Blog on Arbor Day Foundation website – written by James R. Fazio – February 15, 2018
Trees in a forest are usually thought of as fierce competitors, each struggling for control of available light and soil moisture, usually at the expense of neighboring trees. But Canadian researcher Suzanne W. Simard and her colleagues found that Paper Birch trees can actually aid their neighboring Douglasfirs.
*shared from Tree Services Magazine article by Sharon Lilly from 1/1/13
There may be a battle brewing on your property between your trees grass. Trees and turf tend to be mutually exclusive in nature; you don’t see many trees growing in the prairies or grasslands as you may have noticed that grass is not common on the forest floor.
Our urban landscapes represent an unnatural ecosystem in which we force two somewhat incompatible plant types together and expect optimum performance from each. Trees and turf compete for sunlight, water, mineral nutrients and growing space below ground. Turf roots typically outcompete tree roots and win the belowground battle. However, the dense shade of a tree’s crown can be too much competition for turf, and trees win the aerial war.
Shade leads to reduced grass density, increased root competition and increased weed invasion. There are some varieties of turf that are somewhat shade tolerant, but this may be a partial solution, because shade-tolerant grasses tend to be less tolerant of wear.
Pruning for light penetration
Pruning to increase light penetration should be considered, keeping in mind that it is not a permanent solution. An important axiom to remember is that trees will grow into the voids created by pruning. Keep in mind the old rule of thumb not to remove more than one-fourth of the tree’s foliage-bearing crown in a single pruning. If a tree is topped or thinned too much, it will be stressed and will probably produce many water sprouts (suckers) along its branches to compensate for lost foliage. This defeats the purpose of pruning to allow more light penetration.
It may help to “raise” a tree’s crown to improve light penetration. Crown raising involves the removal of lower branches, and most tree species are tolerant of this pruning practice. Crown raising, however, does not significantly increase sunlight to the turf in most cases.
Some trees have a tendency to form surface roots, which can be a major problem in lawns. Besides ruining the appearance of the turf, they can interfere with mowing equipment, and can even become a safety hazard. Homeowners always want to know to what extent they can prune or remove tree roots without bringing about the demise of a tree. Since cut roots tend to develop more roots, root pruning is usually not a good solution.
The most simple maintenance recommendation is perhaps also the most important: mulch. Mulching the root areas of trees is probably the least expensive but most beneficial thing you can do to enhance tree health and minimize competition with turf. Mulch helps retain soil moisture, moderates soil temperature, and reduces competition from weeds. Organic mulch can help condition the soil and improve microbial activity.
Apply mulch about 3 to 4 inches deep, but do not pile it against the trunk of the tree. As far as the trees are concerned, the bigger the mulched area the better. Group trees together in mulch beds and extend the mulched areas as far out as practical.
There is a long-standing, but inaccurate, belief that trees must be “deep-root” fertilized. This belief is associated with the myth that a tree’s root system is an underground mirror of the crown. Because most of the absorbing roots are actually in the upper few inches of soil, it makes little sense to place the fertilizer deeper.
If the lawn is being fertilized and trees are occupying the same area, the trees might not require supplemental fertilization. The key to any fertilization program is to base the application on the plant’s needs. Soil and foliar analyses can provide the information required to make an educated decision about nutrient needs.
Mowing equipment and string trimmers can damage trees. Most people don’t realize the degree of damage that can be caused by the bumping of a mower or the whipping action of the nylon string in a trimmer. A tree’s bark can provide only so much protection against these devices. Young, thin-barked trees can be damaged almost immediately. In the worst-case scenario, the trees are eventually girdled and die. Those that are not killed will be stressed. The wounds may serve as entry points for diseases, borers or other insects. Many canker rot and root decay fungi have entered trees from wounds created by lawn and landscape maintenance workers.
Herbicides, especially broadleaf weed killers, are often used on lawns. Since most trees are broadleaved plants they can be injured or killed if high enough doses reach them. Homeowners must keep in mind that “weed and feed” fertilizers contain herbicides that can damage trees.
Achieving a balance
Trees and turf can peacefully coexist and even thrive together in a landscape. Armed with an understanding of how each affects the other, you can modify your landscapes and adjust your maintenance procedures to optimize the growing conditions for both.
In November we’re starting to think of oyster dressing, pumpkin pie and turkey dinners, despite the fairly mild temperatures and presence of still-green leaves on many Maryland trees. While the leaves are past peak and have even started to drop in western Maryland, the brilliant orange, scarlet and yellow foliage is coming on strong in central Maryland and the mid-Eastern Shore.
