yeah this is (in my opinion) a completely unscientific website that posts a lot of misinformation, because they didn’t want a specific eucalyptus grove removed. Years ago i responded to one of their posts asking why don’t they document the biodiversity on inauralist in both a eucalyptus grove and a native plant area, and a restoration site, to document any findings. They declined.
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I’m a huge fan of the old giants myself. There’s a certain spiritual quality to them that is hard to put into words, but when you’re standing underneath one you just get it. With proper stewardship and a lot more public awareness we’re on track to having more old growth forests here in North America. I haven’t seen the Cathedral Pines yet but plan on visiting once it gets cooler out. I’ve been meaning to buy Tom Wessels’ books at some point too, as it was his videos on YouTube through the New England Forests channel that really had a profound impact on me personally. Anyway, thanks for the link; I hadn’t seen that before.
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Ah… it seems like the people I described here are part of the same small but vocal group as the “gardenrant” author who spurred the original post. It’s disappointing that they’re so vocal with their antiscientific misinformation. But making that connection is also strangely comforting, because it indicates that this viewpoint may have a lot less traction than I feared. Thanks @charlie for connecting the dots.
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yeah this idea has been around forever, to be honest a lot of it seems like contrarianism. Propose anything, and someone will vehemently be opposed to it.
These people often complain about ‘native plant purists’ but i find actual native plant purists are very very rare. I’m more obsessed with native plants than anyone i know and i keep my non-invasive horticultural selections in my landscapes most of the time unless there’s a reason to get rid of them (maybe ‘someday’ they will be all replaced with native plants but realistically, no they won’t). Maybe some people get too zealous about ‘hating’ invasive plants (a waste of mental energy, they are just plants) and certainly there are some inavsive species control efforts that are a complete waste of effort, like little postage stamps of removing Japanese knotweed or giant reed when there’s a bunch upstrean that will wash back into the site. Use of herbicide is a complicated and challenging issue for sure, i think of it as a bit like chemotherapy - really not ideal, but sometimes the only way to save a landscape, and other times not worth the side effects when what you are trying to save can’t be anyway. But the million trees contingent is a loud and probably very small internet group that is nevertheless very visible. I haven’t been to the eucalyptus grove in San Francisco that sparked that particular website, so can’t comment too much, but the ones i’ve seen to the south felt very ecologically dead and huge fire hazards so… yeah. I understand why people want to retain trees on the landscape, but i find it questionable to say the least.
The idea of linking planting native plants to disliking immigrants comes up in that group and is super problematic on a bunch of levels and doesn’t hold up at all…
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Just came across this study: Genetic characterization of hybridization between native and invasive bittersweet vines (Celastrus spp.)
As someone who is often guilty of looking at things with an animal-centric view, I thought this study provided a unique perspective. Very often, native plant critics use the argument, “but I see pollinators on it all the time.” Ignoring other potentially problematic components of that statement (e.g., only generalist pollinators?, providing the correct nutritional balance?), non-natives can still have negative impacts, even if those impacts are not animal-related.
American bittersweet (Celastrus scandens) is an uncommon and declining native plant in North America. This study found that the unidirectional pollen flow from oriental bittersweet (Celastrus orbiculatus; a prevalent non-native in North America) prevents the native bittersweet from reproducing. So, oriental bittersweet’s ability to attract pollinators is actually one of the things that makes it detrimental.
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The only native plant purists I’ve ever encountered have been online. Obviously it’s a much bigger sample size but I’ve been adding native plants to my landscape for about 6 years now and even at exclusively native plant nurseries, I don’t run into “purists”. Most other folks who champion the benefits of native plants like myself also like and keep some non-native/non-invasives in their gardens.
I’ve seen the “intolerance for immigrants” argument a number of times and it just doesn’t hold water for me. Are there some people who are “nativists” who don’t like immigrants? Well, maybe, but I don’t think the two are linked or linked as closely as some make it out to be. I take the opposite view-- proponents of native plants and habitat restoration see the value in what is indigenous to a particular place instead of going along and continuing to erase what was here before.
