cactus

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Randomly Selected Botanical Terms: Glochids

The spines of a cactus are an obvious threat. They are generally sharp, smooth, and stiff; as soon as you are stabbed by one, it is immediately clear that you’ve gotten too close. Sitting at the base of the spines – or in place of spines – on many species of cacti is a less obvious, but significantly more heinous threat. Unless you’re looking closely, this hazard is practically invisible, and the pain and irritation that can come as a result of close contact has the potential to last significantly longer than the sharp poke of a spine. This nefarious plant part is called a glochid, and if you’ve ever made contact with one (or more likely several dozen of them), it’s not something you will soon forget.

Opuntia polyacantha x utahensis

The spine of a cactus is actually a leaf. The area from which a spine emerges from the fleshy, photosynthetic stem of a cactus is called an areole, which is equivalent to a node or bud on a more typical stem or branch from which leaves emerge. In place of typical looking leaves, a cactus produces spines and glochids. Like spines, glochids are also modified leaves, although they appear more like soft, little tufts of hair. However, this unassuming little tuft is not to be trifled with.

Close inspection of a glochid (with the help of a microscope) reveals why you don’t want them anywhere near your skin. While the surface of a cactus spine is often smooth and free of barbs, glochids are covered in backwards-facing barbs. The miniscule size of glochids combined with their pliable nature and retrose barbs, make it easy for them to work their way into your skin and stay there. Unlike spines, glochids easily detach from a cactus stem. Barely brushing up against a glochid-bearing cactus can result in getting stuck with several of them.

Opuntia basilaris var. heilii

Because glochids can be so fine and difficult to see, you may not even be aware they are there. You probably won’t even feel them at first. Removing them is a challenge thanks to their barbs, and since you may not be able to remove them all, the glochids that remain in your skin can continue to cause irritation for days, weeks, or even months after contact. For this reason, cactuses are generally best seen and not touched, or at the very least, handled with extreme care.

Apart from being a good form of defense, the glochids of some cactus species can serve an additional function. Most cactus species occur in arid or semi-arid climates, where access to water can be quite limited. In order to increase their chances of getting the water they need, some desert plants are able to collect water from the air. A few species of cactus do this, and glochids are a critical component in making this happen.

Cylindropuntia whipplei

A study published in the Journal of King Saud University – Science (2020) examined the dew harvesting ability of Opuntia stricta, commonly known as erect prickly pear. As described above, the spines of O. stricta are smooth, while the glochids are covered in retrose barbs. Both structures are waterproof due to hardened cell walls and cuticles. However, due in part to the conical shapes of both the glochids and their barbs, water droplets from the air are able to collect on the tips of the glochids. From there, the researchers observed the droplets in their travel towards the base of the glochids. As they moved downward, small droplets combined to form larger droplets.

At the base of the glochids are a series of trichomes, which are small hair-like outgrowths of the epidermis. The trichomes do not repel water, but rather are able to absorb the droplets as they reach the base of the glochids. For a plant species that receives very little water from the soil, being able to harvest dew from the air is critical for its survival, and this is thanks in part to those otherwise obnoxious glochids.

See Also: Prickles

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Field Trip: Orton Botanical Garden

In the inaugural year of this blog, I wrote a short post about a visit to Plantasia Cactus Gardens, a botanical garden in Twin Falls, Idaho that specializes in cold hardy cactus and other succulents. I finally made a return visit all these years later (thanks to a co-worker who organized the trip). Back in 2013, the garden was private but open to the public by appointment. Today, the garden is still open by appointment but is now a 501(c)(3) non-profit organization with a new name: Orton Botanical Garden.

With the name change and non-profit status comes a new mission statement. The garden has been an impressive display of cold hardy cactus and succulents along with native and drought-tolerant plants for many years now. It has also long been a resource for educating visitors on the importance of these plants, as well as the importance of water conservation through water efficient landscaping. So the mission statement isn’t necessarily a new direction, but rather an affirmation of what this garden has done so well for years. Few gardens are doing cold hardy, drought-tolerant plants at the level that Orton Botanical Garden is.

Many of the plants at Orton Botanical Garden are made available to the public for purchase through an annual plant sale in May, as well as through an online store. This is another great service because sourcing some of these plants is not easy, and this one of the few places they can be found for sale.

Wherever you live in the world, this is a garden that should be on your bucket list. Even at a mere 5 acres in size, one could easily spend hours exploring it, and each visit reveals something new. What follows is just a small sampling of the things you will find there.