In the central region, reports from Patapsco Valley State Park indicate a colorful scene. For fabulous views of fall foliage, stop by the Valley Overlook in the Hollofield Area near Ellicott City in Howard County. It’s also a perfect time to take in the two-mile scenic drive along Orange Grove Road in the Avalon Area, near Elkridge. With the weather expected to be cool and clear over the next few days, why not enjoy a hike in the park’s McKeldin Area in Marriottsville.
Equestrians can enjoy riding at Morgan Run Natural Environment Area, which reports fantastic conditions right now. Located in Carroll County, this relatively undisturbed area has 7 miles of trails running through old farm fields and forests.
Baltimore, Carroll and Harford counties are nearing peak, with most understory trees (dogwood, spicebush and sumac) as well as black gum, cherry, hickory, red maple, sassafras, sweet gum and yellow-polar near peak. Sugar maples changed a little and then lost their leaves, which is becoming typical for this season.
Although the recent storm accelerated leaf dropping, the Route 1 corridor from Forest Hill to Fallston can compete with anything New England has to offer. The burning bush is flaming and the maples are quite brilliant. Grass is still green making for a colorful contrast.
At the top of the Chesapeake Bay, Elk Neck State Park in Cecil County is reporting some beautiful conditions right now, with foliage about 50 percent peak. The park’s sandy beaches, marshlands and heavily-wooded bluffs comprise the peninsula formed by the North East and Elk rivers and the Chesapeake Bay, and several trails meander through the diversified topography, revealing a great variety of plant and animal life. An easy walking trail to the Turkey Point Lighthouse provides a fantastic view.
On the upper shore in Kent and Queen Anne’s counties, red maples are still turning orange/red in most areas. Willow oaks are still green as are most of the oaks although some have turned brown. Dogwoods are deep burgundy and starting to lose leaves. Woodland areas are showing some signs of yellow.
Maryland’s mid-shore is about mid-peak, with oaks just beginning to turn. Colors are lovely, in a water-color sort of way, as seen in the photo of Wye Mills Lake.
The leaves are just beginning to turn in Wicomico and Worcester counties; however, rain and high wind brought down some of the early color.
Montgomery County reports a lot of color change during the past week. Oaks and maples are quite colorful in Prince George’s County as well.
Tulip poplars and gums have completely turned color. In Southern Maryland leaves are now starting to turn in Calvert and Charles counties, while St. Mary’s is mostly yellow with some red appearing on the maples.
Even after a tree is selected and installed based on the site conditions of sun, shade, soil drainage, proximity to other trees and shrubs, nutrient availability, desired size, slope, surroundings, adjacent activity and more, it can fail to thrive.
Sometimes that’s because the tree wasn’t chosen well and sometimes it’s because it wasn’t planted well. But even more critical to the tree’s success is where it was planted. A tree’s proper location usually will determine whether it becomes an asset or detriment to the landscape.
Tried and true: RPRP
The gold standard of “Right Plant, Right Place” still reigns supreme.
Most arborists would say failure to mind this guiding principle begins with a lack of consideration for the tree’s size. Many reasons exist for this, including lack of foresight and denial that a certain species will actually get that big or wide. Many property owners are too lazy or self-centered to consider the future of their land and the potential ramifications associated with it.
The next consideration is the square footage of available rooting space required for adequate growth, nutrient absorption and structural and support. Although it’s a gross generalization, the average shade tree requires about 1,000 square feet of unimpeded surface – either covered by turf, mulch or groundcovers – in which to grow. In many locations, this much space isn’t provided.
The desired shape of tree – vase, cylindrical, rounded – also can play a role in RPRP. Some sites allow these forms to grow and develop well, and others don’t. The ones that require the largest available space are often limited on site.
The availability of sunlight is a key consideration when choosing tree species, as many require full sun exposure, while others are tolerant of, or actually prefer, shade. Species such as serviceberry, pagoda dogwood and redbud are often poorly sited as a result of this factor.
Tough sites and why
Unfortunately, many sites are compromised in one way or another. These are the most common tough sites.
Slopes: Gentle slopes are desirable; a 2 to 3 percent drop-off facilitates water movement away from buildings, yet generally allows for water movement downward through the water profile. When the degree of slope is 5 to 10 percent or greater, problems commonly arise in tree performance and landscape maintenance. At least four undesirable outcomes are associated with a severe slope:
- Decreased infiltration rate: On slopes, natural rainfall and irrigation water isn’t absorbed as quickly as at the top or bottom. Trees growing on the face of the slope often suffer from inadequate moisture in the root zone.