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Hybridization is another overlooked and insidious consequence of some invasives getting a foothold in new places. Siberian elms which were planted heavily in North America after Dutch elm disease swept through, will readily hybridize with the native red (slippery) elm. White mulberry which was brought over to help jumpstart the failed silkworm industry has now overtaken the native red mulberry in North America through birds spreading the seeds far and wide, as well as some hybridization.
I’m not exactly a native plants purist myself, but it’s the least I can do to simply not add to the problem. Things like Oriental Bittersweet might feed the birds, but at the cost of girdling the trees. Japanese barberry and multiflora rose also feed the birds, but at the cost of hindering natural forest regeneration and displacing native ground cover. There is a field in my town that was abandoned 25 years ago. Today it’s full of autumn olive and callery pears, in spite of the surrounding woodlands being full of sugar maples and red/white/chestnut oaks. The more there are of any invasive species, the more there will be…
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I think part of what some people are responding to is that the removal of invasives doesn’t always get accompanied by planting natives. For example, sometimes folks in my area just cut down large quantities of exotic shrubs and leave them to decompose or burn them, without making an effort to replace the carbon storage capacity the shrubs had.
Those methods may not involve herbicides, but they do involve permanently destroying all the vegetation in an area (in order to replace with new plants), which I think we can agree is a pretty dramatic change, ecologically speaking. I think it’s important to be fully aware of what is being destroyed when bringing a parcel to a state that land managers prefer. And I disagree that it’s ridiculous to put forward concerns about that initial destruction. Some of these sites have already undergone dramatic human-caused disturbance in the past, which is what led to their transforming into a lower-diversity plant community in the first place. Destroying everything again in order to replant natives could be seen as restoration and it also could be seen as (in some ways) continuing a pattern of human destructiveness. What if the weedy old field is part of a longer-term natural response to the prior disturbance, and we are interrupting the land healing itself when we try to wipe the slate clean?
In general this study looks solid to me and it seems logical to me that natives would support greater abundance and diversity of caterpillars. However, it is worth noting that the authors of this study excluded non-native caterpillars from the analysis, including Lymantria dispar dispar which apparently is eaten by a number of different birds. I’m not sure to what degree inclusion of that species would or wouldn’t have changed the results.
That might be true but do we have evidence of that?
While I don’t think we should ignore any harms brought about by invasives, I don’t see a problem with bringing forward an attitude of love at the same time. We can have love or at least show a certain baseline respect for all living things without needing to support everything we perceive them doing. In contrast, I’m disappointed and concerned about how I learned to hate invasives when I was training in conservation, in part, I think, due to the language I was surrounded by. Some of the language used in invasion biology sounds to me a lot like a combination of hatred and fear, and I’m concerned that when we act from that place we may not see the full scope of the truth or the options before us.
While I don’t support the use of epithets like “nativist” – which seem to mainly divide us rather than help us understand each other – I do see significant parallels between the language sometimes used against exotic plants and the language used against foreigners, immigrants, and refugees in the human world. There can be a common sense of opposition or wariness toward the outsider and a desire to protect or uphold the insider. Examples include referring to exotics as threatening or menacing. This article uses those terms and additionally refers to exotic gene flow as genetic pollution:
https://doi.org/10.2307/2446487
What does that purported parallel say about the so-called “nativist” perspective? I won’t claim to know, but I do think it’s something that’s worth reflecting on and getting curious about.
Why would the size of the group or their vociferousness be relevant to whether they might be on to something? As for the charge that they are being unscientific, there may be some truth to that with these particular authors, but at the same time, it’s also true that there’s recently been a decent scientific debate within the field of invasion biology about some of the basic tenets of the field. I looked into the literature recently and was surprised by the vigor of the discussion going on.
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I can’t speak to your area, but in my area, we make space for fynbos to return. Either from the seedbank, or returning from neighbouring fynbos. A certain amount of deliberate growing locally sourced plants to restore the population - but that is a much smaller volume. The intention isn’t to rush in and replace these shrubs with those shrubs.
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It really depends on where you are working. In some areas planting can help a lot, in some situations it doesn’t help or even can be harmful. For instance, sometimes there isn’t locally sourced native plants and what you can get isn’t appropriate for the site, and sometimes lots of native plants seed in on their own.
In my area invasive shrubs aren’t really a good carbon sink, they form a dense layer on the forest floor but they inhibit growth of larger trees and i don’t think they build soil carbon very well. I don’t think laying them around in brush piles is always bad ecologically, though it can be an issue in fire hazard areas or aesthetically.
