Concluding the Summer of Weeds

“Most weeds suffer from a bad rap. Quite a few of the weeds in your garden are probably edible or even medicinal. Some invasive plants, including horsetail and nettle, are rich in minerals and can be harvested and used as fertilizer teas. Weeds with deep taproots, such as dandelions, cultivate the soil and pull minerals up to the surface. … Weeds are nature’s way to cover bare soil. After all, weeds prevent erosion by holding soil and minerals in place. Get to know the weeds in your area so you can put them to use for rather than against you.” — Gayla Trail, You Grow Girl

Great Piece of Turf by Albrecht Dürer (photo credit: wikimedia commons)

With summer drawing to a close, it is time to conclude the Summer of Weeds. That does not mean that my interest in weeds has waned, or that posts about weeds will cease. Quite the opposite, actually. I am just as fascinated, if not more so, with the topic of weeds as I was when this whole thing started. So, for better or worse, I will much have more to say on the subject.

In fact, I am writing a book. It is something I have been considering doing for a long time now. With so many of my thoughts focused on weeds lately, it is becoming easier to envision just what a book about weeds might look like. I want to tell the story of weeds from many different angles, highlighting both their positive and negative aspects. There is much we can learn from weeds, and not just how best to eliminate them. Regardless of how you feel about weeds, I hope that by learning their story we can all become better connected with the natural world, and perhaps more appreciative of things we casually dismiss as useless, less quick to jump to conclusions or render harsh judgments about things we don’t fully understand, and more inclined to investigate more deeply the stories about nature near and far.

Of course, I can’t do this all by myself. I will need your help. If you or someone you know works for or against weeds in any capacity, please put us in touch. I am interested in talking to weed scientists, invasive species biologists, agriculturists and horticulturists, edible weed enthusiasts, plant taxonomists, natural historians, urban ecologists, gardeners of all skill levels, and anyone else who has a strong opinion about or history of working with weeds. Please get in touch with me in one of several ways: contact page, Facebook, Twitter, Tumblr, or by commenting below.

Another way you can help is by answering the following poll. If there is more than one topic you feel particularly passionate about, feel free to answer the poll as many times as you would like; just wait 24 hours between each response. Thank you for your help! And I hope you have enjoyed the Summer of Weeds.

Quick Guide to the Summer of Weeds:

Advertisements

Rare and Endangered Plants: Texas Wild Rice

Some plants have native ranges that are so condensed that a single major disturbance has the potential to wipe them out of existence completely. They are significantly more vulnerable to change than neighboring plant species, and for this reason they often find themselves on endangered species lists. Zizania texana is one of those plants. Its range was never large to begin with, and due to increased human activity it now finds itself on the brink of extinction.

Zizania texana is one of three species of wild rice found in North America. The other two, Z. palustris and Z. aquatica, enjoy much broader ranges. Both of these species were once commonly harvested and eaten by humans. Today, Z. palustris is the most commercially available of the two. Commonly known as Texas wild rice, Z. texana, was not recognized as distinct from the other two Zizania species until 1932.

Herbarium voucher of Texas wild rice (Zizania texana) - photo credit: University of Texas Herbarium

Herbarium voucher of Texas wild rice (Zizania texana) – photo credit: University of Texas Herbarium

Texas wild rice is restricted to the headwaters of the San Marcos River in Central Texas. The river originates from a spring that rises from the Edwards Aquifer. It is a mere 75 miles long, but is home to copious amounts of wildlife, including several rare and endangered species. Before the 1960’s, Texas wild rice was an abundant species found along several miles of the San Marcos River. Its population and range has since been greatly reduced, and the native population is now limited to about 1200 square meters within the first two miles of the river.

Texas wild rice is an aquatic grass with long, broad leaves that remains submerged in the clear, flowing, spring-fed water of the river until it is ready to flower. Flower heads rise above the water, and each flower spike consists of either male or female flowers. The flowers are wind pollinated, but research has revealed that the pollen does not travel far and does not remain viable for very long. If a male flower is further than about 30 inches away from a female flower, the pollen generally fails to reach the stigma. The plants also reproduce asexually by tillering, but plants produced this way are genetically identical to the parent plant.

