One of the primary recommendations when planting a tree is to create a protective area around it, a buffer zone, separating the tree from the lawn. Which is where many people plant a new tree, smack dab in the middle of an existing lawn. Creating that buffer zone keeps out-of-control lawn mowers and weed eaters away from that vulnerable trunk. It is also good not to have the competition of grass, weeds or other dense growth right up to the trunk for other reasons as well including holding moisture against the trunk inviting fungal activity and providing cover for voles to creep in and munch.
This buffer zone is often called a tree island. In a previous blog, The Benefits of a Tree Island, I explain why you would want to create one. This zone not only separates trees and companion plants from turf grass but can also buffer them from other landscape features, such as hardscape.
This area can be large but if that doesn’t suit you, it can be a small area. Creating this protective area is relatively easy and using the cardboard method described below precludes the need to use chemical herbicides.
If this is a fresh planting and you have bare soil, great; you can skip Step One. Otherwise, read on:
Step one – If you have grass or existing weeds, scalp them as close to the ground as possible (without damaging the existing tree trunk). You can use a weed-eater if you stay well away from the tree. It is recommended you first create a buffer by hand-clipping or pulling any unwanted growth to a safe distance away from the trunk. Then scalp the rest of the desired area with whatever implement you have.
Step two – Thoroughly water the soil. Soil should be moist at least 2″ deep…not saturated, but moist.
Step three – Cover the area with a layer of cardboard starting at least a couple of inches away from the trunk. Slightly overlap the seams (if you leave gaps, you will have nice, tidy rows of weeds or grass). Thoroughly water the cardboard. If needed, you can secure the cardboard with landscape staples.
Step four – Top dress with your preferred organic mulch starting at least a couple of inches away from the trunk. Keep the mulch to a very thin layer at that starting point increasing it to a 2″ depth as you get further away from the trunk. You do not want to build up anything near the base of the tree. This is an area which should be allowed to dry out, not kept moist. And notice I said organic mulch. You want the benefits of decomposing matter to go into the soil.
This process will help control weeds for approximately 2 to 3 years in my experience. However, length of efficacy definitely varies depending on climate and the type and density of unwanted growth you are trying to suppress.
The cardboard will decompose in this time and you will have to replace it. However, in my opinion, this beats constant pulling of weeds and/or grass. And the decomposition process benefits the soil, worms and other soil organisms, turning this entire process into a multi-beneficial one.
There are probably as many different definitions for an urban forest as there are people you ask. One definition on the internet stated simply it was a densely wooded area located in a city. Hmmmm, well. Do they mean a remnant of an original forest? Or are they talking about a planted park? Do these two features alone define an urban forest? What about those cities without remnant forests that claim to have an urban forest? I am picturing the cities that have grown out of the Great Plains which was prairie with barely a tree in sight.
Another definition I came across comes from Wikipedia: “An urban forest is a forest or a collection of trees that grow within a city, town or a suburb. In a wider sense it may include any kind of woody plant vegetation growing in and around human settlements.” (I like this a bit more.)
Then a quote from the forest service website: “Over 130 million acres of America’s forests are located right in our cities and towns. Urban forests come in many different shapes and sizes. They include urban parks, street trees, landscaped boulevards, gardens, river and costal promenades, greenways, river corridors, wetlands, nature preserves, shelter belts of trees and working trees at former industrial sites.” Alright! Now, we’re talkin’!
I did find it interesting they specifically included “working trees at former industrial sites”. Actually, you could say all trees “work”. They are cleaning our air, replenishing oxygen into the atmosphere, taking in carbon dioxide, sequestering carbon, cooling our homes and streets, providing wildlife habitat, providing shade for those picnics and summer time festivals. They are mitigating storm runoff, reducing the heat island effect, and attenuating noise. They offer shelter and protection against wind. They provide recreational venues and the opportunity to find peace and tranquility in a hike.
If there are any of the above attributes you feel are undeserved, consider that not all trees perform the same functions in a like manner. Some trees have been misplaced (by us) which could minimize their abilities. Some are so mismanaged by us, they can offer only a mere shadow of their full potential. None of these circumstances are their fault but more often stem from our errors.
