The Serotinous Cones of Lodgepole Pine

Behind the scales of a pine cone lie the seeds that promise future generations of pine trees. Even though the seeds are not housed within fruits as they are in angiosperms (i.e. flowering plants), the tough scales of pine cones help protect the developing seeds and keep them secure until the time comes for dispersal. In some species, scales open on their own as the cone matures, at which point winged seeds fall from the tree, taking flight towards their new homes. In other species, the scales must be pried open by an animal in order to free the seed. A third group of species have what are called serotinous cones, the scales of which are sealed shut with resin. High temperatures are required to soften the resin and expose the seeds.

Serotinous cones are a common trait of pine species located in regions where wildfire naturally and regularly occurs. One such species is lodgepole pine (Pinus contorta), which is found in abundance in forests across much of western North America. Lodgepole pine is a thin-barked tree species that burns easily and is often one of the first plants to recolonize after a stand-replacing wildfire. There are 3 or 4 subspecies of lodgepole pine. The one with the largest distribution and the one that most commonly exhibits serotinous cones is P. contorta subsp. latifolia, which occurs throughout the Rocky Mountains, north into the Yukon, and just west of the Cascade Range.

needles of lodgpole pine (Pinus contorta)

Lodgepole pine grows tall and straight, generally maxing out at around 80 feet tall. Its needles are about two and a half inches long, are borne in bundles of two, and tend to twist away from each other, which is one explanation for the specific epithet, contorta. Its cones are egg-shaped with asymmetrical bases, measuring less than two inches long with prickly tips at the ends of each scale. The seeds of lodgepole pine are tiny with little, papery wings that aid in dispersal. The cones can remain attached to the tree for 15-20 years (sometimes much longer), and the seeds remain viable for decades. In non-serotinous cones, the scales start opening on their own in early autumn. Serotinous cones require temperatures of 45-50°C (113-122°F), to release the resin bond between the scales. Some cones that happen to fall from the tree can open when exposed to particularly warm temperatures on the ground. Otherwise, it takes fire to free the seeds.

Serotinous cones aren’t a guarantee, and the percentage of trees with serotinous cones compared to those with non-serotinous cones varies widely across the range of lodgepole pine, both in space and in time. One reason for this is that trees with serotinous cones don’t develop them until they reach a certain age, generally around 20-30 years old, or perhaps as old as 50 or 60. The cones of young trees are all non-serotinous. But some trees never develop serotinous cones at all. Serotiny is a genetic trait, and there are various factors that either select for or against it. A number of factors are at play simultaneously over the life of a tree and across a population of trees, so it is difficult to determine exactly why the percentage of serotinous cones is so variable across the range of the species. What follows are a few potential explanations for this phenomenon.

closed cone of lodgepole pine (Pinus contorta)

As a fire-adapted, pioneer species, lodgepole pine has evolved to live in environments where fire is predictably common. Serotinous cones help ensure that a population won’t be wiped out when a massive wildfire comes through. After the fire has passed and the seeds are released, lodgepole pine can quickly repopulate the barren ground. As long as fire occurs within the lifespan of a population of similarly aged trees, it is advantageous for the majority of individuals to maintain their serotinous trait. If the population is located in an area that historically does not see much fire, serotinous cones may be a disadvantage and can have adverse effects on the longevity of that population.

A study published in Ecology in 2003 looked at the influence that the frequency of fire has on lodgepole pine stands found at low and high elevations in Yellowstone National Park. At lower elevations, where summer temperatures are warmer and precipitation is relatively minimal, fires occur more frequently compared to higher elevations, which tend to be cooler and wetter. The researchers found that at lower elevations when fires occurred at short intervals (less than 100 years between each fire), lodgepole pine was slower to repopulate compared to longer intervals. This suggests that the percentage of serotiny found in stands that experienced short fire intervals was low, and that stands with long fire intervals exhibit a higher percentage of serotiny. After all, as mentioned above, lodgepole pines don’t start developing serotinous cones until later in life.