Well the whole point is that invasives inhibit this process. Sure there’s lots of grey area and it’s not always that simple, but if there’s some non-native plants there as part of natural succession, like dandelions in a field where native trees are starting to sprout, they aren’t really invasive, just non-native.
Yeah, i get that, that makes sense. I guess i am using ‘love’ in a different sense here, not in that we should not have love for the wonder of nature and the adaptability of organisms that end up invasive after being moved or habitats change. I mean ‘love’ in the sense that people advocate to protect and spread around invasive plants. I think it’s natural and even healthy to be angry at the state ecosystems are in. It’s true that we should be angry at human factors that spread invasive species, rather than be angry at a bush or something. But i’m pretty OK with hating multiflora rose, it’s pretty awful stuff. Sure i’m sure it has a place somewhere, but it’s horrible and will absolutely rip you to shreds.
I think this is a really bad path to go down. Humans are not plants, immigrants aren’t a different species. By this logic, NOT controlling the invasive speices caused by colonialism is also an extension of ongoing colonial genocide. Both of those statements may be a bit escalatory, but if one is true, the other one is true as well. Sure, an invasive species can be ‘threatening’ or ‘menacing’. So can a thunderstorm, but no one is saying my desire to not have a storm when i’m doing field work is somehow linked to a hatred of immigrants because the storm came here from another country. That’s absurd and honestly i feel that the whole ‘invasives = immigrants’ thing is no better.
People who are wrong, and overzealous are oftn very loud and monopolize conversations. Not always. And sure, someone who is correct may do this as well. But it’s sketchy how it’s been explained time and time again why invasive species are harmful and they persist with an ignorant view. Same as climate change deniers. They might have a valid point here and there - people do overreach what can be attributed to climate change - but the denialists are clearly ‘wronger’.
I think any scientific field is this way, look at taxonomy for instance. I think the taxonomic splitters are doing something harmful, but i don’t think they are doing it because they hate global unity and world peace, because taxonomy isn’t the same as how we operate nation-states.
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This (Buddleja) is a good example (that is why I made this -maybe a bit provocative- post)- some plants are promoted as very insect friendly, because we see many insects on them - but sometimes these insects are only generalists, or the plant is very good in attacting them even if it does not offer too much for the insects… - What I want to say: the nature conservation value for insetcs is often a bit more in the detail; Apart from this as already mentioned here, we often pay a lot of attention when it comes to providing pollen and nectar, but forget about the often very specialised larval stages
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Agreed that this is a bad place to go. Many invasive plants are actively harmful to established ecosystems, and absolutely need to be controlled for. Anthropomorphizing these plants and comparing language around them to language used toward Human Beings just doesn’t sit right with me.
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Perhaps I am missing it, but I don’t see where it says non-native caterpillars where excluded from the analysis. Lymantria dispar is not on the species list, but I see no reason to believe it was excluded. Lymantria dispar is not (yet) a commonly reported species in North Delaware where the study was conducted.
Atteva aurea is notably on the species list. While this species is native to the Americas, it is not native to Delaware where it feeds exclusively on the invasive Ailanthus altissima.
Also worth mentioning, while some birds may feed on Lymantria dispar and other non-native lepidopterans, this does not mean these moth species play a comprehensive role in the ecosystem. Native caterpillars support a whole food web of predatory stink bugs, parasitoid wasps, etc. Invasive caterpillars can reach such high abundance because they have a much reduced suite of predators in their non-native range.
I was very excited when I saw my first native European Starling when I visited Europe. I don’t hate the species. I think they are fantastic birds with an important role in their native ecosystems. It’s in their non-native range that they are problematic. Even so, I blame the people that carelessly introduced them, not the species.
I would like to counter this by saying I think the parallels are much stronger with colonialism. The idea that introduced species are somehow inherently better than the indigenous species they replace based purely on the merits of the invaders’ success certainly fits the bill.
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I love Douglas Tallamy’s books! My favorite is Nature’s Best Hope, which sparked his Homegrown National Park program that encourages people to plant natives in their yards. Check out their website!