An urban forest is not comprised merely of the street and park trees owned or controlled by a municipality. But, in my opinion, encompasses every plant in any built environment ranging from residential, semi-rural, exurban, suburban to the hardcore urban centers. And it doesn’t matter where they are planted. They might be located in a park, in boulevards, a private garden, downtown shopping malls, rooftop gardens, potted plants. They all count.
Notice I said “every plant”. If I were writing the definition, I would enlarge it to include every photosynthesizing organism. So we would include turf grass, annual and perennial flowers, herbaceous and woody shrubs as well as our long-lived, perennial trees. If managed properly, they all contribute to a healthier environment….because they ALL photosynthesize.
Photosynthesis is one of the two most important energy-related processes in the world, the other being cellular respiration. (See my blog Understanding Photosynthesis, which actually should be retitled to Understanding the Importance of Photosynthesis.)
If you live in a city that has an Urban Forest Management Plan, you may have seen or read the information on species inventory and the benefits these trees give back to the community. These inventories generally only tally the municipally-controlled trees and do not include those in the private sector which could easily double the number of trees and, therefore, the benefits provided.
There are many wonderful tree species in the world. Far too many to rate or designate as to which ones are “the best”. Because “the best” becomes relative to area, site and personal preference: “Beauty is in the eyes of the beholder.”
Unfortunately, it is not uncommon to hear someone refer to a tree as a “trash” or “weed’ tree, implying it has no value. Sometimes this is in reference to a native tree that grows prolifically but doesn’t necessarily have a long lifespan, such as some alders, Alnus spp, or the water birch, Betula occidentalis, both common in riparian areas. But ecologically, they perform important functions. In addition, they can be beautiful additions to a naturalized landscape.
Sometimes the reference is to a non-native species commonly planted in the past which has proven to be less than ideal in the present. The silver maple, Acer saccharinum, and Siberian elm, Ulmus pumila, are examples. But a tree suitable for Zone 2, as is the Siberian elm, has a place in difficult-to-grow climates. And frankly, it is not the tree’s fault when planted in an area with a milder climate where they grow rapidly, seed prolifically and are often, in my humble opinion, managed poorly. This is often the case with both the silver maple and the Siberian elm. Planted suitably and managed properly both of these species can be assets to a property.
Many people do not live in areas where a luxurious climate offers an abundant diversity of species from which to select. When your options are limited, then each and every tree has a place and purpose and can and should include both native and non-native species if we are to achieve recommended diversity for long-lived sustainable urban forests.
Some species have acquired a “bad rep” due to fast but weak growth, potentially invasive qualities in their introduced home, production of substances which have proven problematical to people with allergies and now appear on banned lists in some areas. These are, for the most part, justified for specific areas but these condemnations should not be construed as limiting criteria everywhere.
The box elder is a fast-growing tree in the maple family with a large native range here in North America. It is considered by many to be a “weed” tree. However, if you are in a challenging environment, this tough tree may be the perfect answer to a resilient shade tree.
The importance for understanding how you use a product is due to the potential ramifications of the application. A soil amendment typically refers to a product intended to be incorporated into the soil, and therefore, is generally well-decomposed. A top dressing generally refers to a product which will be laid on top of the soil and, therefore, may not be well-decomposed if at all.
Since those ramifications can be pretty extreme, you need to have a clear idea of your desired goal prior to making a final decision on the product you select.
Top dressing garden beds and/or around trees is an excellent idea for many reasons, not the least of which the benefits it gives to the soil. Bare soil is subject to degradation in many forms: wind and water erosion, compaction from rain and irrigation, soil microbes die off in barren soil, the soil can heat up enough to damage roots. For more details, refer to my blog Benefits of Tree Islands
Nature doesn’t like a vacuum; if there is an empty space, an organism is going to try to fill it up as soon as possible. Weeds love bare soil; they are the ultimate pioneer species. those are the species which come in and colonize abandoned, disturbed, or bare sites and can thrive in adverse conditions.
