Is boxelder maple (Acer negundo) native to the Greater Toronto Area?

I’ve seen many sources that say that A. negundo is invasive in Ontario. It seems that this is right, for the most part. However, I’ve seen some sources, such as this map from Wikipedia, that seem to say that A. negundo is native to a few small pockets of the province. However, that map is all I can find on the topic. I don’t want to pull A. negundo if it is native to here, but I don’t want to leave it if it’s invasive, as most sources I’ve seen say. Does anyone have more info on the species’ native range?

One thing I can tell you is in Vermont it is native in part of the state and considered adventive if not invasive in other parts of the state. And we aren’t a big state either. Seems like this is one of a few grey area ruderal species. Maybe best kept “unknown” status.

I don’t have an answer for you, but there is a relevant feature request that might be of interest:
https://forum.inaturalist.org/t/add-one-but-only-one-new-establishment-means-category-uncertain/3805

In what state? Do you mean Ontario? Because that would be a province, and a big one. Are you talking about your state?

And I don’t want to let it stick around if it’s going to be wiping out native species, which is why I’m personally not content with not knowing the status

That would be useful for iNat, but doesn’t help me figure out what’s native or invasive to my specific area.

oooops, I thought I specified Vermont but I did not so my post made no sense. I edited it, thanks.
In terms of habitat restoration or land management i’d take that one on a case by case basis. If it crowds out other species i’d cut or pull it. In our little field, i am letting some woody plants grow up but am pulling the box elder out mostly. I want to keep it mostly open still and don’t want that to be the plant that takes over.

So it’s not like swallowwort, buckthorn, or garlic mustard, where you should always pull it out if you can, but more of a “pull it out if it’s becoming a problem” situation?

We do also have our natives - silver, red, and sugar maple - that can probably fill the same niche as boxelder does in most cases, without risk of being invasive.

i mean, that’s my take here in Vermont, but it may be different there.

Fair enough. The point of mentioning the feature request is that in cases like yours it may not be possible to provide a definitive answer, and currently iNaturalist doesn’t have a very good way of handling/labeling that kind of situation.

Moreover, I would feel a bit queasy having information gleaned from an iNaturalist forum become the basis for a “pull / no-pull” decision for any area, except in really clear and unambiguous situations.

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Keep in mind that it’s a distubance-dependant species, and the habitats it mostly occurs in by nature are floodplains and riparian habitats. By early accounts, even in its extensive primary native range it was not an abundant tree prior to settlement. It’s been very successful at reproducing in the wake of human land use changes, as a large-scale disturbance. In that sense I wouldn’t consider it “invasive” in the same sense as other species that disrupt habitat themselves; box elder simply does well in habitat that’s been disrupted.

That said, if boxelder seedlings are disrupting your efforts to get certain herbaceous plants established in a restoration sites, no reason not to pull them. If they’re not crowding out your desired species and you’re aiming to reestablish a forest canopy they’re probably nothing to worry about. As the canopy becomes successionally mature their reproduction will drop off anyway, and their roots will help develop the soil in the meantime.

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In John Macoun’s Catalogue of Canadian Plants, published in 1883, he says (under “Negundo aceroides”), “A few trees of this species are found near Toronto, in the valley of the Humber, about two miles from its mouth.”

The catalogue is basically a list of known locations for each species, based on Macoun’s explorations and reports sent to him by letter. A relatively small number of people with botanical knowledge surveying a large, relatively new, under-explored, and mostly-still-inaccessible country probably missed some things. (A lot of things, actually…)

Anyway, based on that, I would say yes, it is native to Toronto. Range maps for the species in older publications generally include southwestern Ontario in the native range, in whole or as scattered pockets.

There are a few sometimes-adventive, native-to-North-America species where it isn’t clear what the limit of the historic distribution is - and realistically, this can’t be known without a time machine. Black Walnut would be another example - large old trees in natural stands in southeastern Ontario never made it on the distribution maps of the 1950s; discoveries since then are often dismissed as “outside the known range” without proper consideration.

Since distributions are somewhat dynamic over time, if the species is in a natural setting and not causing any particular problems, I’d say leave it. I definitely wouldn’t consider A. negundo invasive in truly natural settings; although it may appear that way in heavily disturbed, early-sucessional situations, it would eventually be replaced by other, larger trees (like a (Sugar/Red) Maple-Basswood-Elm-Beech community). In an urban setting with limited space, it can be weedy, and it grows fast - so maybe it isn’t desirable there.

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For context, that’s around the same time Vincetoxicum showed up in Ontario, so being present in small numbers in the 1880s isn’t in and of itself a strong case for a plant being native.

Acer negundo is native to Manitoba, and it was my (possibly faulty) understanding that it was also native in adjacent NW Ontario, but had expanded its range south and east with disturbances caused by European settlement. I’ll try to dig up some references to support that when I get to work.

Regardless where it came from originally, it’s definitely weedy in southern Ontario now, and I wouldn’t hesitate to pull it out in any context where there were more desirable plants (i.e., habitat restorations or my tomatoes) I’d rather be growing!

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Thanks for the input, y’all. I think I’ll leave it alone for the most part, because I don’t have any habitat restoration projects that I’m currently doing. It seems that it’s not a garlic-mustard/buckthorn/swallowwort type plant that choke everything else out, which I would consider “remove at any chance you get” plants

Presence alone, no, but context is important here too. Distinguishing native and adventive populations is often based on whether a species is in a “natural” setting versus opportunistically capitalizing on an anthropogenic one. This describes established presence in the natural habitat the species prefers - not in a disturbed area. Supporting the possibility of a natural, post-glacial distribution, southern Ontario’s flora has a strong midwestern affinity, with much dispersal happening during the hypsithermal period and concurrent expansion of tallgrass prairie into the region. It “fits”.

Regardless, it is weedy now, as you say, and it no doubt has expanded its presence. There is no particular need to retain it, if it is in the way - but there is no need to eliminate it, either, if is isn’t.

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I just wanted to share my views on A. negundo - i’m the resident of the whole another continent where this maple was brought from Canada as the sources point out around XVII. It was planted in Saint-Petersburg Botanical Garden in 1796 and quickly spread out through Russian Empire first and then in 1920-s throughout Soviet Union.

Here in post-USSR countries it’s simply called american maple or ash-leaved maple, it’s highly invasive and really hard to get rid of - even if you burn down the stump, fresh sprouts start to emerge next spring - that’s firsthand experience.

I grew up in East Kazakhstan nearby Irtysh river bank - stunning old-growth mixed willow/poplar forest with abundance of wild apples and bird-cherries - and it hurts my soul to see how this very maple is taking river bank step by step pushing out native species and limiting their growth. I’m not sure if it emits certain chemical compounds, but nothing grows under it except some grass, whereas under willow and poplar canopy you can always find various fruit-bearing shrubs and berries - Viburnum sp., Rubus sp., Sambucus sp., Crataegus sp. - you name it.

Whenever I’m in the forest and I see one of A.negundo growing - I chop it down. But we need much more than one person could do. That’s my sad story. Sorry for the off-topic.

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This link suggests that the Manitoba Maple is naive to southern Ontario, They are are decent trees, but their lifespan is not long.
https://www.ontario.ca/page/manitoba-maple

I don’t know how it got into the USSR/Russia, but it will find an equilibrium. NA has it’s own imported fauna and flora that has changed our ecosystem.

Well, humans tend to sсrew up things everywhere.

As I’ve mentioned earlier it was imported as an ornamental plant, and I gotta admit there are some really good looking phenotypes, especially varegiated forms. Thanks to Soviet dendrologist it was recomended for urban landscaping which allowed it to spread quickly.

The thing is it has much quicker reproducing cycle than local dendroflora and it got no natural pests - maybe some Trametes sp. infect it occasionally.
It is already in Black Book of Russia and it’s recomended to take it down with chemicals. Hopefully, Central Asian countries will adopt similar measures soon. We ain’t got much forests here.

I was wrong - I found this, Silvics of North America. It indicates A. negundo’s native range just made it across the SE Manitoba border into NW Ontario, and also crossed the Detroit river into SW Ontario. It’s not a big stretch to get to the Humber River from there, particularly since the actual distribution of Acer negundo is obscured by more recent spread across the continent.

Unfortunately “reaching equilibrium” can come at the expense of extinction, ecosystem collapse, and a bunch of other human interest and environmental ills. So it’s not really a meaningful or comforting statement. The damage will continue long after we are dead, my kid’s grandkids are dead, etc.

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