- Difficulty in mowing: When turf grass is grown on the slope, an increased chance exists for the mower to slip and slide, potentially striking the tree trunk or lower branches, causing damage.
- Difficulty in application of fertilizers and pesticides: After landscape maintenance products are applied on slopes, there’s a tendency for them to move downward, especially when granular products are used and/or moderate to severe rainfall occurs after application.
- Difficulty in mulch retention: Over time, mulch pieces tend to drift downward or sideways on slopes, moving away from installed landscape plants.
Hell strips: The thin, narrow and sometimes oddly shaped portions of the landscape often provide an inhospitable location for trees to grow well. The lack of available rooting and absorptive space is the main limiting influence. In northern climes, hell strips (also called tree lawns or devil strips, depending on your region) are often the space between the sidewalk and a street; in these situations, applied salt and sand for winter traction control causes damage and adds to the lack of rooting. In general, the siting of woody plants in these locations should be carefully considered.
Parking lots: Parking lots offer many of the same negative influences as hell strips. Salt, sand, radiating heat – along with the added occasional misfortune of cars, juvenile delinquents and shopping carts running into the trunk – are the major ones. The main differences between the two are that parking lots generally offer a bit more rooting space and a whole lot more interaction with pedestrians.
Middle of turf: Generally, trees and turf don’t mix. In most scenarios, turf requires more water and fertilizer than trees; in a mixed planting, if moderate amounts are applied to keep the turf thriving, excessive amounts of both are received by the trees. As well, in the midst of an island of turf, tree trunks are prone to mower blight, especially by youngsters and turf maintenance professionals who are in a hurry. The key message to deliver to them is to stop the movement of the mower before it reaches the tree, not after.
Next to concrete and rock: These materials have their place in the landscape, but it’s hard to overlook their negative impact on trees. They have a warming effect on the soil, don’t facilitate horizontal root growth as well as organic materials, provide no soil replenishment and are just so-so on moisture retention and weed suppression as compared with organic mulches and materials.
Compacted sites, high traffic spots: Settings where the soil particles are routinely compressed are tough locations for trees. Common locations for compaction of the soil are those that receive high traffic such as parks, campus grounds and shopping malls.
Adjacent to tough sites: Locations that are adjacent to the tough sites of compaction, hell strips, parking lots and other concrete surfaces may appear to be in good shape, or at least have the potential to produce healthy shoots and roots, however they are still adjoining and share a root zone. At best, sites adjacent to poor locations are half and half – half compromised and, hopefully, half conducive in terms of healthy soil, adequate space and overall growing conditions.
Close spacing: Often a scenario where the original property owner didn’t take size into account and planted way too many trees in way too small of a space. Close spacing is really an issue of trees competing for sun, nutrients and water.
Extremes of sunlight reflection: Commonly noticed when one side of a tree – the side that faces an office building – becomes blighted by excessive sunlight that can cause desiccation of the bark, stems and leaves.
Extreme shading: Opposite of sunlight reflection, absence of sunlight can cause etiolation, or a stretching for adequate light to support sturdy shoot growth. Growth that occurs in a heavily shaded location is usually thinner and weaker than when grown under ideal conditions.
So, what to do?
Identification and understanding is the first step in dealing with difficult sites; four other actions are next as making a difference in your landscape:
*First – it’s important to evaluate the status of the tree in question. Inspect for tree hazards and document defects that will influence future actions.
*Second – decide whether to keep the tree in the landscape or remove it. Consider the number of issues that weaken its structural integrity and limit the aesthetic value. If the tree doesn’t contribute toward the goals for the property, perhaps it shouldn’t remain on site.
*Third – if removal is chosen, possible replacement choices for each site can be contemplated. This is especially true for specimens that are not performing well due to an incompatibility with the size, sun, shade, soil and slope specifics of the site. For example, if a large tree is growing where a small one is called for, the potential replacements should be chosen from that group of options. In terms of possible selections for new specimens, local botanic gardens and arboretums are good places to gather information on suitability.
*Fourth – avoid planting in tough locations in the future. Seek advise on the microclimates where trees simply aren’t a good choice. In many scenarios, tall shrubs, groundcovers, perennials, native grasses and other landscape ornamentals are better options.