Top dressing is a product you apply to the surface of the soil for a variety of reasons including (but not limited to): moisture retention, temperature moderation, erosion control from wind and/or rain, reduction of crusting due to rain and/or sprinklers, weed suppression, slow incorporation of organic matter facilitated by soil organisms, slow release of nutrients made plant available by soil organisms.
I am not a fan of using inorganic products such as pea gravel and rocks around trees and shrubs. The above list of benefits is best achieved when using organic products.
Organic products used as top dressing may have a high carbon-to-nitrogen ratio (C:N) as they are not well-decomposed. this generally means the ratio is 25:1 or higher. It takes longer to break down and provides a slow incorporation of organic matter to the soil as worms and other soil organisms process it. Common products include pine needles, bark chips, cardboard, or whole tree chips.
Whole tree chips refer to all components of a tree: leaves, twigs, wood and bark. We, personally, prefer whole tree chips because they have more of the components utilized by trees rather than just a single component.
If you are using top dressing to create a tree island, a flower bed or pathway, the goal might be weed suppression as well as other benefits and, in that case, using a product with a high C:N ratio which will take longer to break down is a good choice.
You certainly may use a partially or well-decomposed product as a top dressing but it may not achieve your desired goals if weed suppression is one of them. Well-decomposed product is already a growing medium (which is what makes it suitable to incorporate into the soil).
For more detail on why you don’t want to use a product with a high C:N ratio as an amendment which will be incorporated into the soil, please refer to my blog Will Adding Mulch Tie Up Nitrogen in the Soil?
Soil amendments are products you wish to incorporate INTO the soil. The reasons might be to increase the organic matter content sooner rather than later. Soil organic matter (SOM) is vastly important to the health of the soil, the soil organisms and the plants growing in the soil. It positively influences or modifies virtually all soil properties, including but certainly not limited to improvement in infiltration and percolation of water, increased nutrient exchange capacity, water-holding capacity and aeration. Amendments should have a C:N ratio of no more than 24:1. This may be a product you purchase or a compost made in your backyard.
Whether you are purchasing an amendment or have made the compost yourself, double check it is in fact well-decomposed prior to digging in. Criteria generally cited for “well-decomposed” are: it should smell “good”, be dark brown and crumbly.
The “good” smell is that wonderful earthy smell. It should not smell stale or like rotten eggs. This would indicate it is not thoroughly composted, is anaerobic or has other serious issues you don’t want.
The dark brown coloration is indicative of decomposed organic matter. The texture of the product should crumble readily; in fact, you should not be able to discern its origin.
If the product does not meet all of these criteria, I would hesitate to incorporate it into the soil. If it smells good but still has hard pieces in it, you can use it for top dressing, letting it decompose more fully on site.
© 2018 McNeill’s Tree Service
Plant Health Care (PHC) is a term often denoting a service offered by companies in the green industry indicating the company offers a comprehensive program to manage the health, structure and appearance of plants in the landscape. If they don’t offer an aspect of the program, they generally will be able to advise you on what is needed and offer referrals to a company that can supply that need or resources you can look into if the care can be managed by the homeowner.
A component of PHC is Integrated Pest Management (IPM) which is the diagnosis, monitoring and application of the least toxic choice in dealing with plant pests.
Natural and applied methods are considered in IPM. Natural methods are environmental events which will stop the progression of the problem, such as a change in the weather that was conducive for a specific disease. An example being a disease pathogen may thrive in moist, cool conditions; the weather gets hot and dry, the disease progression ceases. If this can be anticipated, it will affect the choice of whether to apply any other method or let nature handle the situation.
Applied methods are ones we have to implement. They include cultural, biological, mechanical controls with chemical control being used as a last resort.
We can’t eradicate all pathogens or pests from the environment. It isn’t practical nor is it desirable. IPM recognizes the need for a certain number of “prey” insects the “predatory” insects will feed on. Many diseases are endemic to an area and only become problematic given the suitable environment and the host species.