At higher elevations, where fire occurs less frequently, lodgepole pines were found to have a low percentage of serotinous cones regardless of the age of the stand. Because the trees at high elevations are more likely to die of old age rather than fire, maintaining serotinous cones would be a disadvantage. Open cones are preferred. Thus, at least in this study, a greater percentage of serotinous cones was found in lodgepole pines at lower elevations compared to those at higher elevations. Latitude, elevation, mountain pine beetle attacks, and other environmental factors have all been used to explain differences in serotiny. However, the factor that seems to have the greatest influence is the frequency of fire. As James Lotan writes in a 1976 report: “A high degree of cone serotiny would be expected where repeated, high-intensity fires occur. Where forest canopies are disrupted by factors other than fire, open cones annually supply [seed] for restocking disturbances such as windfalls.”

That being said, one other factor does appear to play a critical role in whether or not lodgepole pines produce serotinous cones, and that is seed predation by squirrels. In a paper published in Ecology in 2004, researchers wondered why the percentage of serotinous cones wasn’t even higher in populations where fire reliably occurred during the lifetime of the stand. To help answer this question they looked at the activities of pine squirrels, which are the main seed predator of lodgepole pine seeds. Pine squirrels visit the canopy of lodgepole pines and consume the seeds found in serotinous cones. Because non-serotinous cones quickly shed their seeds, serotinous cones are a more reliable and accessible food source, and because pine squirrels are so effective at harvesting the seeds of serotinous cones, the researchers concluded that, “in the presence of pine squirrels, the frequency of serotiny is lower and more variable, presumably reflecting,” among a variety of other factors, “the strength of selection exerted by pine squirrels.”

A study published in PNAS in 2014 added evidence to this conclusion. While acknowledging that fire plays a major role in the frequency of serotinous cones, the researchers asserted that “squirrels select against serotiny and that the strength of selection increases with increasing squirrel density.” However, despite making it easier for squirrels to access their seeds, lodgepole pines maintain a degree of serotinous cones, since clearly their main advantage is retaining a canopy-level seed bank from which seeds are released after a fire and by which a new generation of lodgepole pines is born.

open cones of lodgepole pine (Pinus contorta)

Further Reading and Viewing:

Meet Erigeron linearis

Erigeron is a genus of herbaceous, flowering plants consisting of between 390 and 460 species and is a member of the aster/sunflower family (Asteraceae). Plants in this genus are annuals, biennials, or perennials and are mainly found in temperate regions around the world. At least 163 species occur in the contiguous United States. Erigeron diversity is particularly high in western states; however, each state is home to at least one Erigeron species.

A common name for plants in this genus is fleabane. This name comes from an outdated belief that the plants can be used to repel or poison fleas, flies, gnats, and other tiny insects, a belief for which there is no evidence. In Ancient Greek, the name Erigeron is said to mean something akin to “old man in the early morning,” likely referring to the appearance of the seed heads which look like little tufts of white hair. Some Erigeron species are also commonly referred to as daisies.

desert yellow fleabane (Erigeron linearis)

One species of Erigeron that I would like you to meet is Erigeron linearis. While most of the plants in this genus have flowers that are white, pink, or various shades of purple, E. linearis is a yellow-flowered species, hence the common name, desert yellow fleabane. Another common name for this plant is narrow leaved fleabane, a reference to its linear leaves. E. linearis is a small plant with a prominent taproot that reaches up to 20 centimeters tall and forms a leafy, rounded mat or cushion of whitish or gray-green, alternately arranged leaves. The white appearance is due to numerous, fine, appressed hairs on the leaves and stems. Flower stalks are produced in abundance in late spring through early summer and are mostly leafless. They reach above the mound of leaves and are each topped with at least one flower head, which nods at first, but then straightens out as the flowers open. Each flower head is about 2 centimeters wide and is typical of plants in the sunflower family, with a cluster of deep yellow disc florets in the center, surrounded by ray florets that are lighter in color. Both disc and ray florets are fertile; however, the disc florets have both “male” (stamens) and “female” (pistils) flower parts, while the ray florets have only “female” parts. The involucre, which sits at the base of the flowers, is egg-shaped or hemispheric and made up of a series of tiny, fuzzy bracts called phyllaries.

the flower head of desert yellow fleabane (Erigeron linearis)

The fruit of Erigeron linearis is called a cypsela, an achene-like fruit that is characteristic of plants in the sunflower family. The fruits are miniscule and topped with a pappus composed of short outer bristles and longer, pale, inner bristles. The two types of pappus bristles (or double pappus) must be the reason for the scientific name this species was originally given in 1834, Diplopappus linearis. While the seeds of more than 80% of flowering plant species found in dryland regions exhibit some form of dormancy, a study published in Plant Biology (2019), found that E. linearis is one of the few species with non-dormant seeds. This means that for those of us interested in growing plants native to the Intermountain West, E. linearis is a pretty easy one to grow and is a great addition to water-wise gardens, pollinator gardens, and rock gardens.

