Drought Tolerant Plants: The Yarrows

Few plants are as ubiquitous and widespread as the common yarrow, Achillea millefolium. A suite of strategies have made this plant highly successful in a wide variety of habitats, and it is a paragon in terms of reproduction. Its unique look, simple beauty, and tolerance of tough spots have made it a staple in many gardens; however, its hardiness, profuseness, and bullish behavior have also earned it the title, “weed.” Excess water encourages this plant to spread, but in a dry garden it tends to stay put (or at least remain manageable), which is why it and several of its cousins are often included in or recommended for water efficient landscapes.

Achillea millefolium - common yarrow

Achillea millefolium – common yarrow

Common yarrow is in the aster family (Asteraceae) and is one of around 85 species in the genus Achillea. It is distributed throughout North America, Europe, and Asia. European plants have long been introduced to North America, and hybridization has occurred many times among the two genotypes.

Yarrow begins as a small rosette of very finely dissected leaves that are feathery or fern-like in appearance. These characteristic leaves explain its specific epithet, millefolium, and common names like thousand-leaf. Slightly hairy stems with alternately arranged leaves arise from the rosettes and are capped with a wide, flat-topped cluster of tightly-packed flowers. The flower stalks can be less than one foot to more than three feet tall. The flowers are tiny, numerous, and consist of both ray and disc florets. Flowers are usually white but sometimes pink.

The plants produce several hundred to several thousand seeds each. The seeds are enclosed in tiny achene-like fruits which are spread by wind and gravity. Yarrow also spreads and reproduces rhizomatously. Its roots are shallow but fibrous and abundant, and they easily spread horizontally through the soil. If moisture, sun, and space are available, yarrow will quickly expand its territory. Its extensive root system and highly divided leaves, which help reduce transpiration rates, are partly what gives yarrow the ability to tolerate dry conditions.

john eastman

Illustration of Achillea millifolium by Amelia Hansen from The Book of Field and Roadside by John Eastman, which has an excellent entry about yarrow.

Common yarrow has significant wildlife value. While its pungent leaves are generally avoided by most herbivorous insects, its flowers are rich in nectar and attract bees, butterflies, beetles, flies, and even mosquitoes. Various insects feed on the flowers, and other insects visit yarrow to feed on the insects that are feeding on the plant. Despite its bitterness, the foliage is browsed by a variety of birds, small mammals, and deer. Some birds use the foliage in constructing their nests. Humans have also used yarrow as a medicinal herb for thousands of years to treat a seemingly endless list of ailments.

Yarrow’s popularity as an ornamental plant has resulted in the development of numerous cultivars that have a variety of flower colors including shades of pink, red, purple, yellow, and gold. While Achillea millefolium may be the most widely available species in its genus, there are several other drought-tolerant yarrows that are also commercially available and worth considering for a dry garden.

Achillea filipendulina, fern-leaf yarrow, is native to central and southwest Asia. It forms large, dense clusters of yellow-gold flowers on stalks that reach four feet high. Its leaves are similar in appearance to A. millefolium. Various cultivars are available, most of which have flowers that are varying shades of yellow or gold.

Achillea alpina, Siberian yarrow, only gets about half as tall as A. filipendulina. It occurs in Siberia, parts of Russia, China, Japan, and several other Asian countries. It also occurs in Canada. Unlike most other species in the genus, its leaves have a glossy appearance and are thick and somewhat leathery. Its flowers are white to pale violet. A. alpina is synonymous with A. sibirica, and ‘Love Parade’ is a popular cultivar derived from the subspecies camschatica.

Achillea x lewisii ‘King Edward,’ a hybrid between A. tomentosa (woolly yarrow) and A. clavennae (silvery yarrow), stays below six inches tall and forms a dense mat of soft leaves that have a dull silver-gray-green appearance. Its compact clusters of flowers are pale yellow to cream colored. Cultivars of A. tomentosa are also available.

Achillea ptarmica, a European native with bright white flowers, and A. ageritafolia, a native of Greece and Bulgaria that is low growing with silvery foliage and abundant white flowers can also be found in the horticulture trade along with a handful of others. Whatever your preferences are, there is a yarrow out there for you. Invasiveness and potential for escape into natural areas should always be a concern when selecting plants for your garden, especially when considering a plant as robust and successful as yarrow. That in mind, yarrow should make a great addition to nearly any drought-tolerant, wildlife friendly garden.

