When Urban Pollinator Gardens Meet Native Plant Communities

Public concern about the state of bees and other pollinating insects has led to increased interest in pollinator gardens. Planting a pollinator garden is often promoted as an excellent way for the average person to help protect pollinators. And it is! However, as with anything in life, there can be downsides.

In many urban areas, populations of native plants remain on undeveloped or abandoned land, in parks or reserves, or simply as part of the developed landscape. Urban areas may also share borders with natural areas, the edges of which are particularly prone to invasions by non-native plants. Due to human activity and habitat fragmentation, many native plant populations are now threatened. Urban areas are home to the last remaining populations of some of these plants.

Concern for native plant populations in and around urban areas prompted researchers at University of Pittsburgh to review some of the impacts that urban pollinator gardens may have and to develop a “roadmap for research” going forward. Their report was published earlier this year in New Phytologist.

Planting a wildflower seed mix is a simple way to establish a pollinator garden, and such mixes are sold commercially for this purpose. Governmental and non-governmental organizations also issue recommendations for wildflower, pollinator, or meadow seed mixes. With this in mind, the researchers selected 30 seed mixes “targeted for urban settings in the northeastern or mid-Atlantic USA” to determine what species are being recommended for or commonly planted in pollinator gardens in this region. They also developed a “species impact index” to assess “the likelihood a species would impact remnant wild urban plant populations.”

A total of 230 species were represented in the 30 seed mixes. The researchers selected the 45 most common species for evaluation. Most of these species (75%) have generalized pollination systems, suggesting that there is potential for sharing pollinators with remnant native plants. Two-thirds of the species had native ranges that overlapped with the targeted region; however, the remaining one-third originated from Europe or western North America. The native species all had “generalized pollination systems, strong dispersal and colonization ability, and broad environmental tolerances,” all traits that could have “high impacts” either directly or indirectly on remnant native plants. Other species were found to have either high dispersal ability but low chance of survival or low dispersal ability but high chance of survival.

This led the researchers to conclude that “the majority of planted wildflower species have a high potential to interact with native species via pollinators but also have the ability to disperse and survive outside of the garden.” Sharing pollinators is especially likely due to super-generalists like the honeybee, which “utilizes flowers from many habitat types.” Considering this, the researchers outlined “four pollinator-mediated interactions that can affect remnant native plants and their communities,” including how these interactions can be exacerbated when wildflower species escape gardens and invade remnant plant communities.

photo credit: wikimedia commons

The first interaction involves the quantity of pollinator visits. The concern is that native plants may be “outcompeted for pollinators” due to the “dense, high-resource displays” of pollinator gardens. Whether pollinator visits will increase or decrease depends on many things, including the location of the gardens and their proximity to native plant communities. Pollinator sharing between the two has been observed; however, “the consequences of this for effective pollination of natives are not yet understood.”

The second interaction involves the quality of pollinator visits. Because pollinators are shared between native plant communities and pollinator gardens, there is a risk that the pollen from one species will be transferred to another species. High quantities of this “heterospecific pollen” can result in reduced seed production. “Low-quality pollination in terms of heterospecific pollen from wildflower plantings may be especially detrimental for wild remnant species.”

The third interaction involves gene flow between pollinator gardens and native plant communities. Pollen that is transferred from closely related species (or even individuals of the same species but from a different location) can have undesired consequences. In some cases, it can increase genetic variation and help address problems associated with inbreeding depression. In other cases, it can introduce traits that are detrimental to native plant populations, particularly traits that disrupt adaptations that are beneficial to surviving in urban environments, like seed dispersal and flowering time. Whether gene flow between the two groups will be positive or negative is difficult to predict, and “the likelihood of genetic extinction versus genetic rescue will depend on remnant population size, genetic diversity, and degree of urban adaptation relative to the planted wildflowers.”

The fourth interaction involves pathogen transmission via shared pollinators. “Both bacterial and viral pathogens can be transmitted via pollen, and bacterial pathogens can be passed from one pollinator to another.” In this way, pollinators can act as “hubs for pathogen exchange,” which is especially concerning when the diseases being transmitted are ones for which the native plants have not adapted defenses.

photo credit: wikimedia commons

All of these interactions become more direct once wildflowers escape gardens and establish themselves among the native plants. And because the species in wildflower seed mixes are selected for their tolerance of urban conditions, “they may be particularly strong competitors with wild remnant populations,” outcompeting them for space and resources. On the other hand, the authors note that, depending on the species, they may also “provide biotic resistance to more noxious invaders.”