Whether the problem is insects or a disease, it is crucial to correct any cultural practice that may be contributing to the problem. Without doing so, it is pointless to apply any pesticides. Therefore, cultural controls are a first step in PHC/IPM programs.
If available, plant resistant species for diseases known to be prevalent in your area. A classic example is dealing with fireblight, a bacterial disease potentially devastating to members of Rosaceae. Numerous cultivars of Malus spp, apples and crabapples, have been developed for resistance to fireblight as well as apple scab, powdery mildew and rust diseases. Combining best management practices and planting resistant trees may significantly reduce or even eliminate the need for chemical application.
Landscape management practices may inadvertently contribute to establishing a suitable environment for diseases or creating a succulent smorgasbord for insects. An all-too-common example includes over-fertilization. Many articles, websites and well-meaning professionals advise the application of nitrogen as well as other plant nutrients in quantities exceeding plant need.
Excess nitrogen pushes vegetative growth at the expense of root development, storage and defense. This succulent vegetation is highly attractive to many destructive insects and nitrogen virtually feeds many pathogens causing diseases to be more virulent and prevalent. Examples include Armillaria root rot, fireblight, fusarium, phytophthora, powdery mildew, pseudomonas and rust diseases.
Weed and feed products commonly sold for lawn care maintenance have herbicides in them that are designed to manage broad leaf weeds. Trees, shrubs and many flowers are broad leaf species and are susceptible to these herbicides as well. If weed control is desired in turf grass, it is far better to discretely spot treat if populations are beyond controlling by hand.
Another cultural practice that influences the suitable environment is inappropriate watering. Too much and you will be suffocating roots creating a suitable environment for root rot diseases. Too little and you will weaken tree defenses making the plant more susceptible to opportunistic pathogens on weakened tissue as well as attracting some of the most damaging insects, the borers, who are drawn to drought-stressed trees.
Mowing and weed eating are often maintenance practices which cause physical damage to trees leaving wounds that become infection courts for both pathogens and insects. (See my blog Can A Weed Eater Really Kill A Tree?) Creating a protection zone (no-mow zone) around the trees, at least in a minimal mulched area if not a full tree island, will eliminate these man-caused injuries. (See my blog Benefits of a Tree Island)
These are a few examples of cultural practices which should be evaluated and altered as needed.
Nature has provided many organisms which combat diseases and insects. In a balanced, natural setting these may be sufficient to keep damaging agents at an acceptable level. However, in our built environment, they may not be able to keep up with the task. It may be desirable to release biological organisms when they are not in sufficient numbers. Examples of these would be some of the bacteria, e.g.., Bacillus subtilis, that combat diseases such as fusarium and phytophthora or bacteria, e.g., Bacillus thuringiensis, that control numerous insect species.
Biological control may also include the release of predatory insects to control pests, such as lady beetles and green lacewings which are both voracious eaters of aphids. A side note: if purchasing these beneficial insects, lady beetles will be more effective in a closed environment such as a greenhouse unless there is sufficient food and water immediately available. Green lacewings may be a better choice in an open-air landscape.
Mechanical or physical controls
Physical manipulation or creating an obstruction to protect plants can be very simple and effective. Examples would be fencing your tree to keep deer from browsing and rubbing or protecting the trunk of a tree to keep the neighborhood cat from using it as a scratching post.
Chemical pesticides are kept as a last resort rather than a first so we have a place to take a final stand. With that said, there are some pests that have been identified as requiring the hammer approach first and last, just not nearly as often as some think. There is also a vast array of chemical pesticides to use including low toxic, organic, inorganic and synthetic products. Wading through the plethora of products is daunting and confusing. Trying to make sense of the labels can be just as daunting and confusing. It is strongly urged to consult a professional applicator prior to applying any pesticide yourself.
Broad spectrum cover sprays, sprayed over the entire property (plant population), will inevitably harm or reduce the number of naturally occurring beneficial and predatory organisms. These are the ones that can keep injurious pests under control and should be protected as much as possible.