More Drought Tolerant Plants Posts:

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.

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Lichen-eating Reindeer vs. Chernobyl Nuclear Disaster

Earlier this year I wrote about a lichen that was named after President Barack Obama in which I included a brief introduction to lichens. They are fascinating organisms that are actually two organisms in one – a fungus and an algae or cyanobacteria. They are not plants, but are often appreciated by plant enthusiasts, probably due to their plant-like appearances and behaviors and because they commonly associate with plants. Lichens have great ecological importance and are regularly used by a variety of animals for food and shelter. Their sensitivity to air pollution and acid rain is well documented, which brings me to a more tragic story about lichens.

As Heloise Rheault puts it in the book, Nature All Around Us, “Lichens live essentially from the light and water they obtain directly from their environment. Because they have no way to regulate or filter these resources, they directly absorb all particles suspended in the air and in rain, including all pollutants.” Absorbing enough pollutants over time can lead to the death of lichens, which is why researchers can use the presence or absence of lichens to map polluted areas. Lichens that have absorbed high levels of pollutants might also be eaten by animals, which moves these toxic substances up the food chain.

On April 26, 1986, the world’s worst nuclear disaster occurred at the Chernobyl Nuclear Power Plant in what at the time was the Ukrainian Soviet Socialist Republic. An explosion and fire completely destroyed one of the reactors and sent massive amounts of radioactive particles into the atmosphere. The radioactive fallout quickly spread across western USSR and Europe. Areas in close proximity obviously suffered the most dramatic effects of the explosion, but effects were also felt hundreds of miles away.

One distant area where effects were felt was Lapland, a region in northern Finland where the Sami people have lived for thousands of years. Lapland is about 2300 kilometers (1430 miles) north of Chernobyl, yet the fallout was detected shortly after the blast. Due to atmospheric nuclear weapons testing, regular monitoring of radiation levels in Lapland and the surrounding areas had been taking place long before the Chernobyl disaster. In Lapland, studies were focused on radiocesium concentrations in lichens and reindeer. Lichens are the main food source for reindeer during the winter when little else is available, and reindeer are regularly consumed by the Sami people. Threatened by fallout from Chernobyl, monitoring intensified in the area.

Reindeer in Lapland, Finland (photo credit: wikimedia commons)

Reindeer in Lapland, Finland (photo credit: wikimedia commons)

A report published in Rangifer in 1990 summarized results of sampling that was carried out in Lapland in 1986 – 1987. Hundreds of samples were taken from three species of lichens in the genus Cladonia (C. stellaris, C. mitis, and C. rangiferina). These species were selected because they are “the most important ground lichen species used as winter fodder by the reindeer.” Thousands of samples were also taken from the meat of slaughtered reindeer during this period. Researchers found that higher radiocesium concentrations in lichens within the sampling area correlated with higher radiocesium concentrations in reindeer within the same area. The test results were used to determine “whether the meat could be delivered for consumption or not.”

The researchers also found that contamination of the reindeer meat varied depending on when the reindeer were slaughtered. They determined that “lichens contain higher amounts of [radiation] activity than other forage,” so in the fall after the reindeer had spent the summer eating tree leaves and other plant material, “the activity concentration in the meat decreases rapidly.” Harvesting the reindeer from December through March, after they had spent the winter eating mostly lichens, resulted in meat with higher radiocesium concentrations.

Star reindeer lichen (Cladonia stallaris) - researchers found that the concentrations of radioactivity in this species of lichen was unevenly distributed in that "the top layer of the lichen was twice the concentration of the middle layer." (photo credit: www.eol.org)

Star reindeer lichen (Cladonia stellaris) – Researchers found that the concentration of radioactivity in this species of lichen was unevenly distributed, in that “the top layer of the lichen was twice the concentration of the middle layer.” (photo credit: www.eol.org)