Toroweap hedgehog (Echinocereus coccineus var. toroweapensis)

scarlet hedgehog (Echinocereus coccineus var. coccineus)

White Sands kingcup cactus (Echinocereus triglochidiatus var. triglochidiatus)

Orcutt’s foxtail cactus (Escobaria orcuttii var. koenigii)

a peak down a shallow gully flanked by cholla (Cylindropuntia spp.)

Colorado hookless cactus (Sclerocactus glaucus)

Fremont’s mahonia (Mahonia fremontii)

close up of Fremont’s mahonia (Mahonia fremontii)

spiny pillow (Ptilotrichum spinosum)

hairstreak on cliff fendlerbush (Fendlera rupicola)

Utah sweetvetch (Hedysarum boreale)

Several species of buckwheats were in bloom, including this Railroad Canyon buckwheat (Eriogonum soliceps).

There were also quite a few penstemon species blooming, like this sidebells penstemon (Penstemon secundiflorus).

More Awkward Botany Field Trips:

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Botany in Popular Culture: The Tan Hua Flowers in Crazy Rich Asians

When a flower blooms, a celebration is in order. Flowers abound for much of the year, which means parties are called for pretty much non-stop (something Andrew W.K. would surely endorse). Since we can’t possibly celebrate every bloom, there are certain plants we have decided to pay more attention to – plants whose flowers aren’t so prolific, predictable, or long-lived; or plants whose flowers come infrequently or at odd times of the day (or night).

This is the case with the flowers of the night blooming cactus, Epiphyllum oxypetalum, which goes by many names including Dutchman’s pipe cactus, queen of the night, orchid cactus, night blooming cereus, and tan hua. Tan hua is the Chinese name for the plant, and this is how it is referred to in the book, Crazy Rich Asians by Kevin Kwan.

In the book, Nick Young brings his American girlfriend, Rachel Chu, to meet his ridiculously wealthy family in Singapore. Before the trip, Rachel was in the dark about the Young’s wealth. She first meets the family and their gargantuan mansion when Nick’s grandma, seeing that her tan hua flowers are about to bloom, throws an impromptu (and lavish) party. Nick refers to the flowers as “very rare,” blooming “extremely infrequently,” and “quite something to witness.”

In a seperate conversation, Nick’s cousin, Astrid, tries to convince her husband to attend the party by claiming, “it’s awfully good luck to see the flowers bloom.” Later, another one of Nick’s cousins tells Rachel, “it’s considered to be very auspicious to witness tan huas blooming.”

Tan hua (Epiphyllum oxypetalum) via wikimedia commons

Native to Mexico and Guatemala, E. oxypetalum was first brought to China in the 1600’s. Its beauty and intrigue along with its relative ease of cultivation helped it become popular and widespread across Asia and other parts of the world. Watching it bloom is considered a sacred experience by many, including in India, where it is said to bring luck and prosperity to households who are fortunate enough to see theirs bloom.

Epiphyllums are epiphytic, meaning they grow non-parasitically on the surfaces of other plants, such as in the crevices of bark or the crotches of branches. Like other cacti, they are essentially leafless, but their stems are broad, flat, and leaf-like in appearance. Showy, fragrant flowers are born along the margins of stems. The flowers of tan hua, as described in Crazy Rich Asians, appear as “pale reddish petals curled tightly like delicate fingers grasping a silken white peach.” A report (accompanied by photos) published by Sacred Heart University describes watching tan hua flowers progess from bud formation to full bloom, a process that took more than two weeks.

Tan huas are certainly not rare, as Nick described them. A number of Epiphyllum species and their hybrids are commonly cultivated; there is even an Epiphyllum Trail at San Diego Zoo’s Safari Park. Listed as “least concern” on the IUCN Red List, their popularity as ornamentals is noted but is not seen as affecting wild populations. Night blooming plants, while fascinating, aren’t all that rare either. Such plants have adapted relationships with creatures, like bats and moths, that are active during the night, employing their assistance with pollination. A paper published in Plant Systematics and Evolution describes the floral characteristics of Epiphyllum and similar genera: “The hawkmoth-flower syndrome, consisting of strongly-scented, night-blooming flowers with white or whitish perianths and long slender nectar-containing floral tubes is present in Cereus, Trichocereus, Selenicereus, Discocactus, Epiphyllum, and a number of other cactus genera.”