Erigeron linearis seedling

Erigeron linearis is distributed across several western states and into Canada. It is found in northern California, eastern Oregon and Washington, southern British Columbia, across Idaho and east into southern Montana, western Wyoming and northwestern Utah. It is found at low to moderate elevations in open, rocky foothills, grasslands, sagebrush steppe, and juniper woodlands. It prefers well-drained soils and full sun. It is one of many interesting plants found on lithosols (also known as orthents), which are shallow, poorly develop soils consisting of partially weathered rock fragments. In the book Sagebrush Country, Ronald Taylor calls lithosols “the rock gardens of the sagebrush steppe,” and refers to E. linearis and other members of its genus as “some of the more colorful components of the lithosol gardens.” E. linearis is a food source for pronghorn, mule deer, and greater sage-grouse, and the flowers are visited by several species of bees and butterflies. The plant is also a larval host for sagebrush checkerspots.

desert yellow fleabane (Erigeron linearis)

Additional Resources:

Weeds of Boise: iNaturalist Observations

So far, the lists of weeds at each of the Weeds of Boise sites look pretty similar, with several weed species showing up at nearly every site and other species only occasionally making an appearance. This isn’t a surprise really. The flora of any region typically has several species that are dominant, along with species that occur less frequently. Wild urban flora – or in other words, the naturalized weeds in urban areas – may follow a similar pattern. My unscientific and infrequent surveys, all of which have been pretty close to where I live, aren’t yet representative of the Boise area as a whole. However, something like iNaturalist might help with that. For this reason, I took a look at iNaturalist observations to get a better idea as to which species dominate the wild urban flora of Boise, Idaho.

iNaturalist is a website and app that allows users to identify, map, and share observations of living things with the rest of the world. It has been in use for over a decade and is easily one of the most popular community science, biodiversity mapping, and identification apps around. Even though it is not the primary mission of iNaturalist, the information gathered from user observations is frequently used in scientific research and conservation efforts. With over 80 million observations worldwide, iNaturalist offers a pretty decent picture of the plants, animals, fungi, and other living things found in just about any given location. You don’t even need to a registered user to browse the observations and find out what has been spotted near you or across the globe.

In order to come up with a list of weeds that have been observed in Boise by iNaturalist users, I entered “Boise City Metropolitan Area, ID, USA” into the Location field. It is possible to narrow your search to individual neighborhoods or even broaden your search to include a larger area. Clicking on the map allows you to see the area represented in your search. For my purposes, I figured that the number of observations would change if the area covered was either smaller or larger, but the list of weed species would largely remain the same. After you select your search area, you can filter out the results. Clicking on the plant icon limits the search to plants. At first I selected only introduced plants, but that seemed to eliminate a few of the plants that I would consider weeds, so instead I scanned through the entire list of plants and made a list of each of the weed species and how many times each had been observed.

There are of course limitations to using iNaturalist to create species lists, the main one being that you are relying on decisions made by iNaturalist users when it comes to what gets reported. In my case, in which I’m looking for a list of weed species found in Boise, I know there are plenty of weeds that iNaturalist users either aren’t noticing or aren’t bothering to report. The reported observations are also not likely to match the frequency at which they occur in the environment. Still, it’s interesting to see what gets reported and how often. It’s also interesting to see reports of things that I haven’t seen before. By clicking on individual observations, you can see where those observations were made, which means I know where I can go to find species I haven’t yet encountered.