All of these interactions require further investigation. In their conclusion, the authors affirm, “While there is a clear potential for positive effects of urban wildflower plantings on remnant plant biodiversity, there is also a strong likelihood for unintended consequences.” They then suggest future research topics that will help us answer many of these questions. In the meantime, pollinator gardens should not be discouraged, but the plants (and their origins) should be carefully considered. One place to start is with wildflower seed mixes, which can be ‘fine-tuned’ so that they benefit our urban pollinators as well as our remnant native plants. Read more about plant selection for pollinators here.


Field Trip: Chico Hot Springs and Yellowstone National Park

Thanks to an invitation from my girlfriend Sierra and her family, I spent the first weekend in May exploring Yellowstone National Park by way of Chico Hot Springs in Pray, Montana. The weather was perfect, and there were more plants in bloom than I had expected. During our hikes, my eyes were practically glued to the ground looking for both familiar and unfamiliar plant life. Most of the plants in bloom were short and easily overlooked. Many were non-native. Regardless, the amateur botanist in me was thrilled to be able to spend time with each one, whether I was able to identify it or not. I tried to remind myself to look up as often as I was looking down. Both views were remarkable.

On our first day there, we hiked in the hills above Chico Hot Springs. The trail brought us to a place called Trout Pond. There were lots of little plants to see along the way.

Trout Pond (a.k.a. Chico Pond) near Chico Hot Springs in Pray, Montana

mountain bluebells (Mertensia longifolia)

shooting star (Dodecantheon pulchellum)

western stoneseed (Lithospermum ruderale)

western wallflower (Erysimum capitatum)

The next day we drove into Yellowstone. From the north entrance we headed east towards Lamar Valley. Wildlife viewing was plentiful. Elk, bison, bighorn sheep, pronghorn, black bears, red foxes, and even – if you can believe it – Canada geese.

Sierra looks through the binoculars.

Perhaps she was looking for this red-tailed hawk.

Daniel looks at a tiny plant growing in the rocks.

Still not sure what this tiny plant is…

On our third day there, we headed south to see some geysers. We made it to the Norris Geyser Basin and then decided to head east to see the Grand Canyon of the Yellowstone. This was our geology leg of the tour. But that doesn’t mean we didn’t stop to look at a plant or two along the way.

Nuttall’s violet (Viola nuttallii) near the petrified tree in Yellowstone National Park

Wild strawberry (Fragaria sp.) at Norris Geyser Basin in Yellowstone National Park


Photos of Lamar Valley, red-tailed hawk, Daniel looking at a tiny plant, mystery plant, and Grand Canyon of the Yellowstone were taken by Sierra Laverty. The rest were taken by Daniel Murphy.

Speaking of Sierra, she is the founder and keeper of Awkward Botany’s Facebook page and Instagram account. Please check them out and like, follow, etc. for Awkward Botany extras.

What’s in a Packet of Wildflower Seeds? – An Introduction

Occasionally I receive packets of wildflower seeds from companies that are not in the business of growing plants. They are promotional items – encouraging people to plant flowers while simultaneously marketing their wares. Often the seed packet lacks a list of the seeds included in the mix, and so it remains unclear what “wildflowers” are actually in there. My guess is that most seed packets like this go unplanted, and those that do get planted, may go uncared for. After all, the company that supplied them isn’t all that concerned about what gets done with them anyway.

As it is, generic packets of wildflower seeds like this may not actually contain any wildflower seeds. The term wildflower generally refers to a flowering plant that grows in the wild and was not intentionally planted by humans. It is synonymous with native plant, but it can also refer to non-native plants that have become naturalized. By this definition, a packet of wildflower seeds should only include seeds of native or naturalized plants and should not include horticultural selections, hybrids, or cultivated varieties. Ideally, the seed mix would be specific to a particular region, as each region throughout the world has its own suite of native wildflowers.

With that in my mind, I was immediately curious about an unlabeled packet of wildflower seeds I recently received as a promotional item from a company that has nothing to do with plants. This is a company that ships items nationwide and around the world, which leads me to believe that hundreds of people received similar packets of seeds around the same time I did. The seed packet is not labeled for a particular region, so all of us likely received a similar mix of seeds. “Wildflowers” then, at least in this case, means a random assortment of flowering plants with questionable provenance and no sense of geographic location.

The seed packet in question.

The seed packet in question.

Curiousity is killing me; so I am determined to find out what is in this mysterious packet of seeds. Using a pair of magnifying glasses, I seperated the seeds into 26 groups. Each group, from as best as I can tell, should be a unique species (or at least from the same genus). The next step will be to grow the seeds out and see what they actually are. I have limited space and time, so this is going to take a while. Since “wildflower” is not an exact term, I have decided that in order to be considered a wildflower the plant will have to be native to North America. (I should probably say western North America or Intermountain West, since that is where I am located, but that’s pushing it.)