That being said, the specialness of a short-lived, infrequent, night blooming flower should not be understated, and really, parties being thrown in honor of any plant are something I can certainly get behind. Sitting in the courtyard late at night, the Young family and their guests watched as “the tightly rolled petals of the tan huas unfurled like a slow-motion movie to reveal a profusion of feathery white petals that kept expanding into an explosive sunburst pattern.” The look of it reminds Astrid of “a swan ruffling its wings, about to take flight.”

Later, “the tan huas began to wilt just as swiftly and mysteriously as they had bloomed, filling the night air with an intoxicating scent as they shriveled into spent lifeless petals.”

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Additional Resources:

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*Thank you Kathy for letting me borrow your Kindle so that I could write this post.

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How a Plant Could Just Kill a Man, part one

Plants have killed plenty of people. When plants are implicated in the death of a human, we typically think of plant poisonings. Rightly so since their are a slew of poisonous plants with the potential to kill. However, oftentimes plants kill (or seriously injure) people without employing toxic substances. One of the best examples of this is falling plant parts. Gravity couples with sheer coincidence and/or human error, and tragedy ensues. In an episode entitled Killer Plants of the now defunct podcast, Caustic Soda, the hosts present some of these distressing scenarios. What follows is a summary of the plants that made their list.

Branches falling from trees, whether dead or alive, can cause some serious damage. Trees in the genus Eucalyptus, commonly known as gum trees, are one group to be particularly wary of. There are more than 700 species of Eucalyptus, most of which occur in Australia. Not all are large trees, but those that are can be massive, reaching from 100 to 200 feet and taller. Eucalyptus trees regularly shed branches, often unexpectedly, leading to serious injury or death to anyone who may find themselves on the ground below. Shedding branches is likely a strategy for conserving water during hot, dry summers, and it is common enough that Australian parks departments issue safety advisories to avoid parking or camping below the trees. Even arborists don’t take their chances with these unpredictable trees.

Red River Gum Tree Eucalyptus camaldulensis - photo credit: wikimedia commons

River red gum (Eucalyptus camaldulensis) – photo credit: wikimedia commons

Of course, eucalyptus trees are not the only trees that drop their branches without warning. A falling branch in Yosemite National Park claimed two victims last summer, for example; and falling branches have claimed the lives of a great deal of forest workers, wildland firefighters, and other forest visitors. This happens frequently enough that the branches in question have been given the ominous name widowmakers, and the U.S. Department of Labor lists them as one of many “potential hazards” in the logging industry. What are the chances of being killed by a falling tree? The Ranger’s Blog set out to answer that question and, to set your mind at ease, determined that the chances are pretty slim.

What about other falling plants? Saguaro cactus, for example. Carnegiea gigantea is a tree-like, columnar cactus native to the Sonoran Desert. It is a very slow growing and long-lived species that generally reaches around 40 feet tall but can potentially grow much taller. Saguaros are considered tree-like for their tall stature and branching habit, although not all saguaros develop branches. Some saguaro branches (or “arms”) can be quite large and considerably heavy. In 1982, an Arizona man discovered this when he and a friend were out shooting saguaros. Stupidly, the man repeatedly shot at the arm of an enormous cactus. Ultimately the arm split off and landed on the man, crushing him to death. Of course, saguaros don’t have to be shot at to fall on you. Another Arizona man was fixing a water leak in a Yuma subdivision when a sixteen foot tall saguaro toppled over on him. The man was crushed but lived to tell about it.

Saguaro cactus (Carnegiea gigantea) - photo credit: wikimedia commons

Saguaro cactus (Carnegiea gigantea) – photo credit: wikimedia commons

Palm trees drop things on people, too. One tragic example involves a man in Los Angeles standing below a Canary Island date palm (Phoenix canariensis) waiting for a ride to a funeral. The 2000 pound crown of the palm tree split and fell, pinning the man to the ground. Bystanders were unable to remove the crown, and the man died.

The coconut palm (Cocos nucifera) has an additional deadly weapon – its fruit. While the number of deaths by coconut are often exaggerated, they do occasionally occur. Injuries by coconut are more frequent, so precaution around the trees should be taken. After all, coconut palms can reach heights of 80 feet or more, and mature coconuts can weigh more than three pounds (considerably more when they are wet). A falling coconut is something to be mindful of, an observation that led Dr. Peter Barss to study coconut related injuries in Papa New Guinea over a period of 4 years. His research was published in 1984 in the Journal of Trauma and was later taken out of context and used to make the claim that coconuts kill significantly more people per year than sharks. Publicity spawned by this urban myth helped Barss earn an Ig Noble Prize in 2001. Concerns about coconut related injuries also led officials in India to order the removal of coconut palms around the Gandhi Museum in preparations for President Barack Obama’s 2010 visit.

