Is that a tree or just a big weed?

Reexamining the purpose of a tree … in this case, it’s for showy flowers and fruits. (Photo: John C. Fech)

What’s the definition of a weed? The most common one is “a plant growing out of place in the landscape.” The most familiar weed in a landscape is a dandelion in the lawn, but just about any plant can be a weed if it’s inappropriately located or in poor condition. So, if a tree is too close to the foundation of a house, encroaching on the driveway, casting too much shade, competing with an important part of the lawn or continually infested or infected with various pests, perhaps it’s time for removal. Here’s a systematic approach for determining if a tree is a boon or bane.

Purpose of a tree

Determining if a particular tree is to be considered a weed begins with recalling its purpose. Is it to produce shade for a patio? To frame the house? For fall color/spring blooms? Or is it the all-too-often “front yard ornament” — a lollipop that is planted when the house was built? Knowing the answer to this basic question really helps. It’s the foundation that all future maintenance or new plantings are based on.

Once the original purpose is known, it should be reexamined to determine if it is still valid. For example, if the tree’s purpose was for shade on the deck and the deck is no longer there, or the current residents never go out on the deck due to being faced with too many mosquitos or a lack of interest, then perhaps the tree is no longer needed or at least not worthy of its presence in light of the problems that it may be causing (moss, surface roots, thin turf, disruption of the turf sprinkler pattern, etc.). If, however, the owners of the property really enjoy the deck and use it frequently, then it should be viewed as an asset, not a detriment.

Evaluating a tree’s location can help determine if it’s a detriment, as is the tree shown here. (Photo: John C. Fech)

Location

Next, consider the location. What part of the landscape is it situated in? Commonly, when planted by do-it-yourselfers, the location is an afterthought. The result is trees under power lines, next to the foundation, adjacent to a vegetable garden or driveway and maybe the worst of all, at least visually, smack dab in the middle of the front yard and in front of the front door.

One of the ways to ensure the proper placement is to embrace the concept of “separation of turf and ornamentals.” With the guiding influence of purpose in mind, trees can be placed in the landscape either in groups or singly without the co-location of turfgrass. The key to success is to start or revisit a bubble diagram, where each plant type (vegetables, fruits, turf, shrubs, trees, ground covers, perennials) are designated as planting masses in relation to each other. This approach limits problems with competition, excessive maintenance needs, shade and pests.

Size

The current and future sizes of a tree are important considerations. Again, a couple of questions help with classifying a specimen as a weed or valued plant. Is it too big for the location? Too small to do the job or accomplish the purpose? Commonly, the older neighborhoods of a city can take on the well-deserved reputation of “shade havens,” where the trees are large and the tree canopy is strong. This is a good thing in general, with the benefits of atmospheric cooling and carbon dioxide sequestration being realized; however, the size of the specimens carry with them potential for being too large for the landscape.

Planting large trees under power lines is a problem in the making. (Photo: John C. Fech)

When a tree is too large or too dense, we often see problems with excessive moss growth on roofs, droppage of small twigs and branches, high costs for tree maintenance and the lack of the option to grow sun-loving plants such as coneflowers, sedums, lilac, roses and yarrow underneath. Additionally, in tree-heavy sites, sun-adapted turf species such as Bermudagrass, zoysiagrass, buffalograss and Kentucky bluegrass simply won’t thrive, let alone survive. Even shade-tolerant turfs such as centipedegrass and tall fescue can struggle if they receive fewer than three hours of sun each day.

The flip side of the size issue is equally as important. If the purpose is to frame the house, newly planted deciduous trees simply aren’t going to fit the bill, especially if the property owners are impatient or if slow-growing species such as paperbark maple or ginkgo were planted.

Tree conditions

After the fact Trees planted as an afterthought near sidewalks often serve no purpose. (Photo: John C. Fech)

The health and vigor of the tree in question are crucial pieces of information used to decide whether a particular specimen is a weed. The list of possible defects is a long one. To name a few: decay, co-dominant leaders, cracks, basal/bole issues, previously cabled operations, leaning, root detachment from soil, stem girdling roots, deeply planted specimens, hanging branches, dead wood and heavy-duty/probably forever maladies such as chlorosis and emerald ash borers. In addition to the actual flaw, it’s important to consider the “target” or what the tree could fall on if it fails. People and valued property are the most common targets. If the site is one where frequent human activity takes place, such as a day care center, school or home residence, or the structure underneath or nearby the tree (new fence, house, neighbor’s pool) is highly valued, then the need for immediate action increases dramatically.

A thorough and honest assessment for each specimen should be conducted to determine if these concerns are present and, if so, to what degree. For most lawn care operators and landscape contractors, the best approach is to identify each potential problem and then consult with an International Society of Arboriculture Certified Arborist to validate the concern and assist with communicating the importance of action to the property owner. Finding one in your area is easy. Visit TreesAreGood.org/FindAnArborist.

Decay in a mature tree is a potential defect that should be inspected by an ISA-Certified Arborist. (Photo: John C. Fech)

Post-evaluation options

Once an expert opinion has been provided, a decision for appropriate tree care must be made. This usually falls into one of four categories:

• Monitoring: The “watch and wait” option is best suited for issues that are just starting or where no target is present.
• Pruning: A good choice where only one tree in a specific area is being treated, for species that close wounds readily and for specimens that are well situated and in good overall health.
• Pest control: It’s wise to choose this option for diseases and insects that can be controlled in a one- to three-year time frame, then implement a regular inspection regimen to detect reinfestation/reinfection.
• Removal: When the risks and concerns greatly outweigh the rewards and benefits, it’s time to remove a tree. Age, condition and location greatly influence this choice of action.

John C. Fech is a horticulturist with the University of Nebraska-Lincoln and certified arborist with the International Society of Arboriculture.