Many pests are not damaging to long term plant health. Many pests are a nuisance to us more than they are a problem to the plants. And some need an aggressive approach. A good PHC technician should be able to help you wade through the potentials and come up with a game plan that will address the issues, causing as little negative impact to as many beneficial organisms in the environment as possible.
Biotic refers to “living” as opposed to non-living which is referred to as abiotic. Biotic diseases are pathogenic, infectious and can spread from plant-to-plant, generally of the same species. They are caused by organisms such as fungi, bacteria, viruses, nematodes and mycoplasma-like organisms (MLOs). (Please don’t ask me to explain MLOs.) Fungal diseases are the most common but Iwant to stress that not all fungi cause diseases. Most organisms are necessary and vital constituents in our environment.
When clients call about a problem with their trees or other plants, they often do not know whether it is an insect or disease issue and many times do not consider abiotic issues at all. However, many diseases actually stem from abiotic disorders as pathogens take advantage of a weakened or damaged plant.
Diseases require three circumstances in order to develop: 1) A pathogen has to be present, 2) a susceptible host has to be available and 3) the suitable environment has to exist. If any one of those criteria is not present, the disease will not develop. This is called the disease triangle.
Many organisms exist in a non-pathogenic state performing necessary functions in the environment, only becoming pathogenic when a susceptible host and suitable environment coincide. Trying to manage diseases by eradicating the pathogen is seldom (if ever) feasible or even desirable. Instead, reduce the potential of a susceptible host or disrupt the suitable environment.
A plant with susceptibility to a disease becomes the host when the pathogen and suitable environment are present. A number of plants have been specifically developed to resist common diseases. Determine what are common and damaging diseases in your area and search out resistant cultivars of plants.
An example would be many apple and crabapple trees are susceptible to four primary diseases: fire blight, apple scab, powdery mildew and rust diseases. There have been many cultivars of these popular plants developed with varying degrees of resistance to one or all of these common diseases. Instead of fighting a likely problem, minimize the potential by selecting one of these resistant cultivars.
A suitable environment is when the temperature and moisture are conducive for disease development. And it varies from disease-to-disease. We are somewhat at the mercy of Mother Nature here. Cool, wet springs are going to be very suitable for certain diseases such as anthracnose.
Many diseases are spread by wind and/or rain. However, when you consider that water, not just in the form of rain, but irrigation practices as well, can create a suitable environment, then managing irrigation practices may go a long way to minimizing the potential for diseases being able to dock.
Knowing a disease’s life cycle may give a clue as to whether you should overhead water or not. Some diseases are dispersed by rain or splashing water and, therefore, you would want to avoid overhead sprinklers. However, some, for example powdery mildew, do not dock on wet surfaces. In that case, overhead watering susceptible plants, such as bee balm, Monarda spp, and crabapple trees, Malus spp, may be a good idea. (Note: there are actually a tremendous number of plants susceptible to powdery mildew). You need to know when the appropriate time of day to overhead water….and that may vary area to area. Here in Western Montana, I have been successful at controlling powdery mildew by overhead watering in the early afternoon. This timing may not work for you. Note: if a plant susceptible to powdery mildew is surrounded by plants susceptible to other fungal diseases that are enhanced by overhead watering, well, you have to pick your battles.
Some fungal pathogens thrive in a crowded environment which blocks air flow. Judicious pruning that opens up the canopy may reduce the likelihood of the pathogen developing.
Pruning out diseased portions of a plant is often very effective at controlling certain diseases. It is recommended to dispose of the debris off site. It is also often recommended to prune fungal or bacterial diseased tissue from a plant during a dry period.
Determining the most likely pathogens in your area, the environmental conditions under which they thrive and their life cycle combined with an inventory of your species listing their individual susceptibilities will go a long way in helping you devise a plan allowing you to minimize potential problems. Nipping the problem in the bud….so to speak.
Abiotic refers to “non-living” as opposed to biotic (living). An abiotic disorder is a plant malfunction caused by non-living, environmental or human-made agents. Yes, humans are living but generally the implements they wield which harm trees are not: e.g., lawn mowers, weed eaters, vehicles, herbicides. Another criterion that defines abiotic is they are not infectious. Animal damage is listed under abiotic as the damage they cause is not pathogenic or infectious. (I know, life gets confusing.)
When clients call about a problem with their trees or other plants, they often do not consider abiotic possibilities, rather assuming the problem stems from insects or disease. The reality is the vast majority of time, the problem is abiotic in nature or stemmed from an abiotic injury.
Environmental extremes are beyond our control: e.g., lightning, heavy snow and wind. Damage caused by these agents should be assessed for prognosis of safety and survival and a management plan devised. Is the damage significant? Can it be rectified? Will the tree survive? Does it pose a safety issue due to proximity to infrastructure or human proximity?
Activities which cause abiotic injuries we can influence involve common practices in managing our landscapes.
Lawn mowers and weed eaters can be deadly weapons to trees. My blog, Can My Weed Eater Really Kill a Tree, goes in to this implement in detail. Lawn mower damage from constantly striking the tree trunk close to the ground is also a common agent of creating an infection court allowing diseases to gang a toehold but can result in progressive decline even without a disease. It is easy to discount incidental contact with a tree, thinking “it can’t be that bad”. But it can and it is.
Another lawn care practice potentially damaging to trees that many don’t consider is the application of herbicides in controlling broadleaf weeds.
Many fertilizer products are listed as “weed and feed”, meaning they contain an herbicide in them as well as a fertilizer. This is supposed to address those pesky dandelions and other weeds in lawns. However, trees, shrubs and many perennials and annuals are broadleaf species as well. And in the case of trees and shrubs, their root systems may be occupying the same soil space as the lawn. What is applied to one affects the other. This is why we recommend creating tree islands or mulched areas around trees. (See my blog, The Benefits of a Tree Island)
Tying strings, garden hoses, installing swings or laundry lines by wrapping chains or line around limbs are another practice that may cause serious injury to a tree.
This includes staking for stability after planting and the tags that come with the tree from the nursery. Limbs grow, but strings, lines, ropes and chains don’t. The tree grows around them often resulting in constricting the vascular system of the branch, stem or trunk.
And then we have irrigation practices. It is easy to get into a rhythm of watering without really checking to see if the plants are being appropriately watered. Consequently, it is all too common to see over- or under-watered plants. One size does not fit all. And, yes I am going to say it again, trees grow. As they get bigger, their water requirements increase. Not only that, but if you have a sprinkler system that was set up when they were first planted, the system needs to be moved away from the trunk.
The roots are far away from the trunk and that is where the water needs to be applied. That growing trunk and buttress roots can also pinch off the water lines entirely.
Trees should be protected from animal damage before it happens. Waiting until you see the damage is too late. Some trees will stay vulnerable to animal damage their entire life and you need to make the decision whether you want to deal with that kind of commitment or pick a tougher species.
Planting herbaceous barriers to discourage browsing from larger animals may work but can backfire as they provide protection for rodents from natural predators.
There are many products to discourage browsing by deer. I have had good luck with liquid products as well as hanging bits of Irish Spring soap from target trees. You may need to experiment to see what will be effective in your area. However, if you are in a particularly heavy use area, fencing might be your only reliable recourse. You can be as creative and decorative as you wish, or keep it simple but effective, combining form and function. Works very well.
The answer to this frequently asked question, as with most questions pertaining to arboriculture, begins with the phrase “It depends…”
The short answer would be “If they need it.” Then a follow up question, of course, is “How do I know if they need it?”.
If you live in an area where the ground does not freeze and you have not had any precipitation, then your trees may very well need a drink or two in the winter.
If you are in an area where the ground does not freeze and you are getting regular moisture, then you probably do not need to water your trees.
If you are in an area where the soil DOES freeze and you are not getting any precipitation...well, if the ground is frozen it will do no good to create an ice rink around your tree.
If you are in an area where the soil freezes and you have snow on the ground, you don’t need to water.