Back in Australia, the towering bunya pine (Araucaria bidwillii) has its equivalent to the coconut in its massive cone. Measuring around a foot long and weighing in at 20+ pounds, these cones make living near bunya pines an act that is “not for the faint hearted.” When the cones are falling, they warrant warnings from the Australian government to keep away from these 90 foot tall trees. This harrowing feature puts bunya pines on a list of infamous plants in Australia with the potential to kill.

Bunya pine cone (Araucaria bidwillii) - photo credit: www.eol.org

Seed cone of bunya pine (Araucaria bidwillii) – photo credit: www.eol.org

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Year of Pollination: Stamen Movement in the Flowers of Prickly Pears

Last week I made an effort to convince you to add a prickly pear or two to your water-wise gardens. One standout reason to do this is their strikingly beautiful flowers. Apart from being lovely to look at, many prickly pear flowers have a distinct feature that makes them quite fascinating. A demonstration of this feature can be seen in the following video.

 

Stamen movement in response to touch is a characteristic of many species in the genus Opuntia. It isn’t exclusive to Opuntia, however, and can also be seen in Berberis vulgaris, Portulaca grandiflora, Talinum patens, among others. Knowing this makes me want to touch the stamens of any flower I can find just to see what will happen.

The response of stamens to touch has been known for at least a few centuries, but recent research is helping us gain a better understanding of how and why this phenomenon occurs. In general, this movement is thought to assist in the process of cross-pollination. In some cases it may also aid in self-pollination. Additionally, it can have the effect of protecting pollen and nectar from “robbers” (insects that visit flowers to consume these resources but that do not provide a pollination service). Quite a bit of research has been done on this topic, so to simplify things I will be focusing on a paper published in a 2013 issue of the journal, Flora.

In their paper entitled, Intriguing thigmonastic (sensitive) stamens in the plains prickly pear, Cota-Sanchez, et al. studied the flowers of numerous Opuntia polyacantha individuals found in three populations south of Saskatoon, Saskatchewan, Canada. Their objective was to “build basic knowledge about this rather unique staminal movement in plants and its putative role in pollination.” They did this by conducting two separate studies. The first involved observing flower phenology and flower visitors and determining whether the staminal movement is a nasty (movement in a set direction independent of the external stimulus) or a tropism (movement in the direction of the external stimulus). The second involved using high-powered microscopes to analyze the morphology of the stamens to determine any anatomical traits involved in this movement. While the results of the second study are interesting, for the purposes of this post I have chosen to focus only on the findings of the first study.

An important note about the flowers of O. polyacantha is that they are generally protandrous, meaning that the anthers of a single flower release pollen before the stigmas of that same flower are receptive. This encourages cross-pollination. An individual flower is only in bloom for about 12 hours (sometimes as long as 30 hours), however flowering doesn’t occur all at once. The plants in this study flowered for several weeks (from the second week of June to the middle of July).

To determine whether the staminal movement is a nasty or a tropism, the researchers observed insects visiting the flowers. They also manually stimulated the stamens with various objects including small twigs, pencils, and fingers, touching either the inner sides of the filaments (facing the style) or the outer sides (facing the petals). In every observation, the stamens moved in the same direction, “inwards and towards the central part of the flower.” This “consistent unidirectional movement, independent of the area stimulated” led the researchers to categorize the staminal movement of O. polyacantha as thigmonastic. They also observed that staminal movement slowed as the blooming period of an individual flower was coming to an end – “and finally when all the anthers had dehisced, the anthers rested in a clustered position, marking the end of anthesis.” Furthermore, it was observed that “filaments move relatively faster in sunny, warm conditions as opposed to cloudy, cold and rainy days.”

The researchers went on to discuss unique features of the stamens of O. polyacantha. Specifically, the lower anthers contain significantly more pollen than the upper anthers. When the stamens are stimulated, their movement towards the center of the flower results in the lower anthers becoming hidden below the upper anthers. They also noted that small insects less than 5 millimeters in size did not trigger stamen movement. Further observations of the insect vistors helped explain these phenomena.

SAMSUNG

A “broad diversity of insects” was observed visiting the flowers, from a variety of bees (bumblebees, honeybees, sweat bees, and mining bees) to bee flies, beetles, and ants. The large bees  were determined to be the effective pollinators of this species of prickly pear. Their large weight and size allows them to push down through the upper anthers to the more pollen-abundant anthers below. After feeding on pollen and nectar, they climb out from the stamens and up to the stigma where they take off, leaving the flower and depositing pollen as they go. Because the bees are visiting numerous flowers in a single flight and the flowers they visit are protandrous, pollen can be transferred from one flower to another and self-pollination can be avoided.

Beetles were observed to be the most common visitors to the flowers; however, they were not seen making contact with the stigma and instead simply fed on pollen and left. Ants also commonly visit the flowers but largely remain outside of the petals, feeding from “extranuptial nectaries.” In short, beetles and ants are not recognized as reliable pollinators of this plant.

Similar results involving two other Opuntia species were found by Clemens Schlindwein and Dieter Wittmann. You can read about their study here.

There are lots of flower anatomy terms in this post. Refresh your memory by visiting another Awkward Botany post: 14 Botanical Terms for Flower Anatomy.

Recently I received a note from a reader requesting that I include a link to subscribe to this blog’s RSS Feed. I have now made that available, and it can be found at the top of the sidebar.

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Drought Tolerant Plants: Prickly Pears

In the introduction to this series about drought tolerant plants, I defended water efficient gardens by claiming they don’t have to be the “cacti-centric” gardens that many visualize upon hearing terms like “xeriscape,” “water-wise,” and “drought tolerant.” And this is absolutely true. However, that won’t stop me from suggesting that such landscapes include a cactus or two. Despite their menacing and potentially dangerous spines, they are actually quite beautiful, and a cactus in bloom is really a sight to behold. Together with a variety of grasses, herbaceous flowering plants, and shrubs, cactus can add unique forms, textures, and focal points that will enhance the look and function of a water-wise garden. This is why I recommend considering cactus, particularly (as far as this post is concerned) one of the many varieties of prickly pears.

The cactus family (Cactaceae) has a native range that is limited to the Americas. Within that range it is expansive, and cactus species can be found in diverse regions from Canada down to Patagonia. The genus Opuntia (the prickly pears) is the most widespread of any genus in the cactus family consisting of at least 300 species found throughout the Americas. Even a brief investigation into Opuntia will reveal that there is considerable controversy as to how many species there actually are and what to call them. This is partly due to the large ranges that species in this genus can have and the diverse habitats they can be found in within those ranges, resulting in a single species having many forms, varieties, and/or subspecies. Hybridization is also common in this genus where ranges overlap, augmenting the challenge of identification.

Generally, prickly pears have flattened stems with spines and glochids emerging from small bumps called areoles. Their flowers are large, showy and a shade of either yellow, orange, or pink and sometimes white. They form fruits that are either fleshy and juicy with a red or purple hue or hard, dry and a shade of brown or tan. The flattened stems are called pads or cladodes and can be quite large in some species, while diminutive and sometimes rounded in others. Some species are without spines, but all have glochids – tiny, barbed, hair-like structures found in clusters on the stems and fruits. While the spines can be painful when they penetrate skin, the glochids are far more irritating as they easily detach themselves from the plant and work their way into the skin of their victims. The fleshy fruits, called tunas, can be eaten after first taking care to remove the glochid-infested outer layer. The young stems of many species can also be eaten – they are referred to as nopales and are common in Mexican cuisine.

Flowers of Opuntia sp. with bee inside flower on the left

Flowers of Opuntia sp. with bee inside flower on the left

Again speaking generally, prickly pears are very easy to propagate and cultivate. Their two main preferences are full sun and well-drained soil. If you are worried that the soil you are planting them in is going to stay too wet for too long, amend it with some gravel. This is especially important if you live in a climate that receives lots of precipitation or that has cold, wet winters. Once established, prickly pears will move around the garden. If that becomes a problem, expanding plants are easily pruned and traveling plants are easily removed.

I live in a climate that requires the selection of cold hardy prickly pears, so I am taking my specific recommendations from two books: Cacti and Succulents for Cold Climates by Leo J. Chance and Hardy Succulents by Gwen Moore Kelaidis. If you live in a warmer climate, your options will be greater. Still, the options for cold regions are pretty numerous, so for the sake of space I am narrowing my list down to a handful that stand out to me at this particular moment.

Three eastern United States species of prickly pears (O. compressa, O. macrorhiza, and O. humifusa) are, according to Chance, “more capable of dealing with wet and cold conditions than almost any other members of the cactus family.” They still require well-drained soil though. An appealing trait is their large, juicy, red fruits that can add garden interest in late summer and fall. Opuntia engelmannii is another species with the potential to tolerate cold, wet conditions. Its size is appealing to me, with pads that reach a foot wide and plants that grow several feet tall. Chance advises finding “a clone that is known to be cold tolerant” and making some space for it, “as it becomes huge in time.” The most cold tolerant prickly pear may be Opuntia fragilis. It is a diminutive plant with a large native range and a variety of forms, some with rounded pads “shaped like marbles.”

Fruits ("tunas") of Opuntia engelmannii - photo credit: www.eol.org

Fruits (“tunas”) of Opuntia engelmannii – photo credit: www.eol.org

Opuntia fragilis 'Frankfurt' - photo credit: wikimedia commons

Opuntia fragilis ‘Frankfurt’ – photo credit: wikimedia commons

Opuntia polyacantha is a prickly pear native to my home state, Idaho. It is found at high elevations throughout the Intermountain West and is also found on the Great Plains. It has many forms and varieties, and its flowers are various shades of pink or yellow. It is a fast growing species and spreads around easily. Other cold hardy species include Opuntia macrocentra (which has a very attractive yellow flower with a red-orange center), Opuntia erinacea (commonly known as hedgehog prickly pear for its abundant, long spines that can obscure the pads), and Opuntia microdisca (a tiny Argentinian prickly pear with pads that barely reach an inch across but, as Chance says, “works very well in a dry rock garden with other miniatures”).

Pads of Opuntia polyacantha

Pads and spines of Opuntia polyacantha

A post about Opuntia could go on indefinitely due to the sheer number of species and their diverse forms and attributes. This is meant merely to pique your interest. The flowers, if nothing else, should certainly interest you. In her book, Kelaidis calls them “improbably beautiful,” and goes on to say that they are “often papery, always glistening and showy.” Chance likens them to “any fancy rose” because they are “extraordinarily large, brightly colored, [and] eye catching.” Next week, as part of Awkward Botany’s Year of Pollination, I will present another reason to be fascinated with the flowers of Opuntia. For now, I will leave you to ponder this word, “thigmonasty.”

Want to learn more about prickly pears? Check out Opuntia Web.

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Year of Pollination: An Argentinian Cactus and Its Unlikely Pollinator

A few weeks ago I wrote about pollination syndromes – sets of floral triats that are said to attract specific groups of pollinators. In that post I discussed how pollination syndromes have largely fallen out of favor as a reliable method of predicting the pollinators that will visit particular flowers. In this post I review a recent study involving a species of cactus in Argentina that, as the authors state in their abstract, “adds another example to the growing body of mismatches between floral syndrome and observed pollinator.”

Denmoza rhodacantha is one of many species of cacti found in Argentina. It is the only species in its genus, and it is widely distributed across the east slopes and foothills of the Andes. It is a slow growing cactus, maintaining a globulous (globe-shaped) form through its juvenile phase and developing a columnar form as it reaches maturity. D. rhodacantha can reach up to 4 meters tall and can live beyond 100 years of age. Individual plants can begin flowering in their juvenile stage. Flowers are red, nectar rich, scentless, and tubular. The stigma is lobed and is surrounded by a dense grouping of stamens. Both male and female reproductive organs are extended above the corolla. The flowers have been described by multiple sources as being hummingbird pollinated, not based on direct observation of hummingbirds visiting the flowers, but rather due to the floral traits of the species.

Denmoza rhodacantha illustration - image credit: www.eol.org

Denmoza rhodacantha illustration  (image credit: www.eol.org)

In a paper entitled, Flowering phenology and observations on the pollination biology of South American cacti – Denmoza rhodacantha, which was published in volume 20 of Haseltonia (the yearbook of the Cactus and Succulent Society of America), Urs Eggli and Mario Giorgetta discuss their findings after making detailed observations of a population of D. rhodacantha in early 2013 and late 2013 – early 2014. The population consisted of about 30 individuals (both juveniles and adults) located in the Calchaqui Valley near the village of Angastaco, Argentina. At least three other species with “hummingbird-syndrome flowers” were noted in the area, and three species of hummingbirds were observed during the study periods. Over 100 observation hours were logged, and during that time “the studied plants, their flowering phenology, and flower and fruit visitors were documented by means of photographs and video.”

The flowers of D. rhodacantha only persist for a few short days, and in that time their sexual organs are only receptive for about 24 hours. The flowers are self-sterile and so require a pollinator to cross pollinate them. Despite their red, tubular shape and abundant nectar, no hummingbirds were observed visiting the flowers. One individual hummingbird approached but quickly turned away. Hummingbirds were, however, observed visiting the flowers of an associated species, Tecoma fulva ssp. garrocha. Instead, a species of halictid bee (possibly in the genus Dialictus) was regularly observed visiting the flowers of D. rhodacantha. The bees collected pollen on their hind legs and abdomen and were seen crawling across the lobes of the stigma. None of them were found feeding on the nectar. In one observation, a flower was visited by a bee that was “already heavily loaded with the typical violet-coloured pollen of Denmoza,” suggesting that this particular bee species was seeking out these flowers for their pollen. Small, unidentified beetles and ants were seen entering the flowers to consume nectar, however they didn’t appear to be capable of offering a pollination service.

D. rhodacantha populations have been observed in many cases to produce few fruits, suggesting that pollination success is minimal. The authors witnessed “very low fruit set” in the population that they were studying, which was “in marked contrast to the almost 100% fruit set rates of the sympatric cactus species at the study site.” This observation wasn’t of great concern to the authors though, because juvenile plants are present in observed populations, so recruitment appears to be occurring. In this study, dehisced fruits were “rapidly visited by several unidentified species of ants of different sizes.” The “scant pulp” was harvested by smaller ants, and larger ants carried away the seeds after “cleaning them from adhering pulp.”

The authors propose at least two reasons why hummingbirds avoid the flowers of D. rhodacantha. The first being that the native hummingbirds have bills that are too short to reach the nectar inside the long tubular flowers, and often the flowers barely extend beyond the spines of the cactus which may deter the hummingbirds from approaching. The second reason is that other plants in the area flower during the same period and have nectar that is easier to gather. The authors acknowledge that this is just speculation, but it could help explain why the flowers are pollinated instead by an insect (the opportunist, generalist halictid bee species) for whom the flowers “could be considered to be ill adapted.” The authors go on to say, “it should be kept in mind, however, that adaptions do not have to be perfect, as long as they work sufficiently well.”

Patagona gigas (giant hummingbird) was observed approaching the flower of a Denmoza rhodacantha but quickly turned away (photo credit: www.eol.org)

Patagona gigas (giant hummingbird) was observed approaching the flower of a Denmoza rhodacantha but quickly turned away (photo credit: www.eol.org)

More Year of Pollination posts on Awkward Botany:

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Field Trip: Lady Bird Johnson Wildflower Center, part two

This is the second in a series of two posts about my recent trip to Lady Bird Johnson Wildflower Center in Austin, Texas. You can read the first post here. Both posts are comprised of mostly pictures, as they tell a much better story about the place then my words can. However, even pictures don’t do the place justice; it’s definitely a site that you are going to have to see for yourself. I highly recommend it.

One name that kept coming up during the native plant conference was Doug Tallamy – and for good reason. Tallamy has long promoted and encouraged the use of native plants in landscapes, largely for the creation of wildlife habitat in urban and suburban areas. In 2007 he put out a book entitled, Bringing Nature Home: How You Can Sustain Wildlife with Native Plants, in which he made a strong argument for native plant gardens. His book and lectures have inspired many to seek out native plants to include in their yards. What was lacking in his book, however, was detailed information on the horticulture and design aspects of using native plants. So in 2014, together with Rick Darke, Tallamy put out The Living Landscape, an impressive tome outlining how to create beautiful and functional gardens using native plants. Both books are well worth your time.

The plant name following each photo or series of photos links to a corresponding entry in the Native Plant Database which is managed by the Wildflower Center’s Native Plant Information Network. The quotes that accompany the plant names are taken from the Native Plant Database entries.

Ilex vomitoria (yaupon). “The leaves and twigs contain caffeine, and American Indians used them to prepare a tea which they drank in large quantities ceremonially and then vomited back up, lending the plant its species name, vomitoria. The vomiting was self-induced or because of other ingredients added; it doesn’t actually cause vomiting.”

aesculus pava var pava 3

Aesculus pavia var. pavia (red buckeye). “Long popular for its brilliant, hummingbird-attracting spring flowers and rich green foliage, it is found in nature most often as a plant of woodland edges, where it can get morning sun and afternoon shade.”

tillandsia recurvata 5

Tillandsia recurvata (ball moss). An epiphyte commonly found on trees within its range, including Quercus fusiformis (escarpment live oak) a dominant tree at the Wildflower Center. “Some have been introduced into other warm regions and cultivated for use as ornamentals or for their edible fruit.”

Opuntia ellisiana (spineless prickly pear). A spineless form of Opuntia cacanapa derived from cultivation. “The spineless prickly pear is a great addition to the landscape for those seeking a cactus form, showy blooms, and bright red cactus fruits (tunas). Beware, although it doesn’t have long sharp spines, the tiny glochids (slivers) are very irritating to the skin if the plant is not handled correctly.”

Gelsemium sempervirens (Carolina jessamine). “The flowers, leaves, and roots are poisonous and may be lethal to humans and livestock. The species nectar may also be toxic to honeybees if too much is consumed, and honey made from Carolina jessamine nectar may be toxic to humans.”

Lonicera sempervirens (coral honeysuckle). “Flowers attract hummingbirds, bees, and butterflies. Fruits attract quail, purple finch, goldfinch, hermit thrush, and American robin.”

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Succulent Blogs on Tumblr

About four months ago, Awkward Botany branched out into the world of Tumblr, a short-form blogging platform with a heavy social media bent. I haven’t put as much time into it as I would like (and I still have lots to learn about it), but so far the time I have spent there has been entertaining and informative.

One discovery I have made is that there are lots of tumblogs dedicated to botany and horticulture. This shouldn’t come as a surprise though; there are tumblogs concerning pretty much any topic you can think of. Plus, people love plants, so why shouldn’t there be tumblogs aplenty devoted to them?

One subsection of plant-related tumblogs that I have particularly enjoyed following are the cactus and succulent themed ones. In the botanical world, which is replete with diversity, there is no shortage in the variety of colors, textures, and forms to be found. Cacti and succulents are especially fascinating in this regard. Now thanks to Tumblr, hours can be spent admiring them while sitting comfortably in front of a computer screen. I say that with a hint of sarcasm, of course. Seeing these plants in person (either in their natural habitat or in cultivation) would obviously be better, but when that option is not available, the internet is the next best thing.

Over the past few months I have collected a list of cactus and succulent related tumblogs. Below are my favorites. Some of them consist exclusively of photos grabbed from other sites, while others are composed of personal photos along with a mix of other photos. A few of them also offer advice and take questions concerning cactus and succulent cultivation.

what a nice little succulent

What A Nice Little Succulent – a blog about growing succulents in a Brooklyn apartment…from seed! What’s not to like? Great blog name, too.

jacculents

Jack + Succulents – Jack grows succulents in Malaysia and shares advice on how to cultivate and care for them. He also likes coming up with clever names, like Jacculents and Jacktus.

cactguy

Cactguy – Speaking of clever names, Cactguy is a blog produced by a self-proclaimed “cactus fiend.” His pictures are labeled so that you can not only admire the plants but learn the names of them as well.

cactiheart

Not Cact-I, Cact-Us – Yes, the clever names abound in the cactus and succulent loving community.

succulent lover

Succulent Lover – A love for succulents pure and simple.

These five blogs barely scratch the surface. There are lots more great ones out there, including Succulents Forever!, Sweet Succulents, and Succulent Love. An excellent one if you are looking for more information about succulents is Cactus Man Dan, which is written by an obsessed cactus and succulent collector in England. He can help you answer any questions you may have about growing and identification.

Do you know of any other cactus and succulent (or plants in general) tumblogs that you would like to recommend? If so, leave your recommendations in the comment section below. And if you feel so inclined, please follow Awkward Botany on Tumblr and/or Twitter. Lastly, with this post I am introducing the new Reviews and Recommendations tab. Go there to read my past review and recommendation posts, and stay tuned for many more to come. 

 

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Plantasia Cactus Gardens

If you ever find yourself in southern Idaho, there is a secret garden that I highly recommend checking out. I say “secret” because it is a private garden, but if you make an appointment ahead of time, the owners will gladly let you see it. It’s called Plantasia Cactus Gardens, and it is 5 acres filled with a very impressive collection of cacti and other desert plants. Most of the plants are native to the western United States, but there are a few plants from other parts of the world as well. The gardens are beautifully designed and very well-kept. The owners are very friendly and incredibly knowledgable and could probably spend hours with you talking about each plant in their collection. Along with maintaining the garden, the owners also propagate cacti and other drought tolerant plants and sell them during an annual plant sale and through mail order. Check out their website (which is updated regularly) for more information.

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