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From experience I can tell you that while some insects can interchange their host with another similar one, there are far more cases of insects being very narrowly specific. In those cases, they can’t or aren’t willing to adapt to alternatives before their population ends up dwindling. While you can use successful insects as proof to support native plants aren’t needed, people are not paying attention to the insects that are now missing from that circle.
This is neglectful science, but I don’t blame horticulturalists for believing it. One of the banner organisms is the monarch for instance, that’ll happily switch to other milkweed species. Most garden “pests” also freely motion towards related plants. That’s the reality most folks notice and so they think it’s the full story.
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Speaking of Monarchs brings up another good point. In the few instances where native insects will readily use non-native hosts, there may still be less apparent consequences.
Monarchs have coevolved with Tropical Milkweed (Asclepias curassavica) where their ranges overlap, but Tropical Milkweed can cause problems for Monarchs when it’s planted and introduced outside its native range.
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This!
Getting back to the insects, it’s true that things are complex, some non-native plants can support important native species, and some native plants do little to support insects, but OVERALL, the plants native to an immediate area will support the insects native to the immediate area, because they evolved together, and thus are basically ‘made for each other’. So while you can find non-native plants that also help, and while non-invasive non-native flowers are almost always better for native (or introduced) insects than lawn or concrete, overall as a rule ‘plant species native to your immediate area’ will provide better results and a lot easier than trying to parse out every single insect and plant species and who uses what.
It also really depends on where you are. I live in Vermont where there is still a lot of native habitat around so native insects like fireflies and bees can easily find native plants i plant. Other areas, like the UK, sound to be so disturbed that there aren’t a lot of non-generalists in most areas anyway so it might not make as much difference; conversely places like California and South Africa seem to have such narrow endemicism that just planting species native to the broad area might not even be enough.
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It is sort of surprising to me that some gardeners believe native plants are unattractive. Even some of the pro-native plant people act like planting native plants is like eating their vegetables! At least where I live, and where my sister’s lived in the midwest and the east coast of the US, they’re incredibly beautiful! Nothing like shooting stars, camas, and irises in the springtime. I started trying to garden with 75% native plants, 25% nonnative in the last few years, and I’ve been very pleased with the results. There’s no going back for me!
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If you go to the very bottom of Table A1 in this paper there is a footnote that indicates a few caterpillar species in the table, marked by a double cross symbol, were excluded due to being non-native:
L. dispar was indeed found in the study but excluded from analysis – the species is listed in the upper third of the second page of Table A1:
Also in the table but excluded for the same reason were Ancylis comptana (Tortricidae) and Caloptilia azaleela (Gracillariidae). I take note of what you mention about Atteva aurea being on the species list and am not sure why it would not be excluded from analysis if those others were.
The enemy release hypothesis definitely has some good support but just as a nudge in another direction, here is an example of a countervailing finding:
https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/14-2158.1
I agree that seeing invasives’ success and then declaring them superior to natives on that basis would be problematic. To be clear, I am not arguing for that position (perhaps the writers cited by the OP were). I do think that in ecosystems already heavily damaged by past colonialist human activity, exotic species may have a short-term adaptability advantage compared to most natives who have never experienced that kind of disturbance. This doesn’t make them morally superior, just better adapted to conditions they’ve seen before but natives haven’t. We certainly don’t have to like that fact, but nor do we have to hate it.
As for the question of parallels to human migration, I think there’s room for acknowledging similarities with both immigration and colonialism. In both cases the new arrival changes things and the old guard confronts the reality of the change. People seem to need to talk about these things by including a bad guy and a victim in the story, and while malevolence is sometimes clearly present (smallpox blankets, treaty violations, etc.), it seems to me the truth is at other times more murky. Can we ascribe intent to a plant? If buckthorn has malicious intent (as the allelopathy story about it goes), and we feel justified in eradicating it because of that, does that mean that someone should’ve killed off the supremacist colonists in North America before they spread too much? The analogy with immigration may break down at some point, but I would say the one with colonialism does too. That doesn’t mean the parallels aren’t relevant (I am quite convinced they are very important actually), just that there’s a limit to what we can understand with them.
