I try to provide information to help people learn and be prepared to make informed decisions. Over a number of recent posts, I have been discussing native plants, pollinators and healthy ecosystems. If any one part of the system is out of balance it can have a significant impact on the system as a whole.
To that end, I had a chance to talk recently with Dr Robert Gegear PhD, an assistant professor of Biology at UMass Dartmouth. He is a leading authority in New England and his research covers a broad range of topics but largely falls under the “factors influencing the dynamic interplay between pollinators and the flowering plants that they service.” His research focuses on Bees, as multiple species are easily identifiable, but I also heard him speak about research where he trained butterflies to be attracted to different colors, revealing that color choice is not necessarily hard-wired.
I also appreciate that Dr Gegear is direct and is and able to explain why it is critical that we work to restore our native plant habitats. It is important to hear strong opinions from scientists who are closest to the issues. I transcribed parts of our conversation as I didn’t want to be in the business of editorializing his comments. Spend some time on his website and look at his plant lists.
[Reed]: Do non-native plants in gardens hurt our native pollinators?
[Dr Gegear]: They should spend time eating the food that they should be eating or being on the plants that they should be on. Would you spend your life eating fast food or would you want to have a bit more nutrition in your diet?
Nutritionally, non-native plants tend to be inferior for bees. Bees need high-quality pollen to produce new bees, and non-native plants often have lower-quality pollen. For example, red clover is visited by many bumblebees of conservation concern, but its pollen is lower in quality compared to Penstemon (Beardtongue). As bees feed on non-natives for nectar, they also collect low-quality pollen, which affects their population.
The term pollinators has been abused so much that it’s meaningless and it no longer has the proper meaning and people tend to lose sight of the importance. So, when people say pollinator these days and pollinator garden, all they’re talking about is flower visiting insects and feeding animals.
But the issue is more about conserving their functional role as pollinators and that’s pollinators of native plants and preserving, restoring, protecting pollination systems, right? Which is the native plant and all the animals that visit. Not everything visiting a plant is actually pollinating it. In many cases, it’s 5% of what’s on there that is actually doing the pollinating. And that’s the important part.
[Reed]: One of the challenges faced in creating complete ecosystems is the limited space available in many gardens. With small lots it can be difficult to fit in all the necessary plants. It’s often impossible to include large trees like Hackberries, Willows, and Oaks, let alone the shrub and perennial layers.
The Homegrown National Park concept by Doug Tallamy encourages people to recognize that they live in a larger, combined ecosystem and don’t need to replicate everything in their garden. Do you agree with this?
[Dr Gegear]: Despite these challenges, it’s important to note that you don’t need a large space to make a difference. It’s possible to have a positive impact on conservation with just a quarter-acre of land by making the right plant choices.
For example, the common eastern bumblebee, Bombus impatiens, is all over the place and is an indicator of poor habitat. When we start to introduce plants that species of conservation concern prefer back into the habitat, even if it’s just a few plants, we start to see those bees on the plants. I have a quarter of an acre at home with these plants, and I’ve been able to bring Bombus vagans here, which wasn’t present otherwise.
I have plants for all seasons and various conditions, whether it’s full shade or otherwise. These plants help support those connections. We’re not looking at it as a single homeowner in their backyard, although that certainly makes some difference. Collectively, if five out of ten people on a block do it, that is enough to support the ecosystem.
[Reed]: Getting back to my original question, one that I often get is, does it hurt the system you’re trying to create by keeping, for example, the ‘fast food’ plants like catmint and lavender?
[Dr Gegear]: Yes, it does. Catmint and Lavender help honeybees and a few common species, but there are native plant alternatives that would increase pollinator diversity instantaneously.
If you’re in an area that already has a lot of non-natives, I’m not saying to wipe them out. You should put in the natives and then do the switchover. However, if you’re deciding to put plants in and you choose a non-native plant, you cannot contribute to native biodiversity conservation by definition, because you are putting a non-native in where there should be a native. It’s about your goals. If people like the look of non-natives, that’s not helping pollinator conservation at all.
If I could get a feeder to feed all of the bee species that are of conservation concern, butterflies, and put up feeders in people’s backyards, would I be helping? No, I wouldn’t be, because they’ve completely lost their functional role as pollinators. You can’t hope they’re going to pollinate; you have to put in the familiar native plants that they pollinate. That’s why non-natives don’t work in that capacity.
[Reed]: So, isn’t that one of the problems we’ve caused with birds by feeding them with seed and keeping them here over the Winter?
[Dr Gegear]: Absolutely! Hummingbird feeders are the worst. In every talk that I give, I give an example of a hummingbird feeder versus a hummingbird pollinating a Monarda (Bee Balm).
If you have a Monarda plant, you’ve got a host plant, seeds to feed the birds, who are eating the larva, and you’re helping a dozen species. Non-native plants do not serve as a hub for native diversity. Many birds don’t want to eat the seeds, nest in the plants, or butterflies don’t use them as host plants. There may be some exceptions, but generally, non-native plants have fewer interactions with native species.
For example, red clover has helped prevent the local extinction of Bombus fervidus (Golden Northern Bumblebee). However, when we put in native plants like Penstemon and Monarda, their numbers go up. Pollen limitation is keeping these populations suppressed. When we start to put in the natives with better pollen quality, we start to see numbers increase, which is what we would expect.
In every talk, I emphasize not to go in and just start removing all your non-natives. They’re just getting by with those non-natives. Put in the natives, and they’ll make the switch because they’re smart. They’ll decide to use the better option and then move over.
[Reed]: I serve on my town’s conservation commission, and we’ve been working on our downtown riverfront for a number of years. We’ve gotten rid of a lot of invasive plants in an area, and, as we removed the invasives, we found that other native seeds that have been there for years have come through.
[Dr Gegear]: That’s what we see. So, at Breakneck Hill in Southborough, which is one of my main sites, they worked for over two years to actively remove Loosestrife, and a huge native population of Mimulus (Monkeyflower) appeared. There’s Jewelweed, Steeplebush, Swamp Milkweed, and Swamp Rose as well. All of this came up the next year after. Get rid of the Loosestrife, and those other plants come in, with multiple bees, like the highest numbers we’ve seen at that site. So, you may have the native diversity locked on your property with an invasive species. You just don’t know it. Loosestrife is a good example, but there are others too.
[Reed]: So, what about the argument that a lot of the non-natives deter insects and bees from spending time on native plants?
[Dr Gegear]: Non-natives may be preferred, but it doesn’t mean that’s better for them. We’ve got to remember that their role as pollinators of native plants is crucial. If they’re visiting those non-natives over the natives, that’s a cost to our native plants and affects native biodiversity. We can’t think of it like we’re feeding a bunch of bees. The problem is they are pollinators and part of these pollination systems that collectively support ecosystems and wildlife. That is what we need to restore.
[Reed]: If they’re not spending time on the plants they need to, performing their job, then that’s not helping the system.
[Dr Gegear]: Exactly. Think of it like crop pollination. The number of pollinators determines how big your apple is, and how many seeds you get. The amount of bird food available and small mammal food, which then feeds predatory species, depends on how much native plants are pollinated. If those bees are spending their time on non-natives, native plants don’t get pollinated as much. We’ve got experiments showing how dependent Penstemon is on pollination to produce seeds. That’s affecting the food supply of those small mammals and birds eating the seeds, which is then affecting the food supply of predatory species, like hawks and owls that eat the birds and small mammals.
[Reed]: Yeah. I live close to Boston, and we have a massive imbalance with rabbits in the ecosystem. I use this as an example to show how we’ve slowly destroyed the predator system. There are fewer predators all as a result of poor practices, but this shows the knock-on effect when systems get out of balance.
[Dr Gegear]: Yeah. That’s a whole lot of that top-down and letting deer go and they decimate native plant communities. And rabbits too, especially in urban areas. It’s a huge problem. The coyotes are coming back. But unfortunately, they’re going after small dogs instead of rabbits, and so the public doesn’t see the benefit.
[Reed]: So, I guess my last question, getting to your plant list. I think you even call it the list. I’m sure it’s not comprehensive, but is that a list of the plants that are best for those pollinators that are endangered in the ecosystem right now?
[Dr Gegear]: Yes. And that applies to non-bumblebee bees as well. So, the key is that there are good plants for pollen and you need pollen. All bees need pollen to make new bees. The nectar is their source of fuel.
So, when you look at that list, those pollen plants like Purple-Flowering Raspberry, Meadowsweets, and another big one, St. John’s Wort. Those are key to getting those bees through. I have a bunch of butterfly data, so, we have a good sense of what butterflies use as host plants. And everybody thinks, oh, this is a great butterfly plant. Well, it turns out, just like the bees, that butterflies are picky eaters too.
Some butterflies prefer long-tube native plants for nectar. Monarda fistulosa is a very important plant when it comes to bee/butterfly species of conservation concern. There are a lot of nectar plants that, if they’ve got a long tube, will also help out the butterflies. I’d say one of the biggest ones, the Blazing Star (Liatris), is big in terms of butterfly diversity. That and Monarda, I think, are up there. The Blazing Star is visited by the long-tongue bees. It’s on the list, and I think I have it for butterflies. I have to expand out the butterfly list, I guess, is what I’m trying to say. The bee list is pretty well established.
As I get new plants and I’m able to survey them at multiple locations, things will change. Some things I thought may be important aren’t as important.
[Reed]: I appreciate your time, it’s important for people to hear what really needs to be done with our native plant systems.
[Dr Gegear]: What I tell people is: don’t trust me, put the plants in and assess it for yourself. See that you’ve made a difference.
The biggest thing is for people to understand what a pollinator is and the idea of a pollinator garden. The flower visitor vs flower pollinator is a major roadblock that we need to continue to educate people about.
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