Nativars for pollinators: the truth about cross-bred native plants

Inside: If you want to plant native species for bees, you may consider nativars. But what is the difference between a nativar and a wild plant? And is it the best thing for native pollinators?

Entering a garden center in spring stirs senses that snoozed through the winter. I anticipate the wave of warmth that spills from the door, but the humidity startles me. After a winter of crispy dry air, the saturated air is hard to breathe. I pause and take a deep breath rich with the aroma of potting soil, wet concrete, sweating vegetation, and chicken manure. Suddenly, I want to move in and live beneath a potting bench.

Today, many of us visit the nursery thinking of bugs—not how to kill them but how to plant for them, protect them, make them happy and content. We want plants that produce nectar and pollen, plants with leaves that make good snacks, and plants that provide homes for our tiny companions.

In decades past, we seldom planted gardens with the idea of attracting pollinators. Not many years ago, people were hard-pressed to describe pollination, much less the creatures that do it. But now legions of gardeners, land managers, and environmentalists are trying to provide for bees, butterflies, birds, and a catchall of less familiar pollinators. Open any gardening or seed catalog and you will see choices galore.

As we wander past tables crowded with plastic pots, we wonder what is best. What kind of plant will provide the most value to the myriad animals that undertake the yearly pollination chore? How can we maximize the value of our plantings for pollinators and still maintain an attractive landscape?

Native plants for native creatures

One of the most common bits of advice is simple: Select plants that are native to the geographic region of the garden. The reason for this is compelling. The flora and fauna native to any geographic area evolved together, becoming interdependent through time. For example, some plants have evolved flower characteristics that attract certain pollinators, and those pollinators, in turn, have nutritional needs that are satisfied by those particular plants. They fit together like a lock and key, assuring each other’s survival.

Even the timing of insect emergence and flower bloom is dictated by years of coevolution in a spectacular choreography of insect and host. In some of the tightest relationships, only one pair of species is mutually suitable. More commonly, one pollinator species forages on many plant species. Luckily, if we aim to provide for those pollinators with the most specific requirements, the others can often take care of themselves. We can make the greatest impact with plantings that help those with the most explicit dependencies.

Searching for native plants

The idea of planting native plants is appealing, but the execution is a little more difficult. How do you recognize them, let alone find them?

Retailers responding to requests for native species have begun to carry both seeds and starts for gardeners. Many of these are nativars—another word for native cultivated varieties—and they have names and labels to help you learn what you are buying, what it will look like, and where it will grow. But before we get into the details of nativars, I want to step back and look at regular cultivars, the kind we have been planting for generations.

What is a cultivar?

The word cultivar is short for cultivated variety. A cultivar is a variety developed from breeding, using techniques that amplify the desired traits and suppress the annoying ones. Traditional selective breeding occurs when a plant breeder raises many plants of a single species and selects those individuals that have the characteristics the breeder is looking for. For example, as an undergraduate student, I worked for a plant breeder who was searching for alfalfa with a higher-than-average protein content.

We would grow many types of alfalfa in research plots, harvest it in the normal manner, and then perform laboratory tests to determine the amino acid profile. The following spring, we would grow seeds from the best producers in greenhouses and cross-pollinate their tiny flowers by hand—my job! Yes, I got my start in pollination ecology as a bee impersonator. Who knew?

One by one, I would collect pollen from the anthers of one flower and move it to the stigma of another, then tie a little label around each one. Each plant had a number, and I marked crosses on the tag, female first like this: 2386 x 3682. Then I would wash my hands in Lysol and prepare for the next cross.

The goal of this research was to produce enriched alfalfa cultivars for dairy cows. It was a painstaking and tedious process, but as a cash-strapped student, I was happy to have the work, even if hundreds of Lysol baths per day ruined my hands.

Today we have advanced breeding techniques

Today, modern plant breeding incorporates an array of rapidly advancing techniques from the field of molecular biology. These new tools aid with gene cloning, gene editing, and marker-assisted selections, but the principles of plant breeding remain the same.

The name of a registered cultivar—then as now—follows the scientific name. It is usually in single quotes and is not italic. For example, you might see a variety of alfalfa labeled Medicago sativa ‘Bulldog 805’, where the scientific name is followed by the cultivar name. The registrant then can sell his product under the protected name and prevent others from doing so.

The availability of native plants

Many of the cultivars for sale these days were bred from crops or flowers that have been in cultivation for decades, some for centuries. For the most part, these plants are readily familiar to us. Corn, apples, roses, and turf grasses are all sold as registered cultivars.

But when gardeners wanted to plant native plants for pollinators, a dilemma arose. How could a seller get enough native plants—or their seeds—to sell to all the people who wanted to buy them? And from a marketing point of view, how could the breeder make his plants stand apart from the others so he could make a profit?

About 20 years ago, I began seeing wild plants for sale that were harvested from plots of land that were scheduled to be cleared and developed. Native plant salvage was popular here in western Washington, where trained volunteers went into the tracts before the bulldozers and dug any plants they thought might survive the transplant process. The plants were sold by the county and the money was used for other conservation projects. I still have some wild ginger growing at home that was salvaged during that time, as well as some snowberry and cascara, two dependable pollinator plants.

Other groups, such as the Seed Savers Exchange, collected seeds from wildland plants that could be grown for restoration projects. The seeds were cultivated in greenhouses and then transplanted to selected projects.

But as the demand for wild plants outpaced the supply, salvage operations and seed saving could not possibly provide enough wild plants to satisfy everyone. Not only was it counterproductive to have scores of people trampling the wildlands in search of native plants, but if a market existed, the retailers and plant breeders wanted to fill it. This culture of shortage precipitated the nativar.

What is a nativar?

Unfortunately, what distinguishes a native variety from a cultivated variety is not clear because, by any definition, a nativar is a cultivar. All cultivated varieties began as wild types at some point in their history, so there is no real difference between them. Some biologists think the word “nativar” is a feel-good marketing term, a solution to the problem of how to supply large numbers of “native” plants to a public eager to save the bees.

In practice, a nativar is not a native plant. It has been selected, crossbred, and propagated just like any other cultivar. The selections are made by humans to appeal to humans, hoping people will buy them from a store or seed catalog. Once the nativar is perfected in the eyes of the plant breeder, he can name and register his creation by applying to the Patent and Trademark office. The process is exactly the same for nativars or cultivars.

If you find a so-called “native” plant bearing a name in single quotes following the scientific name, you can be sure it is a cultivar. It was registered so the owner can protect his investment and make money by selling his creation.

How nativars are cultivated

If there is a subtle difference between a nativar and a cultivar, it lies within the number of manipulations the plant has undergone. Certain cultivars of vegetables and garden flowers have been crossed and recrossed for decades, each one removing the plant further from its wild progenitor. Many modern fruits and vegetables are hybrids that don’t have seeds, making pollination pointless. And many flowers have so many rows of petals that pollinators cannot even find the pollen and nectar.

Most nativars on the other hand—at least for now—are closer to the original plant, having undergone fewer selections and crosses. Some nativars are not hybrids and remain open-pollinated seed-producing plants, a fact that some conservation biologists see as good and others see as bad. More on that later. Bear in mind, however, that the number of selections and crosses that go into creating a nativar is up to the breeder, there is no standard or maximum number. It’s a trade secret.

Common ways cultivars are produced

●        Selective breeding—the kind I used in alfalfa—is a common source of new cultivars. To breed selectively, a grower chooses individual plants that display the desired trait and then crosses them with each other. This type of cross has the effect of increasing the frequency of the desired gene in a population while still maintaining a fertile, openly pollinated population. For example, a breeder may search his crop for the tallest individuals, and then cross these with each other. The offspring of this cross is likely to be taller on average than the original crop.

●        Hybridization is more complex than simple selective breeding. To hybridize, breeders take genetically dissimilar individuals and cross them, producing offspring that are different from either parent. The resultant plants may be fertile or not, but the offspring of a hybrid is unlike the parents. Because the offspring are so different, the hybrid is usually cloned by vegetative reproduction, such as cuttings or tissue culture.

When you are looking at a plant label, a hybridized plant usually lists the genus name without a species name followed by an X, and then the cultivar name in single quotes. This indicates two species were crossed, and the offspring belongs to neither one. The X is simply shorthand for “cross.”

●        Backcrossing is achieved by crossing a first-generation hybrid (F1 generation) with one of its parents. It is used to produce a plant that is more similar to the original parent than the F1 hybrid, while still maintaining the desired trait that manifested in the hybrid. From a practical point of view, backcrossing can cause a substantial loss of genetic diversity even though the offspring appear similar to the parent.

●        Mutagenesis, also called mutation breeding, is a process of introducing mutations into the seeds of a plant to see what results. Although mutations can occur spontaneously in nature, laboratory mutagenesis usually involves exposing seeds to chemicals or radiation to alter the DNA. These seeds are then grown in controlled conditions, and any changes in the offspring are examined for their usefulness. Many of today’s food crops resulted from radiation treatments, including cultivars of pears, cassava, cotton, sunflowers, grapefruit, peanuts, rice, wheat, and peppermint.

●        Selections from the wild can also become a source of cultivars. In its simplest form, a breeder searches for a plant with particular traits from wild stock. When he finds one that meets his needs, he reproduces it by cloning or tissue culture.

The loss of genetic variability

All the breeding techniques listed above can result in cultivars drawn from native species, but the resultant plants contain just a small subset of all the genetic variations that exist in the original wild population. Any alleles (gene variants) not contained in the selected plants simply never appear in the offspring.

Losing genetic variability is troubling because we can’t see what’s missing. It could be something detrimental to the plant itself, like drought tolerance, disease resistance, or shade tolerance. Or it could be something that negatively affects the pollinators, such as its scent, color, or flower shape. Worse, it could be more subtle, like the pollen’s ability to provide all the necessary amino acids to the next generation of bees or butterflies.

Just because bees collect pollen doesn’t mean it’s nutritious. Honey bee foragers, for example, are known for collecting sawdust and coffee grounds, only to have it nixed by nurse bees back at the hive. But such collecting of “junk food” is a tremendous waste of time and energy for the colony. When you consider that solitary bees have only one provider collecting all the food—and no crew to reject the bad stuff—an infusion of inferior pollen could weaken or destroy the entire brood nest.

Crossing back into the wild

As I mentioned earlier, sometimes hybrids remain open-pollinated, seed-producing plants. We usually see this characteristic as a good thing because it means genetic diversity is alive and well. Variations exist among individuals, and they freely cross with one another and produce a range of genetically diverse offspring. Some alleles were lost during the selection process, but an openly pollinated, seed-producing subset is more robust than a clone.

However, not everyone agrees that an openly pollinated nativar is a good thing. They fear that the nativar, if planted near the wild types, will cross with the wild types, altering the genetics of the offspring. Because the genetics of the nativar are heavily weighted toward certain characteristics and against others, biologists fear future generations of the wild type will change to be more like the nativar.

If the nativar has a hidden negative attribute—such as low nectar or pollen production—the wild type may become less supportive of pollinators. In such a case, a nativar may become invasive, displacing a robust, pollinator-supporting plant with an inferior lookalike.

Genetic losses in the selection process

If you’ve spent much time watching pollinators in the wild, you know that many of the plants they prefer are not spectacular from a human point of view. Blooms are often small or nondescript, some so tiny you can barely see them. Sometimes you need to get down on all fours just to find the blossoms that hug the ground or open beneath a low canopy of unremarkable foliage.

Traditionally, this type of plant is difficult to sell to gardeners who are attempting to beautify their homes. For this strictly human reason, we breed nativars for flower color, size, or growth habit. If it’s “pretty” to the human eye, it is more apt to sell at the local store.