On the related note of what gets called anthropomorphizing, I would ask, what specifically are the interior qualities we are scientifically sure humans have that plants do not? I don’t think anyone can prove a plant has a soul, but neither can anyone prove a plant doesn’t have one, and we don’t let a little thing like proof keep us from ascribing soulfulness to ourselves. I don’t want to wander too far off topic here but I do think it’s a relevant line of inquiry.
I hear you re: overzealous/monopolize, I’ve been there in convo with others.
Who are you saying is persisting with an ignorant view? Are you referring to the gardenrant author?
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I hope my points are heard with an open mind, as I have no desire to get into a personally charged back and forth. It is my thinking that most problems today, including social, can be helped along if we start with where we might find common ground, so please read this with that in mind.
As someone who contributed to this Garden Rant, I ask you to try to find those connections as you read.
First of all, none of us quoted in the Rant are supported by Big Hort or turfgrass associations. We are people who care immensely about the natural world and for doing best by our planet and its need for biodiversity.
I learned of the work done by Conservation Sense and Nonsense, while searching for research that supported my own experiences as a lifelong gardener and naturalist. I have witnessed many many examples of native wildlife, insects, lepidoptera and yes, even specialist insects using plants that are not considered native. (I am 72, and have spent many hours interacting with nature in landscapes, gardens, cropland, and in the wild, and have personally witnessed the interactions with both nonnative plants and native. (Debating that term is another issue that deserves attention when you consider planetary time - dinosaurs, ice ages, etc… and the fact that all continents were once one, with the north American east coast once lying below the equator: and that many species of flora and fauna were exchanged over the land mass that connected Alaska with Siberia, and so on). I marvel that we dare try to proclaim the one correct plant palette to be the once when Europeans arrived? How do we know a “native species” did not arrive a few decades or centuries before “we” did, blown in by storms or carried by birds?
I digress. What we have seen is that wildlife does often avail itself of nonnative plants, yes even some specialists. The founder of Conservation Sense and Nonsense actually did witness a horrifying loss of habitat in the name of native plant restoration. Each day on her walks with her dogs, she passed through a rich area for wildlife and biodiversity that was destroyed and replanted with natives that struggle on that challenging site.
While her heart was aligned with the intentions, she witnessed the real consequences and began to question the methodology. At much cost of personal time and no, I repeat, NO commercial or financial reward, she began to ask questions, and we discovered each other in our efforts. More connections emerged over time. In spite of the negative pushback and character attacks, we continue our mission in hopes it will help neutralize the efforts to remove useful habitat, and ask for consideration of the contributions of some nonnatives on a species by species basis, rather than condemnation using the broad brush of origins.
The “small but loud” voices are not “pro-nonnative”. They are pro-beneficial plants. They are pro plants that can prosper in today’s highly disturbed and overdeveloped circumstances. They (we) are simply asking if a plant can be judged on how well it benefits local ecosystems before deciding if it should be destroyed. Can it survive with fewer inputs, on hotter and drier sites? As these nonnatives often thrive on terribly scarred and challenging sites, can they be considered as part of the process of recolonizing that site as plant detritus helps build soil quality and slows erosion? Is it possible to evaluate them on a number of levels, for example, its ability to anchor soil, cleanse the air and cool hot sites? Should we be plant shamed when we advocate for using the most beneficial plant requiring the least input with the least detrimental impacts? Of course there are some horrific examples of nonnatives wreaking havoc but the even often maligned may need to be reevaluated in today’s (threatening) context of development, pollution and a rapidly heating climate.
We see mimosa on many a roadside and read of its evils. Mimosa is noted for its ability to flourish on extremely challenging sites with no human aid, thus its visibility making it a popular target. Yet mimosa is noted for its ability to remediate soils, removing terrible pollutants, in particular heavy metals from soils spoilt by strip mines or landfills. It is currently being studied for its usefulness along highways (where it thrives on its own) for its potential to reduce the detrimental effects of vehicle exhaust. In this situation I have often thought that advocating for its removal is telling Mother Nature she should not be trying to heal herself with the tools she chooses. Do we really know best?