Often times, urban trees are vulnerable to pests and diseases because they are highly stressed. Stress can result from a variety of factors including the following:
-paved surfaces that interfere with water absorption
-restricted root spaces
-competition from dense layers of turf that surround a tree – Note: your trees should have layer of mulch surrounding diameter – call our Hometown Landscape division @ 301-490-5577 to assist with this recommendation.
Trees are also often times planted where they shouldn’t be or can be damaged from construction or heavy equipment. There is no single solution for managing all these issues; however, Hometown Tree Experts could assess this issue to ensure improving the overall health of your trees. Research has shown that proper care can increase the fine root density, helps to reduce water loss during dry and hot periods, and could increase the protective barrier of leaves. The trees are also greener and are better able to deal with stress. Call Hometown Tree Experts for solutions to your possible stress management @ 301-250-1033.
Sulfur dioxide, nitrogen oxides, particulate matter, fluorides, carbon dioxide, ozone. What do all of these hard-to-pronounce things have in common? They are all making their way into your body when you breathe. That’s right, these air pollutants are everywhere, even when you can’t see them. In cities, there’s a mouthful in every breath.
There are two types of air pollutants: primary and secondary. Primary pollutants are toxic as soon as they are released into the air and typically have a source that can be pinpointed. The biggest threats in this category in cities are particulate matter (PM), sulfur dioxide (SO2) and fluorides. Secondary pollutants, on the other hand, form in the air from interactions whose components might not have been toxic on their own. The major secondary pollutant we find in cities is ozone (O3).
When we talk about ozone as an air pollutant, we’re referring to ground-level ozone (which we don’t like) as opposed to stratospheric ozone (which we do like) that creates a layer in the atmosphere protecting us from UV rays. Ground-level ozone is common in areas with dense populations and traffic because ozone forms when hydrocarbons and nitrogen oxides (NOx) from industry and automobile emissions interact with sunlight.
Particulate matter consists of microscopic particles from car exhaust, road dust, industry and other emissions. It is usually measured in two categories according to size: PM10, the larger kinds, and PM2.5, the smaller and more dangerous. The smaller the particle, the deeper into your lungs it can travel, and once it’s down there, it stays there. This leads to respiratory illnesses like asthma and lung cancer — outdoor PM causes 3.2 million deaths every year worldwide. SO2 and fluorides are produced by fossil fuel combustion, which of course there’s a lot of in cities.
With the known health consequences of respiratory illness, cardiovascular disease, and lung cancer, it is clear that we should avoid exposure to these toxic air pollutants, but we don’t always have a choice. People in cities are especially vulnerable, since they have such frequent exposure to high concentrations of them. According to the World Health Organization, concentrations of PM exceed safe levels on the streets of more than 600 U.S. cities. Thankfully, city trees and greenery offer the beginnings of a solution to urban air pollution.
A study in London linked the annual removal of 90.4 tons of PM10 by urban trees to a decrease in 2 deaths and 2 hospitalizations per year. And according to a study in the U.S., the amount of PM2.5 removed annually by trees in 10 cities across the country in 2010 ranged from 4.7 tons in Syracuse to 64.5 tons in Atlanta. In the same cities, estimates of the annual monetary value of human health effects associated with PM2.5 removal, such as hospital admissions, respiratory symptoms and related deaths, ranged from $1.1 million in Syracuse to $60.1 million in New York City. That’s right: trees save lives and money.
Strategic placement of grass, ivy and other plants in cities can reduce the street level concentrations of NO2 and PM by 40 and 60 percent, respectively. There are multiple ways trees help to make urban air cleaner by filtering out pollutants:
Lowering temperatures reduces the movement of harmful ambient particles and prevents more pollutants from evaporating into the air. Trees create a great cooling effect by shading homes and streets, breaking up urban heat islands, and releasing water vapor into the air through their leaves. More tree crowns mean less dark surfaces like parking lots and paved streets being exposed to sunlight and emitting heat. Tree canopy cover in Los Angeles has decreased over the last 50 years, and a corresponding 6°F increase has been measured. Depending on the tree placement, trees can cool a city by up to 10°F, reducing the concentration of PM and other air pollutants with each degree.
Removal of pollutants
The first way trees remove air pollution is by particle interception: trapping pollution particles on their leaves and bark. Once the particle has been removed from the air, it is usually washed off the tree by rain or falls onto the ground with leaves and twigs. Studies have shown that in one urban park, tree cover removed 48 pounds of PM, 9 pounds of NO2, 6 pounds of SO2 and 100 pounds of carbon — daily. Silver birch trees in particular have been studied for their particle interception abilities: They have been found to reduce concentrations of PM by more than 50 percent.
A more complex way that trees filter the air is through gas uptake by leaf stomata. The stomata are tiny pores on tree leaves, and they absorb air to collect CO2 in order to perform photosynthesis. During that uptake of air, they also absorb gaseous pollutants in the air. Once inside the leaf, the gas diffuses throughout the leaf’s pores. It is then absorbed by films of water inside the leaf where it will either form acids or react with inner-leaf surfaces to become less toxic. It is estimated that one tree can absorb almost 10 pounds of polluted air through its leaf stomata every year.
Energy effects on buildings
Now that we understand trees’ chemical abilities, we can factor in their physical ones. Trees shade buildings in the summer and block winds in the winter, so it makes sense that they reduce building energy use for both heating and cooling purposes. Minimizing energy needs lowers the amount of fuel combustion necessary and therefore reduces the amount of pollution from power plants entering the air in the first place.
Once seen as an aesthetic window dressing, trees have never seemed as important in cities as they do now that we know their full potential. We can’t decide to stop breathing when we walk down a city street, but we can decide to plant and maintain healthy trees and hedges in cities to support the cause for greener cities. The air we breathe is a little bit cleaner thanks to each and every tree. Let’s keep it that way.
California’s magnificent Coast Redwood is the world’s tallest known tree and one of the world’s oldest trees. Average mature trees, several hundred years old, stand from 200 to 240 feet tall and have diameters of 10 to 15 feet, and some trees have been measured at more than 360 feet. The tallest tree in the world, The Stratosphere Giant located at Humboldt Redwoods State Park, is just over 370 feet tall. In the most favorable parts of their range, Coast Redwoods can live more than two thousand years.
Redwoods are named for the color of their bark and heartwood. The high tannin content of the wood gives the trees remarkable resistance to fungus diseases and insect infestations. The thick, fibrous bark has an even higher tannin content, and insulates them from the periodic fires which have occurred naturally down through the centuries in the redwood region.
These immense trees have delicate foliage. Narrow, sharp-pointed needles only one-half to three-quarters of an inch long grow flat along their stems, forming feathery sprays. Redwood cones are about an inch long and each cone contains 14 to 24 tiny seeds; a pound of redwood seeds would number more than a hundred thousand. Redwood seedlings grow rapidly, more than a foot per year in good conditions. Young trees also sprout from their parents’ roots, taking advantage of the established root system.
Coast Redwoods form almost pure stands in some areas, especially on flat, silt-covered river and creek plains such as the Bull Creek Flats area and the Rockefeller Forest. Coast Redwoods are also found in mixed evergreen forest with the majestic Douglas fir, as well as western hemlock, grand fir, and Sitka spruce. On drier slopes tan oak, madrone, maple, and California bay laurel grow along with the evergreens. Rhododendrons and a variety of ferns are the most common under story plants. Other plants which flourish under the trees in the duff of fallen needles include poison oak, huckleberry, hazel, and many flowering herbs.
Mammals found in the redwood forest include the ubiquitous raccoons and skunks, black bears, Roosevelt elk, deer, squirrels, porcupines, weasels, mink, and the rare ringtails. Among the birds found would be the marbled murrelet or the northern spotted owl, both of which nest almost exclusively in old-growth redwood and Douglas-fir forest. Many visitors in the redwoods notice a common mollusk, the yellow banana slug.
It is generally believed that the last ice age limited the Coast Redwoods to their present range, a narrow 450-mile strip along the Pacific Ocean from central California to southern Oregon. In the redwood belt, temperatures are moderate year-round, and heavy winter rains and dense summer fog provide the trees with the water they need. This climate was far more common in earlier eras. Paleobotanists have discovered fossil redwoods throughout what is now the western United States and Canada, and along the coasts of Europe and Asia. Some of these fossils are as much as 160 million years old. Redwoods are relatively recent arrivals in their current region; the earliest fossil record in California is found in rocks less than 20 million years old.
A natural Coast Redwood forest is a perfect recycling system. The soil (like that in any high-rainfall climate) contains few nutrients; most of the substance necessary for life is in the trees themselves, living and dead, and in the other plants and animals of the forest. If trees are removed from the forest instead of being allowed to die and decay naturally, many nutrients are lost from the cycle.
Welcome to the new Hometown Tree Experts website and blog. We will be updating the blog section from time to time to information you on some imprtant announcements and tips you can use.