To achieve genetics that sells, the breeder chooses plants that show the desired trait and inbreeds them, often backcrossing until the trait becomes predominant. This yields what some breeders call a “slice of the gene pool” because many genes are lost in the attempt to amplify the desired ones.

Which genes are lost during selection?

Unfortunately, when we select for desired traits, we inadvertently select against other traits. Often the traits that disappear are not visible, so we may be unaware of the loss. For example, the plant may lose resistance to a particular disease, drought tolerance, or resistance to lodging (falling over in the field).

In addition, cultivars may lose their attractiveness to pollinators. They may become less attractive to pollinators or not attractive at all, or the changes may affect some pollinators but not others. Many times these negative changes may not be visible to us. Genetic changes that may affect pollinator acceptance include:

●        Alterations of flower color or structure

●        Size or arrangement of petals

●        Number of petals

●        Changes in scent

●        Variations in the rate or timing of nectar secretion

●        Changes in the sugar content of the nectar

●        Variation in the amino acid content of pollen

●        Variation in the amount of pollen

●        Bloom times

●        Height of the blooms

●        Chemical composition of the foliage

●        Water and sunlight requirements

Alterations to a plant’s DNA may have substantial effects on the biology and chemistry of a plant even if those changes are not visible to the human eye. When we select crosses to make our plant more colorful or compact, we may be changing attributes that make the pollinators just say no.

Those bad-tasting leaves

An example of an unfortunate change occurs when breeders select plants for red or purple leaf colors. These color shifts are popular among gardeners because they provide a kaleidoscope of foliage that is pleasing to the eye. But for many insects, these leaves are inedible because they are high in anthocyanins.

Although anthocyanins do not appear toxic to invertebrates, some insects avoid them, probably because of an unpleasant flavor. If a pollinator eats the leaves of the wild type but avoids the nativar, the plant is no longer beneficial as a larval host plant. In short, if you notice an unusual amount of red or purple in the leaves of a potential host, don’t use it for that purpose.

Cross-country distribution

Nationwide distribution is another problem with nativars. Sometimes they are selected, bred, and propagated in one part of the country but sold in another part. A novice gardener might not recognize that a species is not local and bring it home thinking it is native. In this scenario, it may have little value as a pollinator plant because it didn’t coevolve with the local pollinators. Local pollinators may completely ignore it.

Furthermore, the plant may not even survive in a place where the soil, climate, weather, and competing plants are all completely different. The local fauna will be influential too, including insects, birds, or mammals that may mow it down before it has a chance to establish itself.

Plant patents and the law

Controversy has always surrounded the idea of patenting plants. Those who dislike the idea believe that plants are a product of the natural world and that individuals should not have an exclusive right to control and profit from them. Those in favor of patents say that unless a plant breeder has a financial incentive for developing new plants, he has no motivation to do so. They believe that humankind will benefit if we reward a plant breeder for his creativity.

Today in the United States, two acts protect the work of plant breeders. The Plant Patent Act of 1930 allows patents to be granted for new varieties of plants that are propagated asexually. Tuber-propagated plants and sexually reproduced plants are expressly disallowed under this act. Once protection is granted, it lasts 20 years.

The second piece of legislation is the Plant Variety Protection Act of 1970. It gives breeders exclusive control over varieties that are sexually reproduced or tuber propagated. The protection lasts 20 years except for trees and vines, for which it lasts 25 years. During the protection period, the breeder has sole rights to sell, reproduce, import, or export the new variety.

How do these laws affect your purchase?

What does this mean if you are looking to buy native plants for your garden? The thing to remember is this: To get a patent, a breeder needs to prove that his plant is substantially different from those found in nature. The United States Patent and Trademark Office says, “To be patentable, the plant [must] be shown to differ from known, related plants by at least one distinguishing characteristic, which is more than a difference caused by growing conditions or fertility levels, etc.”

In other words, to get a patent on a native cultivar, the plant must be different from the wild type. The law is clear: No difference, no patent. On the other hand, the retailers who sell these plants try to convince the public that native cultivars are virtually the same as the wild type. Unfortunately, you can’t have it both ways. For those of us looking to provide for pollinators, the problem is trying to figure out whether the changes—both the ones you can see and ones you can’t—are detrimental to pollinators.

What we don’t know about new plants

Sadly, we can’t see everything we get—or don’t get—with a new cultivar. We can see obvious details like color, flower size, bloom time, and height. We can also see whether pollinators are attracted to the blooms, but we can’t easily detect nutritional and other chemical changes within the pollen, nectar, and leaves.

Research into some of the crucial questions is beginning to provide answers. Doug Tallamy at the University of Delaware has performed field trials to see what characteristics affect insect acceptance of new cultivars. He looked at changes in leaf color, leaf variegation, growth habit, disease resistance, and fruit size. Of those, the only cultivars that significantly discouraged munching insect behavior were those in which leaf color was changed from green to reds, purples, and blues. The additional colors displace chlorophyll and replace it with chemicals that are feeding deterrents.¹

Another researcher, Annie White of Nectar Landscape Design, found that multiple changes in a plant may discourage foraging, but not always. Sometimes, a pollinator may be equally responsive to a cultivar as the parent plant. But because genetic changes are complex, White believes cultivars need to be studied on a case-by-case basis.²

The work in progress at BudBurst

With so many people now planting gardens specifically for pollinators, the question of what to plant is ever more pressing. Although most ecologists agree that wild types are best, wild plants are still not readily available, and no one knows for sure how nativars compare to the real thing. So what’s a gardener do? The Chicago Botanic Garden recently stepped in to give us a hand.

The famous Chicago Botanic Garden, which opened in 1972, has an ongoing project called BudBurst. The project, led by a team of scientists, gardeners, educators, and researchers, is studying human impacts on the natural world.

One of the current programs within the BudBurst framework is focused on nativars. Begun in the spring of 2018, this citizen science project is designed to answer the question of how well nativars support pollinators compared to wild-type native plants.³

How BudBurst collects data

Participants are asked to grow wild species and their corresponding nativars close together and observe pollinator attendance at each plant. Once the flowers bloom, the participant watches the flowers once a week for ten minutes and records the number and type of visitors. They then upload their data to the BudBurst portal, where it becomes part of the permanent record to be analyzed by scientists.

The species used are perennials that grow pretty much anywhere in the United States, and participants can select ones that closely match their growing conditions. If you are not a gardener but live close to one of the partner botanic gardens, you can go there to do your observations. In addition to the Chicago Botanic Garden, you can observe pollinators at the Denver, North Carolina, and San Diego Botanic Gardens from now until the close of the observation window in fall 2022.

Gardeners may plant one or more of the cultivars along with the wild type, depending on how much space they want to allow for the project. Plants should be at least two feet apart, but close enough that they have similar growing conditions. Participants can watch multiple plants during the recording period if the plants are close enough and insect visits infrequent enough to allow it. Otherwise, they can watch each plant separately for ten minutes before moving to the next.

Learning how well nativars attract pollinators is a vital first step to determining how they affect pollinator health. If the pollinators don’t bother visiting them, an analysis of the plant’s nutritional profile isn’t necessary.

The perils of starting over

If you are thinking of starting or renovating a pollinator area, take the time to make a well-informed plan. Experienced native gardeners and even restoration ecologists warn us against removing all non-native species from a plot and starting over. A mix of native and non-native species is perfectly fine and, in some cases, a mix can be preferable to pulling every weed.

Susan Waters of Quamish EcoResearch in Olympia, Washington explained that certain weeds may be supporting some of the bee species, especially those weeds that bloom when other flowers are scarce. “Be careful about what you eliminate,” she says and recommends replacing weedy species with similar things that bloom at roughly the same time.⁴

A good example is Hypochaeris radicata, also known as hairy cat’s ear, false dandelion, and flatweed. Not only is it nearly impossible to eliminate, but it’s popular among a wide range of pollinators. To avoid disrupting the bees that depend on it, remove it gradually and only after alternative floral resources become established.

Landscape architect Melissa Reavis of New York’s Hollander Design echoed this same philosophy. “You don’t have to start over. Just introduce a few new native species into your beds. Plant some natives in with those roses and peonies that you love, and the insects will come.”⁵

Other tips for pollinator habitat

The bottom line is biodiversity. The more species that live in your garden, the healthier the ecosystem. A diverse garden—even one that includes some less desirable species—will ultimately have fewer pests. To some extent, all these creatures eat each other—a practice that keeps everyone in check. Don’t worry when you see a robber fly snatching a sweat bee, or a yellowjacket taking off with a caterpillar. That so-called balance of nature is a sure sign of garden health.

Best practices for keeping a “pretty-much” native garden

●        Do your homework to learn where the parent plant of a nativar originated. Retail chains may be shipping their products throughout the country, so it’s up to you to decide if your purchase is native to your area or not.

●        Avoid plants that have been bred to have purple or reddish leaves. Although they may be fine for some species, they may not be as useful as less manipulated selections. Even leaves with green and white variegations are less nutritious than plain green ones.

●        Plan your garden so something is in bloom from spring through fall. Just as you prefer to eat every day, so do your pollinators. And remember, those weeds you grudgingly leave in place can help carry your pollinators through a rough patch.

●        Don’t forget to underplant your trees with shade-tolerant species. Not every plant thrives in the bright sun, and those shady plants attract their own set of pollinators.

●        Provide safe areas for insects to drink fresh water. If you live in mosquito country, keep the water’s surface moving with a waterfall or bubbler.

●        Forget the pesticides. Toxic chemicals have no place in a pollinator garden.

●        A sprinkling of nest boxes is fine for cavity-nesting bees, but avoid massive structures with thousands of holes. Too many individual bees living close together can attract bumper crops of parasites and predators. A few smaller nest boxes, widely spaced, are better than one large one.

●        Think beyond nectar and pollen. If you are too much of a neatnik, compulsively dead-heading a bloom as soon as it softens, you will rob the birds of nutritious seeds. If you cover every square inch of ground with mulch, you will deny the ground-nesting bees a safe place to live.

●        And don’t forget the humans. If you fail to leave enough space for a game of chess or reading a book, you lose many of your garden pleasures. Small patches of lawn, a rope swing, a park bench, a hammock strung between trees are all perches where you can watch all the precious creatures you worked so hard to attract.

Asking the right questions

In an ideal world, we could buy all the wild-type plants we desired to attract the creatures we love. But our real world is complex, and at times we may be forced to settle for nativars instead of the real thing.

Rather than be discouraged, realize we’re riding a learning curve. The fact that we are asking questions like “What’s a nativar?” means we’ve come a long way to better understanding the forces that affect our environment.

Once we understand the difference between natives and nativars, we can use scientific knowledge to make gardening choices. Even though the available plants may not be ideal, we are finally driving our own train, making decisions that will work best for us individually, and buying based on fact rather than marketing hype.

Rusty
Honey Bee Suite

Reference

1. Tallamy DW and Darke R. 2009. Bringing Nature Home: How You Can Sustain Wildlife with Native Plants. Timber Press, Portland, OR.
2. White, AS. 2016. “From Nursery to Nature: Are native cultivars as valuable to pollinators as native species?” PollinatorGardens.org. https://pollinatorgardens.org/2013/02/08/my-research/ Retrieved April 10, 2021.
3. BudBurst.org. 2017. “Help us monitor pollinator visits to native species and their cultivars.” Nativars Research Project. https://budburst.org/nativars. Retrieved March 23, 2021.
4. Waters, S. 2021. Quamish EcoResearch. “How do plant-pollinator communities respond to restoration?” https://www.quamasheco.com/networks-and-restoration Retrieved March 25, 2021.
5. Marcoux, S. 2021. “Here’s Why Every Garden Needs Pollinators—and Design-Centric Ways to Get Them There.” Veranda.com https://www.veranda.com/outdoor-garden/a35815974/pollinator-garden/# Retrieved April 24, 2021.