As people settled in the area around San Marcos Springs and began altering the river for their own use, Texas wild rice had to put up with a series of assaults and dramatic changes, including increased sediment and nutrient loads, variations in water depth and speed, trampling, and mechanical and chemical removal of the plant itself. Sexual reproduction became more difficult. In his book, Enduring Seeds, Gary Paul Nabhan describes one scenario: “streamflow had been increased to the extent that the seedheads, which were formerly raised a yard above the water, [were] now constantly being pummeled by the current so that they [remained] submerged, incapable of sexual reproduction.”

San Marcos, Texas – where the headwaters of the San Marcos River is located and where Texas wild rice has long called its home – is the location of Texas State University and is part of the Greater Austin metropolitan area. Thus, Zizania texana now finds itself confined to a highly urbanized location. The San Marcos Springs and River are regularly used for recreation, which leads to increased sediments, pollution, and trampling. Introduced plant species compete with Texas wild rice, and introduced waterfowl and aquatic rodents consume it. In this new reality, sexual reproduction will remain a major challenge, and a return to its original population size seems veritably impossible.

Texas wild rice (Zizania texana) and its urbanized habitat - photo credit: The Edwards Aquifer

Texas wild rice (Zizania texana) and its urbanized habitat – photo credit: The Edwards Aquifer

Attempts have and are being made to maintain the species in cultivation and to reintroduce it to its original locations, but its habitat has been so drastically altered that it will need constant management and attention for such efforts to be successful. As Nabham puts it, it is a species that has “little left of [its] former self in the wild – it is a surviving species in name more than in behavior…The wildness has been squeezed out of Texas rice.”

What if humans had stayed out of it? Would a plant with such a limited range and such difficulty reproducing sexually persist for any great length of time? It’s hard to say. If it disappears completely, what consequences will there be? It is known to provide habitat for the fountain darter, an endangered species of fish, as well as several other organisms; however, the full extent of its ecological role remains unclear. It will be nursed along by humans for the foreseeable future, but it may never regain its full glory. It is a species teetering on the edge of extinction, simultaneously threatened and cared for by humans – a story shared by so many other species around the world.

Additional Resources:

The Discovery of a Living Fossil

In the early 1940’s, the genus Metasequoia was only known scientifically in fossil form. It had, in its day, been a widespread genus, found commonly in many areas across the Northern Hemisphere. It thrived among the dinosaurs. However, sometime during the Pliocene, the genus was thought to have died out. Thousands of fossils were left behind, and that would have been the end of the story had a member of its genus not been discovered still alive in a Chinese province later that decade. Its discovery is easily one of the greatest botanical stories of the 20th century, fascinating in its own right. The circumstances surrounding its scientific description, as it turns out, are equally interesting.

In the January 2016 issue of Landscape Architecture Magazine, Kyna Rubin details the event in an article entitled The Metasequoia Mystery. It’s the type of story that you almost need a crazy wall to sort out. A broad cast of characters interacted at various levels in order to make this profound discovery during a tumultuous time when the world was at war and China was being invaded by Japan.

Speaking of Japan, let’s start there. In 1941, Japanese paleobotanist, Shigeru Miki, published research describing fossils that for decades were thought to be either Sequoia or Taxodium as a new genus, Metasequoia. As Rubin points out, due to the war, “not every Chinese botanist would have had access to recent international research, let alone articles by botanists of an enemy country.” This could explain why in 1943 when Zhan Wang – a professer of forestry at Beijing University and the forest administrator for the Ministry of Agriculture and Forestry – was introduced to a living Metasequoia by an old classmate and local villagers in the Hubei Province, he wasn’t sure what he was looking at.

The tree was obviously important to the local people. They called it shuisa (water fir) and had built a shrine around it. Wang collected several branches and some cones that had fallen on a rooftop. At the time he identified it as Glyptostrobus pensilis (water pine), a tree common to the area; but he may have wondered if this was correct.