What follows is a list of the top 25 weeds in the Boise area based on the number of iNaturalist observations, along with photos of some of the most reported weeds. A few of the species on the list, like cornflower, straddle the line between weed and desirable plant. I included them anyway because they are known to be naturalized outside of garden borders, even though some of the reported observations may have been intentionally planted within garden borders.

bittersweet nightshade (Solanum dulcamara)
pink-flowered field bindweed (Convolvulus arvensis)
great mullein (Verbascum thapsus)

Top 25 Weeds in the Boise City Metropolitan Area According to iNaturalist Observations (as of September 21, 2021)

  1. great mullein (Verbascum thapsus) – 110 
  2. common dandelion (Taraxacum officinale) – 98
  3. redstem stork’s-bill (Erodium cicutarium) – 83
  4. chicory (Cichorium intybus) – 62
  5. heart-podded hoary cress (Lepidium draba) – 61
  6. cornflower (Centaurea cyanus) – 58
  7. rush skeletonweed (Chondrilla juncea) – 56
  8. purple loosestrife (Lythrum salicaria) – 49
  9. bittersweet nightshade (Solanum dulcamara) – 47
  10. alfalfa (Medicago sativa) – 46
  11. common soapwort (Saponaria officinalis) – 43
  12. dwarf mallow (Malva neglecta) – 42
  13. donkey tail (Euphorbia myrsinites) – 40 
  14. poison hemlock (Conium maculatum) – 39
  15. field bindweed (Convolvulus arvensis) – 39 
  16. bulbous meadow-grass (Poa bulbosa) – 39
  17. yellow salsify (Tragopogon dubius) – 38
  18. crested wheatgrass (Agropyron cristatum) – 37 
  19. cheatgrass (Bromus tectorum) – 36
  20. moth mullein (Verbascum blattaria) – 36 
  21. hound’s-tongue (Cynoglossum officinale) – 31
  22. Virginia creeper (Parthenocissus quinquefolia) – 30
  23. catnip (Nepeta cataria) – 29
  24. white clover (Trifolium repens) – 29
  25. yellow iris (Iris pseudacorus) – 28
Virginia creeper (Parthenocissus quinquefolia)
catnip (Nepeta cataria)
common soapwort (Saponaria officinalis)

Awkward Botanical Sketches #5: Leaves of Yellowstone Edition

Earlier this month, I met up with Eric LoPresti and others at Yellowstone National Park to help take a census of Abronia ammophila, a rare plant endemic to the park and commonly referred to as Yellowstone sand verbena. Abronia (a.k.a. the sand-verbenas) is a small genus of plants in the family Nyctaginaceae that is native to western North America. Several species in the genus have fairly limited distributions, and as the common name implies, members of this genus generally occur in sandy soils. A. ammophila is no exception. A report written by Jennifer Whipple and published in 2002 described it as “restricted to stabilized sandy sites that lie primarily just above the maximum splash zone along the shoreline of [Yellowstone Lake].” Despite the large size of the lake, A. ammophila is not widespread. Most individuals are found along the north shore of the lake, and even there it has been declining. According to Whipple’s report, “Yellowstone sand verbena has been extirpated from a significant portion of its original range along the shoreline of the lake due largely to human influences.”

Like other sand verbenas, A. ammophila has sticky leaves to which sand particles easily adhere, a phenomenon known as psammophory and an act that may help in defense against herbivory. The plant grows prostrate across the sand and produces attractive, small, white, trumpet-shaped flowers in groups of up to 20 that open wide when light levels are low, such as in the evening and in times of heavy cloud cover. The flowers are self-fertile, but insects may also play a role in pollination. It is imperative that questions surrounding its pollination biology, seed dispersal, and other factors regarding its life history are answered in order to halt any further decline of the species and ensure its survival for generations to come.