An article published in the New York Times in September 1986 told a similar story. Laplanders in Sweden lamented that 97% of the first 1000 reindeer slaughtered so far that fall “measured in excess of permissible radiation levels and [were] declared unfit for human consumption.” The reindeer had spent the summer browsing “vegetation watered by the nuclear rains,” including “rain-sopped renlav lichen savored by the deer.” This was the first year of many in which contaminated meat would have to be disposed off. The article reports on the concerns of the Sami people that “their way of life is slipping into an irradiated limbo,” especially considering that the worst of the contamination has a half-life of 30 years and “the affected lichen will linger for a decade.” A paper published in the Journal of Environmental Radioactivity in 2005 reported that high levels of radioactivity were still being detected in this region’s “soil – plant/lichen – reindeer food chain” in the late 1990’s.

This is, of course, only one of many tragic and horrendous results of the Chernobyl disaster. Even now, 30 years after the event, effects are still being felt and clean up is ongoing.

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Thoughts on Equisetum Phylogenesis

This a guest post. Words and photos by Jeremiah Sandler.

These notes do not discuss either anatomy or medicinal uses of Equisetum. Both topics are worthy of their own discourse.

Plants in the genus Equisetum can be found on each continent of our planet, except for Antarctica. The plants are collectively referred to as scouring rush or horsetail.  Equisetum is in the division of plants called Pteridophytes, which contains all of the ferns and fern-allies (lycopods, whisk ferns, etc.) Pteridophytes are characterized by having a vascular system and by reproducing with spores, rather than seeds. Equisetum is the only living genus within the entire class Equisetopsida.  Within this single genus, there are a mere 20 species.

Picture 1

Equisetums can live pretty much anywhere. They can tolerate lots of shade, lots of sun, and virtually any soil condition (including submerged soil). Rhizomatous stems make it difficult for either disease or insects to kill an entire population. They do not require pollinators because they reproduce with spores.  Sounds like a recipe for reproductive and evolutionary success. Yet with all of these traits working in their favor, there is only a single genus left.  

Where’d they all go?

Picture 2

Let’s briefly consider the origin of these plants first. In the late Paleozoic Era, during the end of the Cambrian Period, these plants began their takeover. Shortly thereafter (about 70 million years later), in the Devonian Period, land plants began to develop a tree-like habit, also called “arborescence.” Tree-sized ferns and fern-allies ruled the planet. They formed the ancient forests.

The elements required for photosynthesis were plentiful. The planet was warm. Competition from the Cambrian Explosion of flora and fauna drove plants upwards towards the sky. Larger plants can both shade their competition and remain out of reach of herbivores. None of the Equisetum species alive today are near their ancestors’ height.  

picture 3

It is rather obvious why we don’t see as many Equisetum species, and why they are not as large: The planet now is not the same planet it once was. Oxygen levels back in those times were about 15% higher than today’s levels. Seed plants can diversify much faster than non-seed-bearing plants; Equisetum cannot compete with the rate of diversification of seed-bearing plants.

The most interesting predicament comes when Equisetum is compared with other Pteridophytes. Some ancient Pteridophytes still do have diversity of genera. True Ferns, as they’re called, are broad-leaved ferns. In the class Filicopsida, there are 4 orders of True Ferns containing about 100 genera combined. Equisetum has 1 order and 1 genera.

What’s the primary difference between these two classes of Pteridophytes?  Broad leaves.

Most pteridophytes tolerate some shade; most other plants can’t tolerate as deep of shade as ferns. More specifically, the amount of shade the plants create could be a deciding factor in this question. True ferns have all of the traits equisetums have, with one additional physical trait that has pulled them ahead: Broad leaves allow true ferns to actively shade out local competition while creating more habitat for themselves. Equisetums don’t have this aggressive capacity.

Of course there are other biological and evolutionary pressures affecting equisetums beside their lack of broad leaves. The structure they do possess has benefited them at a time when it was advantageous to have it.  Otherwise why would it exist? Equisetums remind me of the dynamic nature of a planet. I don’t anticipate equisetums coming back. 

Although, I find it entertaining to humor the idea that they might return to their former glory. The planet’s climate could change toward any direction (I’m not a climatologist, though). Maybe equisetums are adequately prepared to adapt to whatever changes come – or maybe we are observing the gradual decline of an old branch on the tree of life.  

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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.

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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

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.