Eventually Wang’s samples and the details of his collection were brought to the attention of Wanjun Zheng, a dendrologist at the National Central University. Intrigued, Zheng sent his graduate student, Jiru Xue, to collect more samples from the same tree that Wang had encountered. These samples were more complete, and when they were presented to Xiansu Hu – the director of Fan Memorial Institute of Biology in Beijing – the mystery was solved. Hu had access to Miki’s research and concluded that what they had was a living fossil.

In 1948, Hu and Zheng published a paper describing the species and giving it the official name, Metasequoia glyptostroboides. The discovery ignited the botanical community as well as the general public, and soon seeds of what became commonly known as dawn redwood were being disseminated across the globe. Unfortunately, Wang’s contribution was not mentioned in the original paper, and the exact account of the discovery became convoluted.

photo credit: wikimedia commons

Dawn redwood (Metasequoia glytostroboides) is a deciduous, medium to large tree. Its cones are round and about 1 inch long. Its leaves are oppositely arranged and have a feather-like appearance. Its bark is fibrous, stringy, and red-brown to gray in color.  (photo credit: wikimedia commons)

At some point, a discussion between Zheng and a forester named Duo Gan (also known as Toh Kan) revealed that Gan had come across the tree in 1941, but he did not make any collections. Despite Zheng learning of Gan’s encounter after Zheng and Hu’s original paper had been published, Gan’s story became prominent, further obscuring the role that Wang played.

It’s important to note that none of Wang’s original collections were used as the type specimen – the particular specimen of an organism to which the scientific name is formally attached and is referred to in the scientific literature. The type specimen was collected by Xue. This is not uncommon, as initial collections may not always be in the best condition and may not include all the parts and pieces necessary to identify and describe a new species. But, as Rubin notes, “it was Wang’s specimens [that Zheng and others] had first examined and those specimens brought the tree to their attention to begin with.” So Wang’s contribution is an important part of the story.

Thanks to Wang’s former students, his role in the discovery has received greater exposure. Jinshuang Ma in particular has made it his mission to highlight the part that Wang played in the event. Apart from maintaining a website all about Metasequoia, Ma also spent several years searching for a lost herbarium specimen collected by Wang, which he found in an abandoned herbarium in Nanjing. You can read about his find in this article from the August 2003 issue of the journal Taxon. (Ma’s well researched summary of the events surrounding the Metasequoia discovery is also worth reading.)

Failure to acknowledge Wang’s contribution (at least initially) perhaps didn’t make waves outside of China, but in Rubin’s words, “the omission of Wang’s contribution sparked immediate hullabaloo inside China’s botanical circles in the late 1940’s.” Power and class differences likely played a big role. Hu and Zheng were established scholars that had received their educations in the United States and France respectively. Wang was young, from a remote village, and had not studied abroad. While Wang “went on to become one of China’s most distinguished forestry experts and botanists,” he was early in his career at the time of the Metasequoia discovery.

A deep respect for the elders in his field may be the reason that Wang’s students claim that he “never complained” about his treatment. His students go on to say that Wang “was not interested in personal gain,” and instead was simply satisfied to see that Metasequoia “was now growing successfully all over the world and was better protected.” It is listed as endangered on the IUCN Red List and would likely be extinct in its shrunken native range had awareness of its existence not come about when it did.

Fossil of Metasequoia occidentalis - photo credit: wikimedia commons

Fossil of Metasequoia occidentalis – photo credit: wikimedia commons

There are plenty of other interesting details to this story. Read the full article and check out the links on metasequoia.org to learn more. The account of Jiru Xue (also known as Hsueh Chi-Ju), the graduate student who collected the type specimens, is particularly interesting. Suprisingly, the tree Wang and Xue took their collections from is still alive today and is estimated to be over 400 years old.

