Interesting study: native vs. nativar( hybrid)

from Washington Post
February 27, 2024 at 6:00 a.m. EST

Natives vs. ‘Nativar’ plants: Do pollinators notice a difference?
Perspective by Tovah Martin

"Native plants are all the rage these days, and for good reason: They support regional wildlife, are adapted to the local climate and require minimal maintenance. But they don’t always fit seamlessly into a home garden setting. Although many wild plants are perfectly adapted to cultivation, natives are sometimes gangly, making them hard to weave into the average small plot.

Enter cultivars of native species — or “nativars” (a nonscientific term defined as a deliberately selected, crossbred or hybrid variation of a native species), the plant industry’s attempt to improve on nature. Given an aster with abundant quantities of sparkling blue flowers in fall, for example, they will imagine the package might look better in pink. It’s not just aesthetic changes, though; breeders also focus on creating plants that are more resistant to disease. But are these varieties equally attractive to the insects and birds who depend on them for sustenance? Researchers have been working to find the answer.

A trial at the Mt. Cuba Center in Delaware found that the bright red flowering beebalm nativar Monarda didyma, “Jacob Cline,” wildly outperformed the species in hummingbird visits. (iStock)

In 2011, Annie White was in the process of starting Nectar Landscape Design Studio when she hit a roadblock trying to find certain native species at local nurseries. To learn whether nativar substitutes would be equally efficient from a pollinator’s perspective, she dove into a PhD research program. Working with the University of Vermont, White began a field study in two Vermont locations, collecting data until 2015. She planted 11 native species paired side by side with a cultivar and then observed approximately 8,000 visits from several pollinator groups — including bumblebees, honeybees, small dark bees, beetles/bugs, butterflies/moths, flies and wasps/ants.
Her findings? “Half the time there was a preference for the native species, and half the time there was no significant difference.” Only “Lavender Towers,” a cultivar of Culver’s root (Veronicastrum virginicum), outperformed the species in pollinator visitation. On the other hand, some cultivars were noticeably snubbed by pollinators. The pink-flowering aster “Alma Potschke” bombed. “Red Grape” tradescantia also got the thumbs down.
What drove the pollinators’ preferences? White suspected that nectar quantities might play a major role. Flower color and flowering time also could be factors.

Other researchers are also looking for answers. Mt. Cuba Center in Hockessin, Del., has a trial garden (open to the public) performing comparison tests of species native to the eastern United States and their cultivars. Primarily, their studies focus on garden worthiness. But thanks to the local Pollinator Watch Team, a group of 10 to 20 trained volunteers, recent trials also collect data on pollinator action. They confirmed that pollinators prefer the natives that they have co-evolved with. “The species are always the gold standard,” says Sam Hoadley, the center’s manager of horticultural research.
In some cases, though, pollinators did gravitate to the cultivars. A trial with beebalm (monarda ) found that the bright red flowering nativar Monarda didyma , “Jacob Cline,” outperformed the species in hummingbird visits, 273 to 22. Meanwhile, the pale mauve nativar Monarda fistulosa , “Claire Grace,” also outperformed the species in moth and butterfly visits. Another surprise nativar standout was Phlox paniculata , “Jeana,” which outperformed the species “by a huge margin,” Hoadley says.
Flowering time can impact pollinator preferences. Although most nativars overlap with the species, that isn’t always the case. Some have an entirely different blooming window. Hoadley also says that management issues, such as pruning, can put any plant out of sync with its pollinators. “Delayed blooming can make them inaccessible, especially to specialist insects,” he says. And specialist insects that depend on one plant species for their survival tend to pay the price when things go out of sync. “There’s a lot of moving parts to consider,” Hoadley says.
Jen Hayes, a graduate research assistant, has been conducting a similar study at Oregon State University. She planted seven native species beside their corresponding cultivars and observed the reactions of bees, butterflies and syrphid flies over three years. Data is still being analyzed, but Hayes’s findings are similar to those of the other studies: Pollinators generally prefer the native species, and those plants also attract more specialist bees and more diverse pollinators.
All studies also confirmed what gardeners have long suspected — that the closer a nativar is to the original species, the greater the pull. Significantly altered flowers, including double echinaceas (“Pink Double Delight” in White’s study, for example) with petals in place of reproductive parts, only confuse pollinators.
Changes in a plant’s size and leaf color, on the other hand, don’t seem to affect pollinators’ interest, according to studies at Mt. Cuba. Varieties with chartreuse or variegated leaves, or more compact plants, typically performed just as well as the native plant, although caterpillar activity on shrub cultivars with red and purple leaves is still being studied."

7 Likes

I think the only exception would be pawpaw and persimmons(american cultivars, non hybrid). They have only been bred for larger fruit, and are still beneficial to insects, wildlife, and humans. The flowers and foliage are not much different than a non cultivar pawpaw or persimmon.

in not a 100% sure on this. The insects might still prefer a native or wild pawpaw. When you breed for larger fruit, sometimes as a side effect you get fewer flowers (fewer flowers leads to fewer fruit leads to lower fruitloads and thus usually bigger fruit) i can imagine this being slightly less preferable to insects…

even though the findings in the research are interesting. I’m not sure i would do a lot with them. I still plant what i find beautiful. But do value plants that fill up “flower gaps” to give insects a continues source of nectar. Luckily i prefer the species type. And i find diversity beautiful. Overal larger diversity always seems to be beneficial to insects even if a lot of the plants are not natives.

3 Likes

I doubt this research goes beyond the preliminary stage given its relative insignificance to either the fate of pollinators or the sales of ornamental plants and the two are entwined.

Tea roses are quite popular but do not seem to produce accessible nectar for pollinators. I have a few tea roses on my property- my wife especially loves the more fragrant varieties, but most of the flowering plants I grow are very popular with my pollinators and I try to keep them happy throughout the season and well into fall.

Concern about native pollinators and non-native honey bees is a growing trend. Plant breeders might be inspired to market creations devised specifically to be more nutritious for pollinators. That seems to me the only way this becomes a significant commercial pursuit that gets adequate research funding that goes beyond what is in this link. .

4 Likes

Cultivars definitely have the same or in most cases more flowers

2 Likes

Selection for lower acetogenin levels in fruit probably leads to lower levels in the foliage as well. Since zebra swallowtail caterpillars store the toxins to ward off predators, they might not get enough from the leaves of improved cultivars to protect them.

Here in California, cultivars of native plants are used a lot more than unselected natives in landscaping. The issue with this is that the state is a thousand miles long. How suitable for local wildlife is a cultivar from the extreme southern end of its range when planted in the northern part of the state? We even have species that are native to one part of the state and considered invasive in other parts of the state.

2 Likes

I’d say acetogenin breeding and even testing is only in its infancy. There’s not much data on the levels in the leaves, and I’d guess its still really high. Pawpaw cultivars are only a few generations removed from the wild.

Honestly, a topic like “impact of native vs. nativar on pollinators” is going to be so broad and multifaceted that it’s basically impossible to say anything definitive and useful one way or another. Seems like most of the time it just doesn’t really matter much, but sometimes it does for some pollinators, and sometimes it does for all pollinators. Ironically, that makes it a great research topic, because it means you just have to sift the data enough and you will get publishable results to suite the priors and bias of whichever publisher you’re using.

I mean, there are tens to hundreds of thousands of different pollinators, different natives, different natives sub-populations, different pollinator habitats, different landscape features, and billions of trillions of combinations of these. And people want some hard and fast rule about “will using sub-populations of these natives which were selected by man instead of nature be bad?” Buddy, it’s a case-by-case basis, you have to consider the impact of each plant on each species of pollinator, as well as its impact on insects and pests and its potential as cover and food source and… etc. And remember that flower color, pollen quantities, fruit and seed productivity, palatability of the leaves to bugs, the color of the leaves, their density and how much they shade, the growth habit of the plant, its root activity, its nutrient absorption, its production of particular chemicals, its water transpiration rates, etc. all have an impact on your local ecology. If you want to care about native vs. nativar, you need to think about all of these things, and measure them in great detail. Don’t plant anything until you do, and be sure to rip up any exotics and nativars you have already until we know for sure, that’s the precautionary principle in action!

Well, actually the only really clear rule is: a plant is better than no plant.

Fill your yard will plants, all kinds of different stuff. Put in trees, bushes, perennials, native, non-native, endangered, invasive, etc. It is more beneficial to have a broad diversity and a great number of plants than to have just a big patch of grass with maybe a strip of evergreens along the property line. Native vs. nativar vs. exotic is not worth spending more than 3 minutes of thinking about in most cases.

Most of the time, the alterations done by selection a cultivar just aren’t that important. We found no evidence that enhanced fruiting, leaf variegation, disease resistance, and altered growth habit degrade insect-based food webs where such plants are grown. That was a 2-year study. The only negative they could find was purple leaves were fed on less than green leaves.

Sure, sometimes it does matter. Tropical milkweed is a big flash point for that reason. Double flowers are usually poorly suited to pollinators, so plant them less. Sterile plants are tidy, but provide less food. But an invasive chinaberry will still provide more nectar pollinator than a native (wind-pollinated) sweetgum, and provides late winter berries to boot. Being exotic or being a cultivar in and of itself does not matter. Overall, the abundance and diversity of hemipteran insects does not depend on the source of the plant material per se, but rather on the particular characteristics of cultivars that distinguish them from the wild type.

There is more variation within these categories than between them. From this paper, all of the other nativars were better than either the species or cultivar of the native Kalmia. Regardless of being native, Kalmia just isn’t that useful to pollinators. But you should plant some anyway, because it does provide some benefit to pollinators. And it provides cover for birds. And it looks really pretty.

The difference between native and nativar is smaller than the differences between different species. The difference between native and exotic is smaller than the differences between native species. Some exotic species are actually better than many native species.

