The Informed Gardener: some terminology & current opinions about plants

If you’re new to gardening, you might think that gardening is simply about growing lovely flowers and veggies but in reality there are many different opinions about plants and gardening methods, and there are a variety of hotly debated environmental issues and social justice issues that tie into gardening. Many gardeners are completely unaware of these issues, so I’ve put together a small list of terms and concepts I have encountered more and more in the last few years:

Native vs. Non-native Plants

Native Plant: A plant that has evolved in a given place over a period of time sufficient to develop complex and essential relationships with the physical environment and other organisms in a given ecological community.

(definition from ‘The Living Landscape’ by Rick Darke and Doug Tallamy p.93)

Native plants have evolved in the same locations for a long time and they have adapted to particular soil and climate conditions. They have also co-evolved with the animals in those particular locations. Some animals depend completely on one type of plant and are known as specialists; Monarch butterflies are an example of this since they require milkweed plants for their caterpillars to feed on. Other animals are generalists and can get by on a variety of plants. Here in the United States, a plant is considered native if it was present in the landscape before European settlers arrived.

Non-native plants originated in other countries and were imported to the united States at different points in history. Unfortunately, the vast majority of plant nurseries grow mostly non-native plants and most garden centers including big box stores like Home Depot carry mostly non-native plants. You will find lots of Japanese trees (maple, cherry, etc) and Chinese flowers (astilbe, daylilies, etc) and other non-natives like tulips and hostas at any plant nursery. One big plus of non-native plants is that they often don’t have “pest” issues because native insects often have no interest in them; this is great if you’re not concerned about foodwebs or wildlife. Another reason they are so popular is because landscape designers use them a lot and they are ubiquitous. Of course, many non-native plants are beautiful and colorful as well so if your main concerns are color and form, then these plants are very alluring. Non-native plants are the mainstream and what people are usually talking about in gardening forums.

Fifteen years ago, University of Delaware Professor Doug Tallamy published a book titled ‘Bringing Nature Home’ in which he laid out a case against non-native plants. Tallamy’s research had shown that non-native plants, non-native trees in particular, provided little to no benefit to birds because they didn’t support the number of insects needed by birds to raise their young. He compared the number of caterpillar species found on an oak tree (500+) to those found on a Chinese gingko tree (5) and linked the decline in birds to the widespread use of non-native trees in urban and suburban landscapes. Tallamy’s work has raised awareness about the environmental impact of non-native plants and there is currently a growing trend of incorporating native plants into the landscape to assist wildlife, but there are other reasons as well: native plants use less water and require less maintenance once established, and they attract the beneficial insects that keep our backyards and veggie gardens free from pests.

Invasive vs. Aggressive Plants

An “invasive species” is defined as a species that is non-native (or alien) to the ecosystem under consideration; and, whose introduction causes or is likely to cause economic or environmental harm or harm to human health.

Source: U.S Forest Service

Within the realm of Non-native plants, there exists the concept of invasive plants or NNI (Non-native Invasives). These plants grow prolifically in an area and quickly displace the native plants in that area or cause harm to existing plants. Some examples of invasive plants are oriental bittersweet (celastrus orbiculatus), Japanese knotweed (fallopia japonica) and English Ivy (hedera helix). If left unchecked, English Ivy can climb onto trees and cause all kinds of problems that ultimately damage the tree. Another invasive plant is Tree of Heaven (Ailanthus Altissima), a tree native to China that grows quickly, has virtually no insect or disease issues and emits toxic substances in the soil that inhibits the growth of other plants around it. This plant also sends up shoots whenever the parent plant is injured so it is a real nightmare. The biggest concern with this tree at the moment is that it serves as a host of the spotted lantern fly, a destructive pest that is decimating native trees across the USA. The worst thing about NNIs is that some of them are sold in big box stores and uninformed nurseries so people have no idea that they are about to plant a headache for themselves or their neighbors. Visit the USDA website to view lists of invasive and noxious plants.

Some native plants also have the ability to spread rapidly but they are considered aggressive and not invasive since they are supposed to be where they are and are not an introduced species. I refer to these plants as bully plants and these are usually suckering type plants that form thickets or plants that produce a ton of seeds. Even if they take over an area, they still provide benefits to wildlife so they do not compare to NNIs, although they can be annoying. I have decided not to allow more than one evening primrose plant to grow in my small garden this year because last year it completely took over and it has already reseeded itself in early spring when most plants are still dormant, so it is definitely a prolific spreader. Some native plants are also classified as noxious because they contain toxic substances that can cause harm to people or animals. Some examples of noxious native plants are poison ivy and poison sumac. The complete list of noxious plants can be found on the USDA website.

Chemical Control vs. Mechanical Control

Mechanical control: a physical activity that inhibits unwanted plant growth.

Source: Wikipedia

NNIs are a big problem and all you have to do is visit your local park or botanical garden to see common invasive plants in action. Many park systems and botanical gardens simply do not have the manpower to deal with huge infestations of Japanese knotweed, kudzu or any other invasive plant. This brings up another hotly debated issue: whether herbicides should be used in restoration projects or at all!

I tend to shy away from chemicals and I have heard a lot of bad things about glyphosate (AKA Roundup) and other herbicides but I recognize that there are situations in which a targeted application of herbicide can be beneficial. Discovering tree-of-heaven in my yard and seeing how invasive it can be has softened my stance on herbicides. In fact, I plan to use herbicide on these trees in the fall instead of continuing to pull them or cut them, which has made the problem worse over the years. I sympathize with people working with acres of NNIs because in that case mechanical control is next to impossible. Mechanical control means hand pulling, digging up roots, smothering with cardboard, solarizing with plastic, practicing controlled burns, and doing anything else besides spraying chemicals that removes a plant. I believe that herbicide use has been marketed to such a degree that many people with small gardens are out there spraying everything willy-nilly without any concern at all about pollinators like bees and ants, and soil microbes. There is too much focus on eradicating small numbers of harmless “weeds” and this is like using a fire extinguisher to blow out a birthday candle. You don’t need to pull out the “big guns” for minor problems, most of the time mechanical solutions will do, but it’s not realistic to be 100% against herbicides, especially if we’re talking about park land, forests, and other large scale areas. Also, particularly nasty NNIs like Tree of Heaven and Japanese Knotweed are very difficult to eradicate without herbicide.

It is worth remembering that many native bees and other beneficial insects nest in the ground, so herbicides should not be sprayed all over the place. Ideally, herbicide should be brushed onto a stump or applied very close to the target plant. Follow bottle recommendations about when an herbicide should be applied (prebloom, etc) and what time of the day or season is best. Click here for more information about responsible herbicide and pesticide use.

TIP: Don’t assume that “natural” or “organic” pesticides like neem oil and essential oil blends are safe for bees and other wildlife. They may be better for the environment but they can still be toxic to beneficial insects. Look up the ingredients and follow instructions and recommendations for use.

Other Issues People Are Talking About Right Now:

Integrated Pest Management (IPM) is an effective and environmentally sensitive approach to pest management that relies on a combination of common-sense practices. IPM programs use current, comprehensive information on the life cycles of pests and their interaction with the environment. This information, in combination with available pest control methods, is used to manage pest damage by the most economical means, and with the least possible hazard to people, property, and the environment.

Source: EPA

Mosquito Spraying:

Mosquitoes, everybody hates them, but some people hate the mosquito spraying services hired by their neighbors even more. The problem is that the mosquito spraying companies use EPA approved pesticides like Pyrethroids that are actually harmful to bees and other insects, and the spray can drift to nearby properties and potentially kill beneficial creatures. Some of these pesticides are designed to leave a residue on surfaces and plants that kills insects on contact for a period of time after the initial spraying. This means many other unintended targets of mosquito spraying will be poisoned and killed for weeks or months. This is almost as bad as installing a bug zapper outdoors and zapping harmless moths and other creatures in an attempt to kill mosquitoes. Many counties have adopted an IPM strategy and have their own spraying programs, which means hiring a spraying service may be unnecessary. To see what your state and county is doing in terms of mosquito control, click here.

Some alternative approaches to hiring a mosquito spraying service (some of which are examples of Integrated Pest Management (IPM):

• Dump out pooled water and do not allow water to collect anywhere unless you have a pump running. Mosquitos lay their eggs in stagnant water.
• Doug Tallamy recommends filling a small bucket with water and grass clipping and adding a mosquito dunk in there. This way mosquitos lay eggs in the water but the larvae are killed before they can become mosquitoes.
• Try a Skeet-o-Trap or something similar that allows mosquitos to lay their eggs in it but has a fine mesh that prevents the larvae from exiting the trap.
• Run a fan outdoors. Mosquitos can be temporarily blown away from an area. This strategy is handy during a summer BBQ or outdoor event.
• Plant lots of mint and citronella; citronella candles are somewhat helpful.
• If you have the space, encourage bats by installing a bat house on a tree and planting night blooming flowers. Click here for more info about encouraging bats.

Leafblowers:

There was a time when leaf blowers were used to blow leaves into a pile for easy pick up but these days leaf blowers are being used for everything from cleaning debris off the street to cleaning dust off of vehicles to removing snow to repelling tear gas at a protest. Except for that last one, which happened during a very specific moment in time, it is clear that leafblowers are way overused these days. When the pandemic lockdowns began last year, many people suddenly found themselves besieged by the constant blaring hum of leaf blowers. There was literally no place to go to escape the noise because the low hum actually goes through walls. People were ordered to stay home and limit travel, so stepping out into the backyard or taking a short walk around the neighborhood was the only option for getting some fresh air but too often that air would become filled with loud noise and clouds of toxic dust. People were/are spending more time at home and it is no surprise that over 100 cities and towns across the USA have implemented bans and restrictions on gas leaf blowers. I, too, recently asked my small town to do something about these disruptive machines after spending most of last year with nerves on edge (I wrote an article about that) but this is not a new issue. Several large organization, like the American Pediatric Association and the American Lung Association have been alerting us for years about the detrimental effects of air pollution and there is no machine more polluting than a gas leaf blower with its 2-stroke engine and ability to blow toxic particulates into the air. Now there is also more information about the effect of constant noise, especially on the brains of growing children.

Another detrimental effect of leaf blowers is that they frighten birds and wildlife, and blow insects, caterpillars, cocoons, etc away. Imagine a huge, noisy vacuum suddenly appearing over your home but instead of sucking everything up, it’s blowing everything away creating a massive tornado that flings you into oblivion. That’s how wildlife must feel with our constant use of leaf blowers. Would you want to stick around and have this happen constantly? No, you would probably abandon your nest and go elsewhere. Hopefully, your nest would not be full of baby birds!

So what are potential solutions that have been implemented or suggested:

• Bans on gas leaf blowers in favor of electric leaf blowers which are less noisy and don’t produce emissions
• Leaf blower use restricted to certain months or seasons vs. all year round.
• Mufflers on leaf blowers to dull the noise.
• Using manual tools instead of a leaf blower.
• Getting rid of the sterile lawn aesthetic and leaving the leaves to mulch in place.

Environmental racism:

According to Robert Bullard, author of the book Dumping in Dixie, environmental racism is “any policy, practice or directive that differentially affects or disadvantages (where intended or unintended) individuals, groups or communities based on race.” There are examples of this all over the country. The flint water crisis in Flint, Michigan is one of the most notable examples in recent years but there are many landfills, dumping zones, slaughterhouses and other toxic sites or proposed sites in communities that are predominantly Black, Latino and low income. These sites cause pollution of air and water, and have detrimental effects on the people who live in those communities. This is such a big problem that a few months ago President Joe Biden signed an executive action “creating a White House council on environmental justice and a pledge that 40% of the benefits from federal investments in clean energy and clean water would go to communities that bear disproportionate pollution.”

Sometimes environmental racism is not as overt as a dumping site; sometimes it’s as simple as a town cutting down trees and not replacing them or a town not allocating space for green areas. This contributes to the Urban Island Heating Effect, which causes temperatures to be higher due to the sun’s heat being reflected off of concrete, buildings, roads, and other hard surfaces. So many people think that certain areas are run down or full of ugly buildings due to a lack of community participation or care; they don’t realize that so much of that is by design. Certain areas have been stuck with the crummy things that nobody wants in their backyard and some have been neglected altogether due to a lack of concern by the towns and cities that manage them, not the residents of that particular area. Think about that when you visit a neighborhood and feel the need to judge the residents of that neighborhood.

There are many other topics within the gardening world that keep people debating in online forums but these are the most common at the moment. If I missed something or you’d like me to write about another gardening topic, let me know in the comment section.

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