The amount of seeds that each of the 26 groups consists of varies greatly, from a single seed to 52 seeds. Some of the seeds may not be viable, and some of the seedlings are sure to perish along the way. Despite losses, it should be clear in the end what this packet of seeds mainly consists of and whether or not it is indeed a wildflower seed mix. If I were skilled at identifying species simply by observing their seeds, I might be able to avoid growing them out, but I am not confident enough to do that. However, one group of seeds is almost certainly calendula. Calendula is a genus native to parts of Asia, Europe, and North Africa that has been introduced to North America. So, we’re already off to a bad start.

seed packets_experiment

To be clear, I have no intention of disclosing or calling out the company that sent the seeds. This is all in good fun. No hard feelings. I’m satisfying my own curiosity, and perhaps yours, too. Until the next update (which could be a while), go run through a field of wildflowers. Enjoy yourself.


The Nippleworts of Camassia Natural Area

This is a guest post. Words and illustration by Mesquite Cervino.

At the end of a residential neighborhood that is barely off the 205 in the hills of West Linn, Oregon is a small, 26 acre preserve called the Camassia Natural Area. The defining features of the landscape were caused by the Missoula Floods (aka the Spokane or Bretz floods) at the end of the last ice age (12 to 19 thousand years ago) which swept away the already established soil and in their place deposited glacial erratics from other far-away places, some even coming all the way from Canada. The flood reached eastern Oregon and the Willamette via the Columbia River Gorge and created the green and rocky plateau that is now Camassia.

While the reserve is named after a widespread plant in the park, which is a common camas (Camassia quamash) that blooms in April and early May, the park has over 300 different species overall. However, one species in particular has kicked in the door and far overstayed its welcome in the park, becoming a highly invasive weed in the area. This plant is known as Lapsana communis or nipplewort. It is an annual dicot that is native to Europe and Asia, but is considered invasive in Canada and the United States. In the U.S., the weed is most common west of the Cascades in the Pacific Northwest. It is in the Asteraceae family (aka the aster, daisy, or sunflower family), and like dandelions or common groundsel, nipplewort is part of the weedy side of the family.

nicole illustration_cropped

The name itself has an interesting history that originated around 350 years ago when an Englishman by the name of John Parkinson named the plant after he heard that it was useful for topical treatment of ulcers for women on certain areas of their bodies. It was also an herbal treatment for nursing mothers, and was used to aid cows and goats that were having trouble being milked. Another source of the name is said to have come from the shape of the basal lobes and their resembling features. Because nipplewort is edible, its leaves can be cooked like spinach or served raw in only the most hipster of salads.

In terms of its anatomy, nipplewort is about one to three and a half inches in height, has alternate, ovular, lobed, rich green leaves, and composite yellow flowers with about 13 petals similar in resemblance to a dandelion. They flower from June to September and are pollinated by various insects. Seed set occurs in July to October. The plant then spreads through reseeding, and one plant can produce 400 to 1,000 seeds that put out shoots in fall and spring.

Consult a fellow botanist to find out more about Lapsana communis, especially if you are curious to know if it has invaded your territory. If it has, consider entertaining dinner guests with this unusual plant.

Additional Resources:


Field Trip: Mud Springs Ridge and Cow Creek Saddle

Last weekend I went on two all day field trips that were part of Idaho Native Plant Society‘s annual meeting. The second field trip was in a location with a climate considerably warmer and drier than the first field trip. The flora was much more familiar to me since it was similar to what I generally see in southern Idaho. We visited two sites: Mud Springs Ridge and Cow Creek Saddle. Both are high on a mountain ridge (around 5300 feet in elevation) flanked by the Salmon River canyon on the east and the Snake River canyon on the west. The tiny town of Lucile, Idaho was just below us to the east, and if we would have continued down the other side of the mountain, we would have arrived at Hells Canyon National Recreation Area. These sites are high elevation grasslands, and there was a huge diversity of grasses and forbs to explore.

Taking decent photos of the plants was a challenge as the sun was shining brightly and there was a constant breeze. Photographs don’t quite cut it anyway. The views were incredible. Standing on a ridge top peering across a meadow full of wildflowers with more mountains in the distance. Mass amounts of lupines and paintbrushes mixed with grasses and other plants being tossed about in the breeze. Little rock gardens randomly dispersed across the hillsides. You kind of had to be there.