If you are in an area where the soil freezes but you have periodic thaws, if you have snow on the ground you do not need to water…the melting snow will take care of it.
If you are in an area where the soil freezes and you have periodic thaws but no snow on the ground then check the melted soil….is it muddy? You don’t need to water. Is it dry? You do need to water.
© 2018 McNeill’s Tree Service
The decision to select native plants versus non-native plants is a personal one. There is no one right answer. There are appropriate species within each category and inappropriate ones as well.
There is a misconception that all native plants are more drought tolerant than introduced or non-native plants. That depends on the species. It is a statement you cannot take across the board. There will be exceptions in both directions.
Plants need water. Different species require different amounts of water. Some can go for longer periods of time without water than others. But a general premise is: trees grow where there is adequate water for their needs. Here in the Bitterroot Valley of Western Montana, native trees will be found along creek and river beds or in the mountains along drainages where water is more plentiful. The native plants surviving further from water sources are drought-tolerant species such as juniper, Juniperus scopulorum, sagebrush, Artemisia spp, rabbitbrush, Ericameria spp, as well as various grasses and forbs of high plains semi-arid environments. An unfortunate reality is many of our native species are not necessarily suitable for a managed landscape.
People living in areas with abundant rainfall and moderate climates have a plant palette consisting of a large selection of native species. This may enable the homeowner or landscape designer to stay within the native range and still create an interesting and diverse landscape. Those living in dryer and/or colder zones with limited species are going to have a harder time.
Here is, in my opinion, the caveat few take into consideration: there is arguably no species native to the built environment. Once we move into an area and alter the surroundings with hardscape, compacting the soil, bringing in fill from other areas, changing topography, the plants originally “native” to that site are no longer. Or probably a better way of saying it is the site is no longer suitable for that native species.
Then there are people with a flexible definition of “native”. For example, some broaden the limitations from their state to include any species native to North America. To my mind, if they are willing to use an introduced species from across the continent, Canada and Mexico (and then if you want to use the United Nations designation, add the Caribbean as well), why limit yourself?
Trading and exchanging seeds and plants has a very, very long history going back thousands of years. As global trade escalates, so do the pluses and minuses from those transactions. There are many beautiful, exciting plants to enjoy in our landscapes. And, yes, many we should be cautious of. However, non-native is not synonymous with invasive. That is another topic entirely.
Photosynthesis is the process whereby plants fix carbon dioxide (CO2) from the atmosphere, combined with water molecules (H2O), they utilize light energy (the sun) and convert it to chemical energy to produce organic compounds (C6H12O6) releasing oxygen (O2) into the atmosphere. Most references simply call the organic compounds sugar and, yes, the formula is a broad formula for glucose. However, I believe just saying “sugar” leads people to picture a sack of refined sugar you buy in the store. Plants do not produce highly refined, white sugar. But I digress.
Most descriptions of photosynthesis stop there emphasizing the benefits plants give us by releasing O2. After all, that is what we need to breathe. Maybe you are wondering what else can be said.
The thing is, the cycle doesn’t stop there. Please read on.
Recap: Plants fix CO2, combined with H2O they utilize light energy and convert it to chemical energy to produce organic compounds and O2. Now, here we go…
Plants utilize the organic compounds in structural growth, store some for future resources and use them for other regulatory processes. It (the plant) also exudes a portion of these organic compounds through the roots into the soil to be utilized by soil organisms for energy and food.
Organic matter (OM) builds in the soil as plants and soil organisms die. Microbes process the OM releasing plant available nutrients as they do so. As soil organisms die, more plant available nutrients are released. While all this digesting and processing is taking place, plants and organisms respire. Respiration is essentially the opposite of photosynthesis in that they utilize oxygen and exude carbon dioxide into the soil for release back into the atmosphere where it is taken up by plants once again.
This cycle is part of the soil’s self-regenerative capability and is, in fact, mandatory to all life on Earth.
Reality check: We need plants, but they do NOT need us! They created the atmosphere that enables us to exist. They are in essence environment builders.