Does mimosa spread rapidly? Yes, it readily reseeds even in continually challenging circumstances. But studied over time, it is a short lived tree with a low spread crown of filtered , not heavy shade, that cannot tolerate being shaded out, and so does not persist where the natural progression of wild fields (left to their own devices) will eventually become hardwood forest in my part of the continent. In other areas where that is not the natural progression, it can be the heat and drought tolerant species that provides shade and respite from rising temperatures, cooling the earth, making its own nitrogen, and providing sustenance for many species of wildlife, yes even for caterpillars such as the larvae of summer azure and Reakirt’s blue butterflies, likely more.
https://www.researchgate.net/publication/259459656_Selection_of_forest_species_for_use_in_urban_environment_in_relation_to_their_ability_to_retain_heavy_metals
http://www.dallasbutterflies.com/Butterfly%20Gardening/Host%20Plants%20by%20Butterfly%20Species.htm
If you can’t stomach the idea of mimosa, let’s consider this question. In today’s state or circumstances, would we be better off if we eliminated white and red clover? Both are heavily used by native bees a myriad of other pollinators, and yes, as lepidopteran hosts.
Should we discourage those gardeners who grow nonnative fennel and parsley for the black swallowtail caterpillars? Would it be beneficial to eliminate the aggressive European henbit that spreads an early spring feast for early pollinators in our agricultural fields in this region, before summer crops are planted? Would the wild turkey I see eating on the foliage of this henbit (thus the common name) be better off without it? No one plants it. No one waters it, no one adds commercial inputs of any sorts and its season of provision is ideal for those fields destined to be heavily peppered with inputs for producing human foods. May we plead its case and ask for similar evaluations of other nonnatives without being accused of having other motives?
We who are loud are simply asking to evaluate each plant on its own merits rather than country of origin, yes, just as we should do the same for each immigrant group of humans that do not deserve to be painted with a broad brush of negativity.
Might I also ask that our voices are raised because of the laws passed and those being considered that could prevent using the best plant for the job. We raise our voices because we know that limiting plant diversity can have devastating consequences. We know that a particular species can be the next victim of a pest or disease that ravages the population just as it has with American chestnut, American elm, ash trees, and now red maple being especially targeted by flat headed borers. The lesson we were supposed to learn was to not rely heavily on a single species in a suburban species. If easily grown nonnative trees can help with this mission, AND provide cooling, soil and water cleansing, carbon fixing, and wildlife habitat INCLUDING lepidopteran herbivory should they be excluded?? … and should those who ask these questions be accused of being subsidized by Big Hort or turfgrass associations? (BTW, the most common nonnative turfgrass choices in the southeast are excellent host plants for a variety of caterpillars. The important thing is to avoid pesticides and be timely and judicious when you mow).
I am very aware of the large number of books and publications that set out to prove the superiority of native plants. Yes, I have read Tallamy’s books. I have also done much deep dive into his research and would like to point out a couple of things to consider. Were the experiments set up to prove the superiority done without prejudice? For example, in the famous chickadee study, were all the parameters accounted for, such as were the lawns of the nonnative landscapes managed by turfgrass management companies that regularly pepper the lawn with pesticides? Were the nonnative plant landscapes selected largely populated with the least useful nonnative plants and the native landscapes with the most useful, because it that scenario were revered, it would prove the opposite. I am an academic, and know full well how authors send their manuscripts for peer review to likeminded colleagues.
The second point is that Tallamy’s own research discovered that about 85% percent native plants are not used for caterpillar herbivory. He also conceded that closely related nonnatives are utilized, even by specialists insects, and in at least one case (elms) the nonnative species was the preferred. I imagine if more genera were investigated, that might not be the only case of exotic preference. Certainly we should provide plenty of plants for lepidopteran larvae, but sometimes a plant can provide other extremely important services, such as in the fight against pollution of our air, soil and water. Should we eliminate the use of those 85% native plants that do not provide for caterpillars or give weight to the facts, that sometimes a plant can provide other extremely important services, such as providing nectar and pollen, fruits and nuts, helping in the fight against pollution of our air, soil and water, providing cover for wildlife and soil, and just making oxygen! All plants provide some service, native or not. Not all plants need provide all things. Nature says so.
Most importantly, I ask you if there is a way to debate the specifics without demeaning the motivations of those who are genuine in their efforts to provide the best habitat in each circumstance, in today’s dire time of need. Please use natives where this is the best choice. Please use nonnatives where this is the best choice. Please let the criteria be “most good” for the site and services performed.
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