Other longform article reviews on Awkward Botany:

Year of Pollination: Mosquitoes as Pollinators

It is difficult to have positive feelings about mosquitoes, especially during summer months when they are out in droves and our exposed skin – soft, supple, and largely hair-free – is irresistible to them. We are viewed as walking blood meals by female mosquitoes who are simply trying to produce young – to perpetuate their species just like any other species endeavors to do. Unfortunately, we are left with small, annoying bumps in our skin – red, itchy, and painful – risking the possibility that the mosquitoes that just drew our blood may have passed along any number of mosquito-borne diseases, some (such as malaria) that potentially kill millions of people every year. For this, it is okay to hate mosquitoes and to long for the day of their complete eradication from the planet. However, their ecological roles (and yes, they do have some) are also worth considering.

There are more than 3,500 species of mosquito. Luckily, only 200 or so consume human blood. Mosquitoes go back at least 100 million years and have co-evolved with species of plants and animals found in diverse habitats around the world. Adult mosquitoes and their larvae (which live in standing water) provide food for a wide variety of creatures including birds, bats, insects, spiders, fish, frogs, lizards, and salamanders. Mosquito larvae also help break down organic matter in the bodies of water they inhabit. They even play an important role in the food webs found inside the pitchers of northern pitcher plants (Sarracenia spp.). Interestingly enough, Arctic mosquitoes influence the migration patterns of caribou. They emerge in swarms so big and so voracious that they have been said to kill caribou through either blood loss or asphyxiation.

However, blood is not the main food source of mosquitoes; flower nectar is. Males don’t consume blood at all, and females only consume it when they are producing eggs. Any insect that visits flowers for nectar has the potential to unwittingly collect pollen and transfer it to a nearby flower, thereby aiding in pollination. Mosquitoes are no exception. They have been observed acting as pollinators for a handful of species, and could be acting as pollinators for many more.

Bluntleaved orchid (Platanthera obtusata) is pollinated by mosquitoes. phot credit: wikimedia commons

Bluntleaved orchid (Platanthera obtusata) is pollinated by mosquitoes. photo credit: wikimedia commons

The scientific literature describes the pollination by mosquitoes of at least two plant species: Platanthera obtusata (syn. Habenaria obtusata) and Silene otites. P. obtusata – bluntleaved orchid – is found in cold, wet regions in North America and northern Eurasia. It is pollinated by mosquitoes from multiple genera including several species in the genus Aedes. Mosquitoes visit the flowers to feed on the nectar and, subsequently, pollinia (clusters of pollen) become attached to their eyes and are moved from flower to flower. This scenario likely plays out in other species of Arctic orchids as well*.

S. otites – Spanish catchfly – is a European species that is pollinated by mosquitoes and moths. Researches have been studying the floral odors of S. otites that attract mosquitoes, suggesting that determining the compounds involved in these odors “might lead to the development of new means of pest control and mosquito attractants and repellents.”

Northern House Mosquito (Culex pipiens) - one of the species of mosquitoes that has been observed pollinating Silene otitis. photo credit: www.eol.org

Northern House Mosquito (Culex pipiens) – one of the species of mosquitoes that has been observed pollinating Silene otites. photo credit: www.eol.org

Despite the list of functions that mosquitoes serve in their varied habitats, an article that appeared in Nature back in 2010 argues for wiping mosquitoes off the Earth, stating that “the ecological scar left by a missing mosquito would heal quickly as the niche was filled by other organisms.” And even though “thousands of plant species would lose a group of pollinators,” mosquitoes are not important pollinators of the “crops on which humans depend,” nor do they appear to be the sole pollinator of any single plant species [the species mentioned above are pollinated by other insects as well]. Eliminating mosquitoes, however, is more of a pipe dream than a realistic possibility as our “best efforts can’t seriously threaten an insect with few redeeming features.”

*Speaking of orchids and pollination, endless posts could be written about this incredibly fascinating and diverse group of plants and their equally fascinating and complex mechanisms surrounding pollination. There will be more to come on such topics. Meanwhile, it should be noted that orchids are also a notoriously threatened group of plants. To learn more about orchids and orchid conservation in North America, visit North American Orchid Conservation Center.

Read more about mosquito pollination here.

And now for your listening pleasure: