Undesirable plants as beneficials?

Nature Talk
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I’ve been shooting pollinators here in the San Antonio area for the last few weeks in urban parks. I’m not seeing a lot of natives blooming right now. What I’m noticing is that Poverty Weed and Vitex (which are blooming) are absolutely mobbed. Same with planted specimen Lanatas. I’ve seen so many interesting pollinator species. Many consider Poverty Weed as a noxious native, and Vitex and specimen Lantanas as invasive.

Anyway, it led me to wonder if plants like these might actually be a benefit in urban areas where habitat loss/derangement is so high. Maybe some of these tough “undesirable” plants are helping to save vulnerables and pollinators in general?

For example, I’ve noted several Sonoran Bumble Bees on these plants, but I’ve found them nowhere else. One blooming Vitex had at least 30-40 individual American Bumbles swarming it. Both Bumbles are listed as vulnerable. And today, I noted 5 species of migrating and winter resident birds on Poverty Weed, snacking on both nectar and insects.

Is anyone aware of a project here looking at undesirable plants through this lens? I’m not taking a conservation position here, just wondering if there might be a bright side to consider.

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747 invasive plant projects.
Might be something there?
You could start a project - a traditional project where you choose which obs to add?

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Invasive plants covered in pollinators is usually a sign that native plants are missing in the immediate vicinity or you’re in a seasonal gap (especially with climate change extending spring and fall faster than phenology is changing).

Noxious as applied to native plants usually refers to farms and rangelands and should be ignored for pollinator conservation.

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Undesirable plants as beneficials?
Happens all the time.

Invasive Tree Rescues Arizona Town! (Andrew Millison)
https://youtu.be/Oayt7eru2nc?si=c-cdrVnDB_BnjOq2

It’s shades of gray . . .

(Sorry I didn’t actually suggest a project! Feel free to delete if considered off-topic.)

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@ DianaStuder There are definitely a bunch of invasive projects. At a glance, they start from the premise that invasives are bad and should be eradicated. Which I get. Ideally it would be great if a scientist structured a “beneficial invasives” project so some kind of useful data could come from it.

@ egordon88 Agreed that natives are missing. Some natives have such niche requirements that they simply can’t make it in a disrupted/disjointed urban environment. Ripping out the invasives and seeding natives might help in some cases, but not all. Good point about climate change putting pollinators in a tough spot…they need plants at a certain time, but the timing might align less and less in the future.

@ AdamWargon Thanks for the links. No worries on not suggesting a project. Tree of Heaven, wow. I wonder how that will work out? I guess the town’s Chi will be in good shape :grinning:

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you can do that yourself. Otherwise you wait, till someone else decides they are interested. Meanwhile you could be collecting data.

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I think there are still a lot of unknowns around whether or not invasives / non-natives can be beneficial to pollinators. The real answer is probably “It’s complicated”. But here are some things to consider.

The fact that I might see as many bees on spotted knapweed (invasive) as monarda (native) doesn’t make them equal. Pollinators evolved with native plants, so we know those plants have everything they need. Even if non-natives provide nectar, it might not have the same nutritional value. It has been suggested that some invasives could be the equivalent of junk food. In the U.S., you could make the argument that french fries must be beneficial to humans because they seem to prefer them to vegetables.

Pollinators need more than food. A lot of invertebrates require specific host plants for their larvae. Monarch butterfly larvae need milkweed. Regal Fritillary larvae need prairie violets. Endangered Karner Blue butterfly larvae can only eat Lupinus perennis. Natives plants provide everything they need.

I don’t doubt that non-natives do provide some benefit to pollinators. But if they are planted in place of natives, or if they become invasive and crowd out more natives, that’s ultimately not a benefit.

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Presence on something does not necessarily equate to beneficial. I see a lot of people eating McDonalds, but that doesn’t mean it’s healthy.

What usually happens from what I’ve seen is non-natives will benefit one thing, but are detrimental to a lot of other things. Or benefit a small amount of species of concern, and a whole bunch of other non-natives.

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Here are observation of that bee in San Antonio so that one might consider what plants it associates with:
https://www.inaturalist.org/observations?place_id=49994&subview=table&taxon_id=57690

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Might something like Pollinator Associations be helpful? This particular project collects observations of the pollinators rather than the plants, but there is an observation field for the host plant, and I suppose there must be a way to work with that data in order to find pollinators visiting invasive host plants.

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Lots of invasive plants attract high numbers of pollinating insects, which is why they’re so prolific and infestant. Anthropized environments have no shortage of nectar-rich flowers for insects to feast on, but they lack habitat and vegetation that can sustain wildlife in all of its life stages, contributing to a rich and complex ecosystem.
Non-native plants tend to sustain very little biodiversity, while their aggressive growth pushes out species that do.

beneficial invasives

That’s an oxymoron, an invasive plant is a non-native species whose presence has been proven to be detrimental to the environments it colonizes.

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On iNaturalist and elsewhere, one finds plenty of people who will say this about every non-native species.

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Thanks for the thoughtful replies.

I don’t suggest we plant any invasives. I was thinking the other way around. Imagine that myself and other well-meaning naturalists went out this summer to rip out that Vitex. It’s the only Vitex I’ve seen on that three-mile stretch of urban greenway. I wonder if that action would have had a positive impact on the frantic bumbles I saw feeding on it this October? I’ve looked long and hard around my city, and this Oct is the first time I’ve seen the Sonoran Bumble in anything other than a nature preserve. I saw at least 4 on that lone Vitex shrub.

Back in the late 80s or so, I knew a doctor who did volunteer work in Africa. I was horrified when he told me that they regularly infused HIV-infected blood into patients. (This was way before there were any treatments for AIDS.) Seeing my expression, he said, “Should we let them die on the table for lack of clean blood?” (Yes, I was a young first-world idiot, and humbled.)

If your choice is junk food or not enough food (=death), then surely junk food wins. It’s obviously not what any of us would say is a good situation. But could it make sense to lower the bar on our idealism in asking urban areas to live up the standard of the habitats that they’ve long since destroyed? Is the perfect the enemy of the good here?

I know there are no simple answers. I’m just saying that it can’t hurt to keep an open mind, given the crazy rate of change on our planet.

@taylorse Yes, that project sounds perfect. I often note the species of plant the pollinator is visiting. Thank you!

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Sorry to blather on, but thinking about this Vitex shrub and talking to others this week has crystallized something that’s been nagging at me for months about what we call conservation.

Some posters here commented that this one Vitex shrub is being mobbed by bees because there aren’t enough natives blooming. No argument there. Very little is blooming here right now. The assumptions I heard from some was that invasives have overtaken native niches, thus no flowers. I don’t see a ton of invasives on my walks, but they could be part of the issue.

Regardless, I believe the main reason that few natives are blooming this fall is simply for lack of rain. San Antonio is one of only a few major metro areas that have seen the US’s dry/wet line pass right overhead and off to the east.

This line used to be the 100th meridian, but now is more like the 98th, just east of us–and this shift has happened since only the 1980s. We are now nearly always in a drought…anywhere from moderate to severe. At some point, we have to call this arid side of the line our new climate normal.

Surely many native plant species that are used to higher rainfall amounts of millenia past are going to suffer. Any plant on my local greenway that needed decent summer rains to bloom this October didn’t get it. The Vitex tree in question was growing in a low spot that is a natural collection area for the scant rain we did get. Thus its October bloom, and thus the bees flocked.

Again, I’m not making a pitch for non-native plants per se, but what I have come to think is this: I’d like to see a change in our environmental goals.

“Conservation” is by definition backward-looking. The expectation of many is that our greenways today should look like they did in 1857, or whatever year you like. Clearly that isn’t possible. We can’t remove all the plants in our greenways/flood plains and reseed. We could in theory lay a short-grass prairie seed mix and hope that the seedlings could compete against the current flora AND that they would get enough rain to do so.

But if drought (and heat) is our new normal, that short-grass prairie seed mix of 1857 might be a big waste of money…any plant in the mix that isn’t drought-adapted will not survive.

I think it makes more sense to be forward-looking. Maybe “responsive stewardship” would be a better term than “conservation” for areas that are in rapid flux, such as those of us now caught in this drastic dry/wet line shift.

The head of our nascent arboretum is asking Texas universities the same question: would it even make sense for the arboretum to replant our native cedar elm when they’re dying off (drought / severe winters being at least two culprits). I like this open-minded way of thinking.

So this was too many words to restate my point. Tough “Invasives” may have benefits if water-thirsty natives are no longer fit for the new arid climate regime we find ourselves in here. Maybe we should rethink ripping the invasives out with the goal of turning the clock back to some past habitat flora mix. I hope scientists are thinking more responsively about the future, instead of reflexively hoping to resurrect the past.

I know many of you won’t agree, and that’s OK. It felt good just to get clarity on my own thinking, and maybe it’s food for thought for some readers.

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You may be interested in Buddleja davidii (butterfly-bush) in the UK - here it is a mildly invasive woody shrub - mostly annoying for humans, not nature, though occasionally it’s a pest on chalk grassland.

It loves human disturbed areas like old crumbling walls, railway sidings, waste ground, pavements, and demolition sites. When Britain was being bombed in the Blitz it was called the “bombsite bush” because of how quickly it colonised the rubble, and where you have waste ground, Buddleja davidii is the ruderal species - sure, you’ll get willowherbs, weedy yellow composites, various grasses… but none of them are as conspicuous as butterfly-bush. They compete terribly as seedlings and generally can’t establish once the cracks are filled by grasses and smaller plants, but once they’re going, they’re very sturdy, easily able to resprout when cut down where they’ll eventually reach 3 or 4 metres tall.

They are terrible hostplants; there’s one leaf-miner fly that will use them and there’s the Mullein moth - both are more or less happy on native figwort-family plants. But you will still find generalist pollinators smothering it - be it because they don’t really have hostplants (bumblebees, various hoverflies), or their hostplants are very common (the ‘garden butterflies’ that like other waste-ground icons like nettle, or the mustard family). It’s abundance in cities almost certainly helps these generalists in places where other flowers are often scarce.

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My experience with Vitex.

Many years ago I kept honey bees. I read in a beekeeper magazine that Vitex flowered profusely during the heat of the summer when many other plants didn’t. This was beneficial to honey bees as a food source between spring and fall blooms. I bought some seeds. They have done well here in North Florida. The honey bees love them as do numerous native insects. Many photos I’ve posted on naturalist were feeding on Vitex flowers. In recent years I’ve noticed they have been spreading in my neighborhood. Now I’m starting to consider them an invasive. I cut a large one down the other day. I’m still considering if I should remove the rest of them. Just wanted to share my experience.

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I don’t know about Texas, but in Minnesota there’s been a lot of forward-looking discussion among natural resource professionals in recent years. Minnesota is fortunate to be included in four different biomes. But with the prospect of climate change, there is a real possibility that our boreal forests could someday be replaced by temperate forests, and our temperate forests could become prairie.

So for example, foresters now talk about planting trees in central MN that used to only grow in the SE corner of the state. And in southern MN, planting trees that previously didn’t grow further north than Iowa or Illinois.

Note that this is just a range shift that goes along with the shift in the USDA Hardiness Zones. Nobody is talking about planting non-native Eurasian species that may become invasive.

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That’s still settling for second-best. What if we could revert to the climate of 1857?

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Many prairie plants are indeed very drought-tolerant.

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