunate to have programs to assist residents in getting trees planted on their property at no or little cost. Programs like Tree Montgomery, the MCDOT Street Tree program, and Reforest Montgomery are managed by county government, state


county government are given priority. Priority funding areas are home to 98% of the county’s residents, but just 36% of the county’s tree canopy. xii Applications for fall plantings are

accepted starting February 1 of each year, while applications for spring plantings are accepted beginning October 1 of each year. Property owners and representatives can apply for up to six trees per season and can request trees from a list of 20 native species. Reforest Montgomery’s native tree coupon can be used at participating nurseries and garden centers in the county to receive a $50 off on any qualifying native tree with a retail value of at least $75. This $50 coupon can be combined with the State of Maryland’s $25 Marylanders Plant Trees coupon for $75 off the price of a tree that qualifies for both programs. There are several resources available on the Reforest Montgomery website for property owners looking to plant trees themselves using the discount, including a guide for planting, and caring for new trees, and a species list with information about the unique needs and characteristics of qualifying native species.

If you own property in Montgomery County’s Agricultural Reserve, you might be interested in reforesting a portion of your property for free through Re-Leaf the Reserve, a program of Reforest Montgomery and a partnership between the Montgomery Planning Department and the nonprofit Montgomery Countryside Alliance (MCA). Re-Leaf the Reserve is specifically for reforesting the county’s valuable 93,000- acre Agricultural Reserve and is MCA’s practical response to the growing climate change crisis. Two hundred trees per acre makes a forest. A forest can absorb 68 tons of carbon - or the equivalent of taking 17 cars off the road for a year. xiii As of this writing, Re-Leaf the

Reserve had reforested 15 acres of property. Property owners with an established forest conservation easement and at least 0.25 acre of unforested area, and property owners with 1 acre or more open space adjacent to a stream or existing forest, who are willing to establish a new Category I conservation easement, are eligible to apply for free reforestation through the program. Applications and planting opportunities in four priority watersheds and special protection areas are given precedence, though property owners outside of these areas are also encouraged to apply. (You can locate the watershed in which your home or business is located by visiting the Planning Department atlas of watershed and related information at or visit the county Department of Environmental Protection website.) The program aims to expand forests by planting forest edges, replacing forest lost due to invasive pressure, pests, storms, or heat stress, reforesting stream buffers, and reducing mowed areas. Both Tree Montgomery and Reforest Montgomery require applications to be submitted (except for the Reforest Montgomery native tree discount program). If your application to the Reforest Montgomery free tree program is not accepted by that program, Tree Montgomery may be able to provide you with free trees. Not all programs are available to all county residents. For example, the Cities of Rockville and Gaithersburg are ineligible because those areas do not participate in the county Tree Canopy or Forest Conservation Laws which both fund replanting.


Whether your trees are established or newly planted, Home Tree Care 101 (HTC 101) classes can help you care for your tree (s). Classes are available through a partnership between Conservation Montgomery and the County Department of Environmental Protection. If you organize a neighborhood class, a certified arborist will visit your community to walk around and evaluate trees on home lots. The arborists also offer hands-on demonstrations of pruning, mulching and tree care that you can manage at home. The classes are available in the Spanish language as well as in English.

If you are yearning to have a new street tree planted near your property, yet another option is available. The County Department of Transportation (MCDOT) manages the street tree maintenance program and planting of trees in the Right of Way. You can call 311 or go to the County Government website to request that a street tree be planted. MCDOT determines the location and species of trees that may be planted in the ROW and plants large shade species wherever possible to maximize canopy cover in the county. (See Chapter 7 for more on the county street tree program.) DIY Tree Planting If your heart is set on choosing and planting a tree, do a little homework before you head to a local nursery. The Montgomery Parks Department periodically offers horticulture classes, either online or at Brookside Gardens. Look at the Parks Department website to see if there is a topic that would be helpful. Locating a site for your tree is crucial to the success of the project. First, look at the site you have in mind and decide what size and species will be best suited to that location. For example, planting a fast- growing shade tree too close to your house might not work out well. The tree may grow to be too large for its location and may eventually give you more shade than you want in that location. An understory tree such as an Eastern redbud or a flowering dogwood might be a better choice. If you have ample overhead clearance and the right light and soil conditions, a shade tree will give you years of environmental benefits and an aesthetic focal point for your landscaping. You will want to avoid planting what will grow to become a tall shade tree under utility wires. You certainly want to avoid cutting into a gas line that can result in an explosion. In 2021, Maryland passed a “Miss Utility Dig Law” to prevent accidents involving underground utility lines. Call 811 to get a site checked and marked for utility lines before you dig. When you plant a new tree, you have the advantage of putting the tree in a place where soil conditions are optimal for that species. Before purchasing a tree or putting a shovel in the ground, look at the soil and put your hands in it. Some of the characteristics of sustainable soil xiv include: ● Drains well and is not compacted. ● Does not crust. ● Soaks up heavy rains. ● Stores moisture in droughts. ● Resists erosion and nutrient loss. ● Supports high populations of organisms like fungi, worms, nematodes, algae and insects.


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