A view across the meadow at Mud Springs Ridge

A view across the meadow at Mud Springs Ridge

Searching for Silene spaldingii - an Idaho endemic - on the mountainside

Fellow botany geeks searching for Silene spaldingii (Spalding’s catchfly) – a rare, imperiled plant species

Gnarly, old curl-leaf mountain mahogany (Cercocarpus ledifolius) growing out of a rock outcrop

Gnarly, old Cercocapus ledifolius (curl-leaf mountain mahogany) growing out of a rock outcrop

Close up of Cercocarpus ledifolius

Cercocarpus ledifolius (curl-leaf mountain mahogany)

Orthocarpus tenuifolius (owl's clover)

Orthocarpus tenuifolius (thin-leaved owl’s clover)

Castilleja (indian paintbrush)

Castilleja hispida (harsh paintbrush)

Castilleja cusickii (Cusick's paintbrush)

Castilleja cusickii (Cusick’s paintbrush)

Lewissia columbiana v. wallowaensis

Lewisia columbiana var. wallowensis (Wallowa lewisia)

Lewissia columbiana v. wallowaensis

Lewisia columbiana var. wallowensis (Wallowa lewisia)


Erigeron davisii (Davis’ fleabane)

On cow creek saddle looking towards Salmon River canyon

On Cow Creek Saddle looking towards Salmon River canyon

On cow creek saddle looking towards Snake River canyon

On Cow Creek Saddle looking towards Snake River canyon

The field trips were incredible, and the annual meeting in general was a lot of fun. If you have a native plant society in your neck of the woods and you are not already a member, I highly recommend checking it out. Now, where to next?


Field Trip: Coolwater Ridge Lookout

I spent this past weekend camping with friends near Grangeville, Idaho. I was attending the annual meeting of the Idaho Native Plant Society. Meetings in the boring sense of the word occurred, but they were brief. The bulk of the weekend consisted of long hikes on guided field trips. This post is a pictorial tour of a small fraction of the plants I saw on the Coolwater Ridge Lookout trail which is located in the Bitterroot Mountains  – my first of two all-day field trips. From where we were hiking we could look down at the canyon where the Selway River was fixing to meet the Lochsa River to form the middle fork of the Clearwater River. This is a part of Idaho that is basically too beautiful for words. At some point I will have more to say about this particular location, but for now here are a handful of semi-decent photos I took while on the hike.

A view from Coolwater Ridge Lookout trail. Looking down at the Selway River Canyon.

A view from Coolwater Ridge. Looking down at the Selway River canyon.

Erythronium grandiflorum - yellow glacier lily

Erythronium grandiflorum – yellow glacier lily

Leptosiphon nuttallii - Nuttall's linanthus

Leptosiphon nuttallii – Nuttall’s linanthus

Polemonium pulcherrimum - Jacob's-ladder

Polemonium pulcherrimum – Jacob’s-ladder

A view from the ridge. Looking down at the Selway River Canyon.

Sambucus racemosa – red elderberry

Phlox diffua - spreading phlox

Phlox diffusa – spreading phlox

Ribes viscosissimum - sticky currant

Ribes viscosissimum – sticky currant

Senecio integerrimus var. exaltatutus - Columbia groundsel

Senecio integerrimus var. exaltatutus – Columbia groundsel

Synthyris platycarpa - kittentails

Synthyris platycarpa – Idaho kittentails

Vaccinium scoparium - whortleberry

Vaccinium scoparium – grouse whortleberry

Viola glabella - pioneer violet

Viola glabella – pioneer violet

Cheilanthes feei - Fee's lipfern

Cheilanthes feei – Fee’s lipfern

Stay tuned for photos from the second of two field trips. In the meantime, go outside and see some nature.


Year of Pollination: Scarlet Gilia and Its Pollinators

Flowers that are visited and/or pollinated by hummingbirds typically fit the following description: petals are brightly colored, often red; petals are fused to form a long, narrow tube; a “landing pad” is absent; abundant nectar is produced deep within the flower; and fragrance is weak or nonexistent. Scarlet gilia (Ipomopsis aggregata) is a typical example of such a flower, and hummingbirds are indeed among its most common visitors. But there is so much more to the story.

Scarlet gilia (also commonly known as skyrocket) is a wildflower in the phlox family (Polemoniaceae) that occurs in many parts of western North America. It is considered a biennial or short-lived perennial. It spends the first year or so of its life as a compact rosette of fern-like leaves. Later it sends up a branched, flowering stem that can reach 5 feet tall or more. The flowers are slender, trumpet-shaped, and composed of five fused petals that flare outward creating five prominent, pointed lobes. They are self-incompatible and require a pollinator in order to set seed. The stamens of an individual flower produce mature pollen before the stigma of that flower is ready to receive it – this is called protandry and is one mechanism of self-incompatibility.

The rosette of scarlet gilia (Ipomopsis aggregata)

The rosette of scarlet gilia (Ipomopsis aggregata)

The flowering period of scarlet gilia can last several months. Depending on the location, it can begin in mid-summer and continue through the fall. During this period, it produces dozens of flowers. It is also at this time that it runs the risk of being browsed by elk, mule deer, and other animals. This doesn’t necessarily set it back though, as it has the potential to respond by producing additional flowering stalks and more flowers. Its flowers are visited by a variety of pollinators including bumblebees, hawkmoths, butterflies, syrphid flies, solitary bees, and of course, hummingbirds. But hummingbirds, in many parts of scarlet gilia’s range are migratory, and that’s where things get interesting.

Early flowers of scarlet gilia are usually red. As the season progresses, flowers slowly shift from red to pink. In some cases, they lose all pigmentation and become white. In the early 1980’s, pollination biologists Ken Paige and Thomas Whitman set out to determine the reason for this shift in flower color. They spent three years observing a population of scarlet gilia on Fern Mountain near Flagstaff, Arizona. They noted that the change in flower color corresponded with the migration of hummingbirds and that the now lighter colored flowers continued to be pollinated by hawkmoths until the end of the flowering season.

ipomopsis aggregata

A series of experiments and observations led them to conclude that hummingbirds prefer darker colored flowers and hawkmoths prefer lighter colored flowers. By shifting to a lighter flower color, scarlet gilia appeared to be taking advantage of remaining pollinators after hummingbirds had migrated. They also concluded that the color change was not the cause of hummingbird migration since other flowers with nectar-rich, red, tubular flowers (specifically Penstemon barbatus) remained available in the area throughout their migration. It was also noted that the flowers of scarlet gilia shifted the timing of nectar production, presumably to better match the behavior of hawkmoths which are more active in the evenings.

No plants were observed shifting from light colored flowers to dark colored flowers, which further supported their conclusion. They also compared the population they studied to populations that do not lose their hummingbird pollinator and noted that when hummingbirds remain, the flowers of scarlet gilia don’t change color.

Scarlet gilia (Ipomopsis aggregata) with white flowers

Scarlet gilia (Ipomopsis aggregata) with white flowers

But just how effective are hummingbirds as pollinators of scarlet gilia? A seperate study carried out by a different group of researchers determined that, while hummingbirds were “the most common floral visitor,” long-tongued bumblebees were the more effective pollinator when it came to pollen deposition and seed set. The study involved observations of a scarlet gilia population in Colorado over a 5 year period. Considering how well the floral traits of scarlet gilia match up with the hummingbird pollination syndrome, it is surprising to learn that long-tongued bumblebees are comparatively more effective at pollinating them.

This study provides further evidence against strict adherence to pollination syndromes and the most effective pollinator principle, both of which imply specialized plant-pollinator interactions. (I wrote about these topics here, here, and here in earlier Year of Pollination posts.) In their discussion, the authors propose two possible explanations as to why scarlet gilia, despite its phenotypic floral traits, does not appear to be specialized. One explanation is that “natural selection favors a specialized [floral] morphology that excludes all but a single type of visitor, but there are constraints on achieving this outcome.” Perhaps the pollinators aren’t cooperating; their opportunism is leading them to “exploit flowers on which they can realize an energetic profit, even if they do not mechanically ‘fit’ very well.” The “sensory abilities” of the pollinators may be “broadly tuned,” making it difficult for plants to develop flowers with “private signals detectable only by specific types of pollinators.”

The second explanation proposed by the authors is that “selection favors some degree of floral generalization, but that flowers can retain features that adapt them to a particular type of pollinator in spite of generalization.” In the case of scarlet gilia, specialization could be detrimental because after they send up their flower stalks, they are doomed to die. This gives them only one season to set seed, and if hummingbirds are either not available that year or only available in limited numbers, a scarlet gilia population can lose the opportunity to reproduce. As the authors put it, “the fact that individual plants enjoy only a single season of reproduction, suggests the value of ‘backup’ pollinators.” This may also explain why flower color shifts in order to take full advantage of hawkmoth pollination after hummingbirds are gone.

Scarlet gilia is not only a beautiful and widespread wildflower, but also a plant with a very interesting story. Follow the links below to learn more about this fascinating plant: