Pollinators and Native vs. Non-native Plants

A daffodil’s visitor. Not likely that the bee is finding any nourishment

Are native plants important to the plant-pollinator communities? Sometimes I hear somebody say: “When it comes to pollinators, all flowers are the same; after all, nectars are all alike” or “my English ivy must be good for pollinators because it is teeming with insect visitors”. Such comments show a lack of information and understanding, as I mentioned in “Wildlife Food and Non-native Plants”.

I have been photographing and studying pollinators for years, and I learned long ago not to waste time looking for them in the typical suburban gardens that are the pride of many of my neighbors. Nature centers and wildflower preserves are the source of most of my photos. Flying insects rarely visit a daffodil, forsythia or a tulip. Those that do so look rather puzzled, and leave promptly without visiting similar blossoms. Roses, the fancier ones, get no visitors either. The same applies to many of the “naturalized” plants, such as lesser celandine and garlic mustard. Recently, I spent time looking for pollinators on a few non-native flowers (lesser celandines, daffodils and forsythia), knowing what the results would be. I reported some of my observations in “Of Spring Beauties and Lesser Celandines”.

A carpet of lesser celandines. Not much food for pollinators

 

In the midst of lesser celandines, a few spring beauties manage to attract their pollinators, spring beauty bees

It is true that some non-native flowers get their fair share of pollinators. Dandelions, Queen Anne’s lace and English ivy come to mind. This is not surprising in places in which the habitat has been so profoundly altered that there are no native flowers in sight. What would pollinators choose if they had options? Also, which pollinators fare better when faced only with non-native flowers? Is it only the versatile ones, the Jacks-of-all-trades? What happens to all the others? And what happens to the wildflowers that rely on native pollinators? For instance, the non-native and invasive leafy spurge (Euphorbia esula) attracts many pollinators in North Dakota. This seems to have detrimental effects on nearby native flowers.

Queen Anne’s lace attracts many insects. But, how beneficial is that to native flowers?

Doug Tallamy and his team have done extensive research on host plants for caterpillars. Over and over, native plants feed more caterpillars than non natives. There are hardly any similar systematic studies for pollinators. But we have good reasons to think that pollinators are best adapted to the flowers they co-evolved with. The North American Pollinator Protection Campaign lists some of these reasons on a factsheet.

Nectar
Nectars are not all the same (“Nectar, Breakfast of Champions”). They are a lot more than sugary water; some contain amino acids and vitamins. This cocktail makes some nectars more suitable than others for different clients. There are even those that contain a little alcohol (“Nectar. A Drink with a Zing”). Has anybody heard of tipsy bumble bees?

Pollen
Nectar isn’t the only food that flowers provide. Pollen is just as necessary, particularly for the most important pollinators, bees, also for some flower flies and a few butterflies. Adult bees may be relatively indiscriminate when it comes to nectar, but pollen for their babies is an entirely different matter. Bees tend to be more selective when it comes to pollen ranging from moderately- to highly-specialized. Some can only use pollen from one or from a handful of related species; that is why many bees are named after the flowers that are their main food source: spring beauty Andrena, azalea Andrena, squash bee, blueberry bee, rose-mallow bee, etc.

Pollinator’s equipment
Pollinators vary in shape and size and in the length of their tongue. They are well-matched to the native plants with which they have co-evolved. They may not be able to manipulate introduced plants.

Flower’s structure
Flat, open flowers may be accessible to just about any kind of visitor, but those with more complex shapes have co-evolved with their pollinators, and don’t welcome others. This is the case of kudzu, that formidable Asiatic invader. In North America, it propagates mostly through runners and rhizomes because native pollinators can’t handle its flowers, so seeds are seldom produced. In recent years, a large black bee from Asia, the giant resin bee (Megachile sculpturalis), arrived in North America by accident and started spreading across the landscape. Guess what: This bee is a very efficient pollinator of kudzu’s flowers. So, now this invasive can also propagate by seed. Oh, joy!

Flowers that have been highly modified by horticultural manipulation, whether they are introduced or native, have lost most or all the cues that guide a pollinator to its food or they have lost their nectar and pollen entirely.

My answer to the question at the head of this post is: Yes, native plants are better than non-natives when it comes to pollinators. They are part of a community that has taken eons to reach a high level of integration. This cannot be compared to the occasional use of non-native flowers by pollinators. In cases in which a non-native invasive attracts many pollinators, it may be taking pollinators away from native flowers and disrupting the normal function of the ecosystem.

Forsythia. A spectacular floral display and practically no pollinators to take advantage of it

You may want to consult the Pollinator Partnership planting guides for pollinator gardens with lists of native plants by ecoregions. Also, Urban Bee Gardens has good guides for California, although they include some non-natives.

© 2012, Beatriz Moisset. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. We have received many requests to reprint our work. Our policy is that you are free to use a short excerpt which must give proper credit to the author, and must include a link back to the original post on our site. Please use the contact form above if you have any questions.

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Comments

  1. says

    Once I began paying attention to pollinators it was a no brainer..plant natives…I am currently doing some self study to learn even more about bees…I have already planted for butterflies but want to be sure that the bees are planted for as well as other flying critters…thx for some more useful links!
    Donna@Gardens Eye View recently posted..Gardens Eye Journal-April 2012

    • says

      Honey bees are not native, as you pointed out. They are incredible generalists that visit a huge range of flowers, native and non-native, with a few exceptions. They cannot pollinate the buzz-pollinated flowers of tomatoes and other members of this family. They don’t like alfalfa flowers at all and stay away if they can help it. They are rather incompetent with other buzz-pollinated flowers such as blueberries and cranberries. They are used for these crops anyway because they can accomplish the job by sheer numbers; however the native southeastern blueberry bee (aptly named Habropoda laboriosa) can pollinate more than $25 worth of blueberries by bee.
      Beatriz Moisset recently posted..The Yucca Moth and the Yucca

  2. says

    Beatriz,

    Another terrific and succint lesson on pollinators. Thanks.

    I wasn’t aware that Kudzu previously was only able to spread vegatatively due to lack of pollinators. It’s absolutely amazing that it has been able to spread so aggressively by that means alone. I hate to think how much more invasive it’ll be with the “kudzu bee”. Dang. I hear we’ve now found it growing in our southern Ohio counties.

    Thanks again for the great articles. Each one enlightens me more and more.

    Hal
    Hal Mann recently posted..The Pony has Arrived

  3. says

    Thank you so much for leaving a comment on my blog post about Dandelions. I didn’t know they were non-native and I am trying to remove and replace non-natives with natives but it is a slow process as I am learning as I go and am not a gardener. As i drove around my neighborhood I didn’t see much for any pollinators as there aren’t many native gardens or gardens of any kind and certainly no dandelions as everyone had their lawns treated, so until I change our lawn to native, I will keep the dandelions, but I appreciate the info., I belong to Wild Ones here in western NY and am learning what is really native for this area…thank you again…Michelle…
    Rambling Woods recently posted..The Great Rambling Woods Cover-Up…

  4. says

    Beatriz, you always have an article with great information. Since learning of native plants, I started paying very close attention in my garden. I truly was amazed that the flowering shrubs planted “before I knew” are like little deserts, rarely an insect to be found. If you look around the same shrub at the natives I am allowing to restore, it is so busy with pollinator activity that it makes my head spin. You’ve affirmed my observations with this post and I appreciate reading and learning some actual facts about what transpires.

    Thanks also for the reminder that nectar is a different food than pollen. I always seem for forget about that.

    Great link to nativeplants list by ecoregion. Thanks!
    Loret recently posted..Where Are The Snakes When You Need Them?

  5. says

    Thanks for pointing out that nectars are not all the same – and that they contain more than just sugar water. Every day it is amazing to learn more and more how specialized the natural world can be and how important it is to keep every bit of it for those that need it.
    Ellen Honeycutt recently posted..A Parade of Native Azaleas

  6. Sue Sweeney says

    It’s about time someone who knew what they were talking about (e.g. you) wrote this article! Thanks very much.

  7. says

    Well as I read this post, I am thinking of the photo I just posted in “Spring!” A field of daffodils and a bright yellow forsythia (sigh). But, beneath those daffodils are a sea of violets. And cropped out of the shot is a young serviceberry tree that is just about to bloom. In the same bed as the serviceberry, further down, are two young spicebush in a blanket of wild strawberry. I am going native but I do love those daffodils and forsythia. Balance?
    thevioletfern recently posted..Spring!

  8. Sue Sweeney says

    At Scalzi Riverwalk we have a curious tall, summer-blooming plant called eastern figwort or carpenter’s square (Scrophularia marilandica). The flower openings are so tiny that only sweat bees and the like can fit inside. I often see large large wasps trying to figure it out to no avail.

    Before my area was over run with white tail deer, I think this plant was fairly common in woodlands; it now grows only where they can’t get it. (We do have about 100 in propagation, tho)

    I have always wondered why the plant would evolve this way: what benefit would it get from specializing in only the tiniest pollinators?

    • says

      Apparently the eastern figwort attracts long tongued bees and even ruby-throated hummingbirds.
      It is interesting how flowers especialize into such a variety of shapes, probably to avoid competition with others. The variety is endless.
      I am sure that I don’t need to alert you; but others may want to know that “a very similar European species (S. nodosa), has become established in New York, Massachusetts, Rhode Island, Connecticut, Pennsylvania, and New Jersey; it has a brownish-purple sterile stamen and usually finishes flowering in June” according to the University of Texas.
      Beatriz Moisset recently posted..The Yucca Moth and the Yucca

  9. says

    I read a study done in Illinois and Indiana that covered the areas of wetlands dominated by native vs. non-native plants, and the focus was on insect pollinators and insect herbivores. I will try to find the link for you. It outlined the dramatic differences in diversity and density of species, and how these differences in turn accounted for dramatic differences in many other species, such as birds, reptiles, and mammals. The changes caused a cascade, since the native insects did not use the exotic plants, so the things that ate them were also absent.

  10. says

    I have been gardening for many years and native plant gardener for two years now. But I am a novice when it comes to bees and am educating myself on their habitat needs in order to attract more native bees to our garden. We have lots of honey bees so I was wondering if non-native and native bees successfully coexist in the garden together?

Trackbacks

  1. [...] Long-flowering annuals are a bit harder to replace. Native annuals tend to reproduce a lot of seed which makes them “weedy” to most people. Tropical annuals generally either don’t set seed here or the seed needs more favorable conditions to germinate. One native annual that I love is our red sage – Salvia coccinea. This plant actually does triple duty in my yard – the insects can feed on the foliage, the hummingbirds love the flowers, and the songbirds love the seeds. Extra seedlings are easily pulled up or potted up to share with friends. If you can’t find any native annuals, at least consider choosing annuals that provide a good pollen and nectar source for pollinators – look for flower clusters made of many tiny flowers or single flowers with obvious pollen-rich centers: gazania, zinnia, heliotrope, yarrow, sunflowers, black-eyed Susan are some to consider. Think like a bee when evaluating choices. [...]

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