A Deep Dive into Pollinators
6/27/2023 3:12 pm
A Deep Dive into Pollinators
June is National Pollinators Month. That means it is time for a deep dive into pollinators. How much do you know about pollinators? Do the facts line up with what you think you know?
Below, just for the sake of knowledge, I'll examine which the best pollinators actually are. We can be assured people will continue to favor the "pretty" pollinators regardless of their actual importance. Does it matter? Probably not much, since many plants have multiple pollinators, though not all. Some fascinating plants only have one pollinator.
BUTTERFLIES AS POLLINATORS
Swallowtail on Roadside Verbena bonariensis
Monarchs get more attention than other butterflies. In part that is due to their beauty, but my botanist sister's take is that as butterflies go they are unique in other ways that fascinate humans. Their life cycle is much longer than other butterflies and they make amazing journeys across great distances every year. Having failed multiple times to successfully grow milkweed, probably due to my limited full sun areas, I persist trying anyway, succumbing to the annual media pressure to "plant for the monarchs." This year I've managed to keep two large Asclepias tuberosa divisions from a friend alive and await buds on a Asclepias incarnata planted last year in hopes of doing my part in helping these beautiful creatures on their long journey.
I suspect that you, like me, constantly see garden articles and Facebook posts urging folks to plant for monarchs and other butterflies as "pollinators." The question obscured in these urgings is whether monarchs or butterflies actually are of great importance as pollinators? Turns out the answer is "no." Butterflies are far less efficient than bees at moving pollen between plants. Highly perched on their long thin legs, they do not pick up much pollen on their bodies and lack specialized structures for collecting it. (U.S.D.A. Forest Service)
What about all that literature out there emphasizing butterflies as pollinators? "[S]ome scientists, journalists and conservationists go further, claiming that butterflies are essential pollinators, and that the productivity of agricultural crops and native plants would plummet if their populations drop. Whether prompted by naiveté or by calculation, however, the invocation of pollination as a motivation to conserve butterflies misrepresents the best science available. It amounts to false advertising." Scientific American. Indeed, it turns out that Monarchs are particularly poor pollinators (and that includes of milkweed plants upon which their young rely). Scientific American.
In sum, butterflies are beautiful and that makes humans plant for them. They do some pollination, but planting for butterflies as "pollinators" is not all it is cracked up to be. Nevertheless, a healthy quantity of butterflies is not only a delight to human senses, it is also an indicator of a healthy garden ecosystem. If butterflies are flourishing, chances are our best pollinators -- bees -- are too. So keep on planting for butterflies, because you are planting for pollinators, just maybe not the ones you thought you were - a win/win proposition!
BEES - OUR BEST POLLINATORS
Bee on Papaver somniforum
Bees, on the other hand, are the lifeline to plants. Whether it is the imported European honey bees that are essential to crop production or the wild bees who, for the most part lead a more solitary life, bees are critical to plant and human survival.
"While more than three quarters of the world’s crops and flowering plants, whether wild or cultivated for human food or ornamentation, are pollinated by animals—it is primarily by wild and domesticated bees. The much-publicized declines in bee populations because of parasites, diseases, pesticides, habitat loss and climate change indeed may threaten economic systems and food production". Scientific American.
Honey bees are a special case, brought here in the early 1600's for the purpose of crop production. They are specifically raised and managed for crop production, but over time have. become more common in backyard hives (both managed ones and ones of their own making). A great deal of warranted fuss is made over saving honey bees because without them, our food crops would be in dire straits.
Are honey bees the best of pollinators? Let's just say that they are the most effective pollinators for agricultural production because of the nature of their hives. Loads of bees can be boxed and placed where they can pollinate crops. Wild bees live very differently than honeybees. Many are solitary or colonize in a way that can't be easily controlled or transported for crop production like honey bees.
Wild bees are better at the act of pollination, even if not as effective as honey bees. One reason is that they are active in cooler and cloudier conditions than honey bees, so they forage earlier in the year as well as earlier in the morning and later into the afternoon. Penn State Extension. This makes native bees great at supplementing crop pollination. Bumble Bees as Pollinators.
There are about 4,000 species of native bees in the U.S. It is estimated that upwards of 25% of native bees are feeding specialists and could not survive without specific families of plants in our environment. These plants range from squash, cherries, to violas, blueberries, asters, fleabane and a host of others. Eastern Native Bee Hosts. (Beware drawing the false assumption that native bees who are specialist feeders require native plants in those specific families, however. Native bees happily feed upon non-native plants in those families, such as Japanese asters. Plant families can be large and contain many species found around the globe.)
A point of interest about all bees, imported honey bees and wild (except bumble bees) is that they fly only about 100 yards from their nesting habitat. Wild bees nest in various ways: ground nesting, tunnels, and annoyingly, your wooden deck posts. Some wild bees are solitary; others nest in groups. To encourage wild bees to live within your 100 yard radius, leave some ground exposed and avoid rubber mulch for ground nesters. For tunnelers and cavity nesting bees, you can leave stumps, brush piles, plant stems, and pithy stems around. Think of this as permission to be messier in the garden for a good cause.
Bumble bees are colonizing ground nesters, generally preferring open fields, beneath old tree stumps and abandoned rodent nests. Generally considered a gentle bee, disturbing a nest of bumble bees is akin to disturbing a yellow jacket nest. Bumble bees turn out to be great greenhouse pollinators for tomatoes, sweet peppers and strawberries and a good alternative to hand pollination -- if you can convince workers the danger of being stung is small. Bumble Bees as Pollinators.
In addition to leaving some mess for our native bees, the other important thing we can do to help these creatures help us and our plants is to minimize outside pesticide use, especialy spraying yards for mosquitoes. Penn State Extension. Reject claims that there are "mosquito" specific sprays. There aren't any on the market. Mosquito spraying kills loads of insects and is only a short term solution for mosquitoes (interrupting just one life cycle of mosquitoes). Mosquito Spray Kills Bees
Moths present a special case as pollinators. They largely feed at night. Many plants have evolved to open late in the afternoon or night and release fragrance at night to attract moths to pollinate. The nectar is often deeply hidden in these plants, requiring deep penetration by the probiscus of the moth.
Many moth pollinated plants are white or have flowers which grow in clusters that provide landing platforms. Plants pollinated by moths include yucca, gardenia, liatris, night blooming cereus, Camassia, and Darwin's orchid (Angraecum sesquipedale). Darwin's orchid is pollinated by the Madagascan hawkmoth, which sports an absurdly long probiscus - eleven inches long! USDA; The Guardian. A recent study has even concluded that moths are better at pollinating than bees generally. Sussex Study
Indeed, ongoing research suggests that moths are the "unsung heroes" of the pollinator world. Recently it was discovered that moths pollinate red clover, not just bees. Smithsonian
Wondering why moths are better pollinators than butterflies? Moths are generally shorter, fatter and most importantly the majority have furry/fuzzy bodies. This fur -- just like the bodies of bees -- carries and deposits pollen as moths feed. How Stuff Works. Moths turn out to be pollinators of crops too: strawberries, peaches, apples, pears, beans and peas. Further study of moths may well show that moths are far more important in crop production than their reputations as pests suggests. How Stuff Works.
Jack-in-the-Pulpits are fly pollinated along with many stinky plants in the Aroid family like Voodoo Lily (Sauromatum venosum), Amorphophallus, and Arums.
But flies pollinate more than "stinky plants. Indeed, more than 100 cultivated crops are regularly visited by flies and depend largely on fly pollination for abundant fruit set and seed production. A large number of wild food plants, numerous medicinal plants and cultivated garden plants are aided from fly pollination as well. This includes Cacao, source of chocolate. UCANR. It also includes pears, apples, strawberries, cherries, plums, apricots, peaches, rowanberries, raspberries, blackberries, roses, mangoes, fennel, coriander, caraway, kitchen onions, parsley, carrots, and many more. UCANR.
There are over 160,000 species of flies. In some harsh environments, like arctic and alpine where there is reduced bee activity due to conditions, flies are of critical importance to certain forms of plant life. UCANR.
Beetles are essential pollinators often referred to as "messy pollinators" since they often chew through leaves and petals. Still, without beetle pollination, we'd likely be without some of our favorite southern plants.
Beetles are among the Earth's oldest pollinators too. Many of the plants pollinated by beetles are described as spicy, musky, yeasty, rotten or fermented smelling. Beetle pollinated plants include Calycanthus, Spicebush (Lindera), and Magnolia. Some beetles are generalists, while others are specialists feeders (water lilies, custard apples etc.) Unlike other pollinators, beetles don't visit flowers to eat nectar. They eat pollen (and often flowers and leaves too). UMD
Bats do their pollinating in the dark of night. They prefer large flowers which are often bell shaped. This includes bananas, mangoes, guavas, and agaves. Bat Pollination
The dreaded yellow-jackets do have some pollinator value, but there are other wasps of greater pollinator importance. Wild Figs need to be pollinated by fig moths, which are in fact a wasp; these wasps have evolved to live inside figs and feed exclusively on them. Figs and Wasps: How Are Figs Pollinated. After reading the linked article, you will know how why some vegans avoid figs, especial wild grown ones. As a general rule, however, wasps are not very efficient pollinators, lacking the fuzzy bodies of their relatives, the bees, also in the Hymenoptera group.
LIZARDS & SKINKS
There is not a lot of data on these in the US, but in the tropics pollination by lizards and skinks has been verified. Reptiles As Pollinators.
Ants are classified as minor pollinators, highly ineffective at the job despite the great number of plants they visit. They are more nectar robbers than pollinators. Ants as Pollinators
About 2,000 species of birds assist with pollination of different plants. Bird pollination is most common in tropical areas where birds are more abundant. In areas where insects are scarce, birds may also be critical pollinators. Birds that participate in pollination to some degree include: honeycreepers, honeyeaters, hummingbirds, orioles, parrots, spiderhunters, sugarbirds, sunbirds and white-eyes. Bird Pollinators
There are questions about how humans feeding birds affects their biology as well value as pollinators. In a multi-year Costa Rican study about hummingbirds, it was found that the use of artificial sugar-water feeders influenced the quantity and composition of pollen loads of highland hummers. "Sugar-water feeders congregate hummingbirds drawing them away from flowers." The uptake? "The competitive and antagonistic pattern observed between feeders and flowers shows that natural pollination systems are being significantly altered by the use of feeders. Supplementing hummingbirds with food seems likely to interfere with pollination networks already stressed by many anthropogenic effects, including global warming." Costa Rican Hummingbird Study.
So consider planting close to your windows or porch for hummingbirds as an alternative to sugar water feeding. Humans feeding hummers may be killing them with kindness anyway. To Feed Or Not To Feed
THE REST OF THE POLLINATORS
Cockroaches and male mosquitoes (which don't feed on blood, but nectar) are also pollinators. Add to the roster, spiders, lemurs, rodents, mongooses and honey possums. Their significance as pollinators is not considered major, however. Unsung Pollinators.
We are all guilty of speciesism based on our own preferences. Bluebirds get special houses not because they are particularly important or wonderful birds, but because a vast majority of folks' favorite color is blue, which makes bluebirds seem prettier than other birds to many.Once my mother's neighbor approached to alert her that wrens had taken up residence in her bluebird house. Mom's response: "They need to nest too. Let them have it." Speciesism plays into our planting for pollinators too -- planting for the monarchs, hummingbirds etc. Who amongst us plants for flies, after all?
In the end, so long as we plant a diversity of flowering things and minimize outdoor pesticide spraying, a robust ecosystem of bees, birds, butterflies and insects will assure pollination of most plants. Everyone can tend to their favorites, whether one grows milkweeds for monarchs or one grows voodoo lilies for the blooms, which happen to bring the flies. A garden full of bees, insects, moths, butterflies and birds assures the continuation of plant life in general, although it also may mean tolerating some chewed up leaves and disappearing fruit too.
Contributed by Liane Schleifer