Some invasive exotic plants, such as honeysuckle (Lonicera maackii), may increase insect species richness and numbers by creating a more complex vegetative structure. Separately, honeysuckle was found to cause a decrease in caterpillar abundance that was moderated when there was higher tree diversity and more intact forest cover.
-State of the science and challenges of breeding landscape plants with ecological function | Horticulture Research | Oxford Academic

Honeysuckle is also an important source of browse for deer, who strongly prefer it over even most natives. In fact, in some habits at least, it makes up the primary source of food for them, and has the second highest nutritional value overall.

There is no hard and fast rule, even for plants that are extremely invasive, let alone for nativars.


At the end of the day, while there are certainly some cases when a native species would be better than a nativar, one should be very careful to not let the perfect be the enemy of the good.

8 Likes

Thanks for the variety of opinions…the beauty of this site!
I’m not a proponent of either native or nativar… though I now may pay more attention to pollinators if I have both growing side by side. Roses are certainly a great small set to explore.

:heart:

2 Likes

We must remember that “nativars” are still derived from genetics found in the native population so if a specific “nativar” is less useful to pollinators than the average of that population, it doesn’t mean that it is strictly worse than planting a non-select form. The non-select forms will vary in usefulness too with some of them equaling the level of the nativar, some worse and some better. If you really want to only plant the ones which are best for the pollinators then that will take case by case analysis of individual plants and not broad statements about whole plant categories.

2 Likes

Something I’ve always wondered about with these studies, like Mt. Cuba for example, is how much location plays a part in pollinator traffic. For an easy example, if I plant a 5 x 5 grid of flowers, and most pollinators come in from the East, then the plants on the East will likely get more traffic than the plants on the West side. If pollinators are coming from all directions, the plant in the center of the grid still isn’t as likely to get as much traffic. I know there’s a million factors in play, and there’s no way to really calculate how much influence location plays, but it still makes me wonder.

Over the last few years I’ve got a really nice population of native bees in my garden. They will all fly past anything native to get to anise hyssop. Echinaceas are 2nd in traffic, but it’s a very distant 2nd. I’ve planted anise hyssop halfway down my veggie rows to make sure I get ample bee traffic coming past my veggies when they’re in bloom. To echo what has been said above, any flowers are better than no flowers.

2 Likes

Which is made even more tricky by the fact that your local natives might not actually be the best ones to plant.

First, because the local natives are probably not the most floriferous or vigorous or beneficial. Odds are, varieties from elsewhere in the species’ range are superior. That’s just a simple probability.

Second, your local natives are probably just ok. It is largely a myth that whatever is growing locally is the most well-adapted. That can be the case, but the selective pressure of evolution, especially for non-annuals, just isn’t that fast or efficient.

To expand on the second point: Your micro-climate changed substantially in the last few decades, local ecology has changed in the last hundred years, your regional ecology has changed dramatically in the last few hundred to thousand years, and your local climate is worlds-apart from what it was ten thousand years ago. You local natives, barring a handful of very chance exceptions, have not had time to be ideally evolved. Nor does evolution usually tightly optimize. Even if your local conditions had been unchanged for a million years, evolution is unlikely to produce a perfectly adapted population. The pressure of selection between “pretty good” and “absolutely perfect” is incredibly weak, since it is very rare for growing conditions to actually allow for those slightly better traits to even express, let alone make the difference between life and death. Combine that with the high degree of statistical noise found in nature (pure DNA is not the main thing driving success, nor the second, or third, or etc…, the main thing driving success where where the bird that happened to eat the berry poops it out in a good location or onto a rock on the beach.), and the result is the vast majority of individuals in a population are not, and will never be, ideally adapted.

On top of it all, it’s in no small part ironic that there’s often less genetic diversity in planting the straight species than in planting cultivated forms and exotics. Sure, the species as a whole is more diverse in most cases (long-cultivated plants excepted), but where are you going to get those seeds? Either you are planting stuff gathered locally, in which case you’re getting a tiny sample of an often-inbred population, or you are buying from a nursery, who grow out all their plants from seed they collect off of their one mother plant, or or annuals it’s just the current batch of the handful of seeds they got, planted, collected seed from, planted, collected seed from, etc and etc, over the years resulting in a highly homogenized little population with serious founder effect going on. Perhaps in an ideal world we’d have tens of thousands of people all mailing each other seeds and cuttings of their local natives and making lots of unique, sometimes idiosyncratic, selections from those crosses. That would maximize actual genetic diversity, but it’d also be a disease vector bar none. Also kind of sounds like artificial selection. Win some lose some I guess.

1 Like

Oh yeah, for whatever reason, stuff in lamiales, like agastache, mint, lavender, and salvia, seem to really pull in the pollinators. In my garden non-native buddleja is the big winner, especially in the height of summer.

3 Likes

I agree with that wholeheartedly. Plants do adapt to where they grow, but sometimes as a matter of chance plants from other areas end up being way better adapted. If that wasn’t true we wouldn’t have invasive species.

5 Likes

thank you for sharing this