While in Yellowstone, I enjoyed looking at the all plants, several of which were new to me. I decided to sketch a few of the leaves that I found common around our campsite. I was particularly interested in discolored, diseased, drought-stressed, and chewed-on leaves, since they are more interesting to sketch and color. While I was at it, I attempted to draw a Yellowstone sand verbena seedling as well.

wild strawberry (Fragaria sp.)
Richardson’s geranium (Geranium richardsonii)
lodgepole pine (Pinus contorta)
veiny dock (Rumex venosus)
cinquefoil (Potentilla sp.)
seedling of Yellowstone sand verbena (Abronia ammophila)

More Awkward Botanical Sketches

Book Review: In Defense of Plants

Many of us who are plant obsessed didn’t connect with plants right away. It took time. There was a journey we had to go on that would ultimately bring us to the point where plants are now the main thing we think about. After all, plants aren’t the easiest things to relate to. Not immediately anyway. Some of us have to work up to it. Once there, it’s pretty much impossible to go back to our former lives. What was once just a background of green hues is now a rich cast of characters, each with their own name, unique features, and distinct story to tell. Essentially, we went through what Matt Candeias refers to as our ” green revolution.” Candeias – author and host of the long-running blog and podcast, In Defense of Plants – shares his story of learning to love plants and offers a convincing arguement for why you should love them too in his new book, aptly titled, In Defense of Plants.

It’s hard to picture Candeias as anything but a plant lover. If you’ve been following his work, you’ll know he makes it a point to put plants at center stage. It seems that much of the popular content available about plants focuses on the usefulness of plants as they pertain to humans. In many cases it can be easier to find out how to grow a certain plant species than to learn about where it’s from and what it’s like in the wild. Candeias let’s the plants speak for themselves by giving them a voice through his blog, podcast, and now his book. Through the stories he shares we get a peek into the way Candeias sees plants, with the hope being that others might also “be bitten by the botanical bug.”

One of the first plants that captured the attention of Candeias was perennial blue lupine (Lupinus perennis). While assisting with a habitat restoration project at a sand and gravel quarry, Candeias was tasked with improving the establishment of lupine, which is the host plant for the caterpillars of an endangered species of butterfly called Karner blue. The work he did at the quarry and the botanical research that went into it helped Candeias realize that plant’s aren’t at all boring, but are “incredibly interesting organisms worthy of respect and admiration” and that “plants can be both surprisingly relatable and incredibly alien all at once.” His “green revolution” had begun.

The seeds of lupine are dispersed ballistically. As the seed pods dry, tension builds. Then, as Matt Candeias writes in In Defense of Plants, “with an audible pop, the pods eventually explode, catapulting the seeds out into the environment.”

In each chapter of In Defense of Plants we get a peak into the experiences that brought Candeias to where he is now as he discovers the wonder of plants. His personal stories help introduce the main topic of each chapter. Topics include plant sex, plant dispersal, plant defenses, carnivorous plants, and parasitic plants. From countless possible examples, Candeias selects a few of his favorite plant species to help illustrate each topic. Along the way, the reader is presented with various other interesting plant-related facts as Candeias discusses the behaviors of some of the world’s most fascinating plants. In the chapter on dispersal, for example, unlikely agents of seed dispersal (like catfish!) are introduced, as well as phenomena like geocarpy, in which plants are essentially planting themselves.

Carnivorous plants provide an excellent gateway into convincing people who claim to have no interest plants that they actually do. It’s difficult to deny the impressive nature of a meat-eating plant. In the carnivorous plant chapter, Candeias introduces us to the various ways such plants capture and consume their prey, and even wonders if some of these plants should be considered omnivores. After all, certain butterworts digest pollen that falls onto their sticky leaves, and some bladderworts suck in plenty of algae and possibly gain nutrients from the act. If capturing insects inside leaves modified to look like pitchers or on leaves covered in digestive enzyme-producing glands doesn’t impress you, consider the carnivorous actions of corkscrew plants, which drill their leaves into the soil to go after soil-dwelling organisms like protozoans and worms.

Parasitic plants should also excite a reluctant plant lover. These are plants that take all or most of what they need to survive from another plant or host organism. Mistletoes are one of the more familiar parasitic plants, and Candeias describes several, including one that lives almost entirely within the stems of cacti. In fact, “you would never know a cactus had been infected until the mistletoe living within decides to flower,” at which point the flowers push their way out through the sides of the cactus. Dodder is another fairly common, highly specialized, and easy to identify parasitic plant. It basically looks like “a tangled pile of orange spaghetti tossed over the surrounding vegetation.” Orchids, a favorite of Candeias, are known for being mycoheterotrophs, which essentially means they parasitize fungi. Their seeds come unequipped with the energy stores needed to get going, so they borrow resources from mycorrhizal fungi in order to get their start. Years pass before the orchid can offer anything in return.

Datura is a genus of plants that produces toxic compounds like scopolamine and atropine. In his book, In Defense of Plants, Matt Candeias warns, “it would only take a small amount of these chemicals to completely ruin your week and slightly more to put you in a grave.”

After spending more than 200 pages celebrating plants and their amazing abilities and diversity, it’s fitting that Candeias spends the final chapter of his book mourning some of the ways the actions of humans threaten the existence of so many plants. He remarks how unfortunate it is that “plants with their unseeing, unhearing, unfeeling ways of life usually occupy the lowest rung of importance in our society.” Many of us barely notice the loss, yet “plants are the foundation of functioning ecosystems.” Due to that fact, “destroying plant communities causes disastrous ripples that reverberate throughout the entire biosphere of our planet.” Everything suffers when plants are lost. Fortunately, the book doesn’t end on this dark note. Candeias’s overall message is hopeful. When we learn to understand, appreciate, and care about plants, we will want to do everything we can to protect and restore them. With any luck, after reading this book, you too will want to offer your time, energy, and resources in defense of plants.

Listen to Matt talk about his new book on this episode of his podcast.

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Tea Time: Linden Flower Tea

Lindens make great trees for urban areas. A few species and hybrids in particular are commonly planted in parks, yards, and along the streets of cities across the northern hemisphere and have been for decades – centuries even. They cast dense shade, are tolerant of a variety of climates and soil conditions, and are generally easy to maintain. For much of the year as you move throughout the city you live in, you likely pass by dozens of lindens without thinking twice about them. They are ubiquitous, conventional, ordinary, common. Unless they’re in bloom. For a few weeks in early to mid-summer, flowering lindens produce an impossibly sweet fragrance that can’t be ignored. Along with the scent comes the sound of hundreds of buzzing bees collecting pollen and nectar from the pendulous blooms.

Lindens are trees and shrubs in the family Malvaceae and genus Tilia. Around 30 or so species are found in temperate regions across the northern hemisphere, mostly in Europe and Asia. Depending on who you ask, there are between one and three species native to North America. Tilia caroliniana and Tilia heterophylla are considered by some to be varieties of Tilia americana, or American basswood, which is distributed across central and eastern United States and north into parts of Canada. Another common name for linden is lime because words used to refer to the tree in older languages were similar to the word lime. The name basswood comes from the tree’s fibrous inner bark, known as bast.

Linden leaves are generally heart-shaped and asymmetrical with serrate margins. Small clusters of little yellow to white flowers form at the end of a slender stem attached to a narrow, ribbon-like, yellow-green bract. The bract aids in seed dispersal by helping the fruits float on the wind away from the parent tree in a manner similar to the samaras of maple trees. The fruits are small, round, hardened drupes that resemble little peas. The fragrant, nectar-rich flowers are not only favored by beekeepers for honey production, but also have a long history of being harvested for making tea (i.e. tisane). Linden flower tea is said to have a number of medicinal uses and health benefits, all of which I take with a grain of salt. This series of posts isn’t meant to be an investigation into the health claims of plants, but instead an opportunity for me – out of sheer curiosity – to try making tea out of a variety of different plants . If medicinal uses interest you, I encourage you to seek out credible, peer-reviewed sources.

I made linden flower tea from flowers I collected from Tilia cordata, commonly known as littleleaf linden. It was an easy one to find due to its popularity as an urban tree. The natural distribution of littleleaf linden extends from Britain across Europe and into western Asia. Its triangular-ovate shaped leaves are 4-10 centimeters long, glossy green on top, and pale green on the bottom with tufts of orange hairs along the leaf veins, concentrated at the base of the leaf where the leaf blade meets the petiole. The tree can reach up to 21 meters tall and has an oval or rounded-pyramidal shape, though many trees in urban areas are cultivars and can be smaller and more compact.

I harvested the flowers – bracts and all – in late June. It’s advised that they not be harvested directly after a rain (or after being hit by sprinklers), and that they are harvested when the flowers are newly opened. I presume this is because the flowers are at their freshest at this point and will be the best for making tea. I layed the flowers out to dry on a clean kitchen towel on top of a metal cake rack. It only takes 2 or 3 days for them to dry. After drying I removed and saved all the flowers and threw out the bracts and stems, but apparently you can use the entire inflorescence if you’d like.

There are several linden flower tea recipes online. I went with 3 cups of boiling water poured over 1 tablespoon dried linden flowers, covered and steeped for 15 minutes. The resulting tea was an appealing pastel yellow color. I tried it plain as well as sweetened with a little bit of honey. I preferred it sweetened, but unsweetened wasn’t too bad, just a little bitter. It has a floral taste and pleasant smell. Sierra said it tasted earthy, like something she wasn’t supposed to be drinking. Despite that odd review, she said she liked it. Since several sources discussed the calming, sleep-inducing effects of the tea, I made sure to drink it in the evening when it would be normal for me to be feeling sleepy. I suggest you do the same.

More Tea Time Posts on Awkward Botany

Drought Tolerant Plants: Blue Flax

“Lewis’s prairie flax is a pretty garden ornamental suited to hot, dry sites. Each morning delicate sky blue flowers open on slender arching stems, only to fall off in the afternoon and be replaced by others the next morning. In spite of its fragile appearance, it is quite sturdy and may put out a second flush of blossoms on new growth in late summer.”Common to the This Country: Botanical Discoveries of Lewis and Clark by Susan H. Munger


When selecting plants for a waterwise garden, it is imperative that at least a portion of the plants are easy to grow and maintain and are adapted to a wide variety of conditions. This will ensure a more successful garden, both functionally and aesthetically. Luckily, there are a number of drought-tolerant plants that pretty much anyone can grow without too much trouble. Blue flax, in my opinion, is one such plant.

You may be familiar with flax as a culinary plant, known for its edible seeds which are used to make flour (i.e. meal) and oil. Or perhaps you’ve used linseed oil, a product of flax seeds, to protect wooden, outdoor furniture or in other wood finishing projects. You may also think of linen when you think of flax; and you should, because linen is a textile made from the fibrous stems of the flax plant. All of these products generally come from a domesticated, annual flax known as Linum usitatissimum – a species that has been of benefit to humans for millenia. Various species of flax have also been planted for erosion control, fire breaks, forage for livestock, and in pollinator-friendly gardens. Flax seeds, a common ingredient in bird seed mixes, provide food for birds and other small animals. All this to say, humans and flax share a long history together, and it deserves a place in your garden.

The flax species profiled here is actually two species: Linum lewisii and Linum perenne. That’s because these two species look nearly identical and are both used as garden ornamentals and in wildflower seed mixes. They are also both known as blue flax, among myriad other common names. Due to their similiarity, L. lewisii is considered by some to be a subspecies of L. perenne.

Linum lewisii is found across western North America and received its name after being collected by a member of the Lewis and Clark Expedition. The plant collection was brought back from the expedition and determined to be new to western science. It was described and named by Frederick Pursh. Linum perenne is a European species which was introduced to North America as an ornamental and has since become widely naturalized. In 1980, a naturalized selection of L. perenne was released for use in restoration plantings under the cultivar name ‘Appar’ with the understanding that it was L. lewisii. A genetic study later revealed that the cultivar was instead L. perenne. The study also provided evidence that “North American Lewis flax and European perennial blue flax are reproductively isolated,” suggesting that they are indeed two separate species.

Despite being separate species, telling them apart can be a challenge. Blue flax plants grow from a taproot and woody base and are multistemmed, reaching two to three feet tall. The stems are thin yet stringy, wiry, and not easily torn, which helps explain why flax is such a good plant for making textiles. Short, slender leaves are alternately arranged along the length of the stems, while flower buds form at the ends of stems in loose clusters. Flowers bloom early in the day and are spent by the afternoon. They are 5-petaled, saucer-shaped, and a shade of blue – from whitish blue to deep blue – depending on the plant. Small, round, 10-chambered seed capsules form in the place of flowers, each chamber housing one or two flat, shiny, dark brown seeds. Flowers bloom daily in succession up towards the ends of stems even as the fruits of spent flowers lower on the stalk mature.

seed capsules of blue flax

A close look at their flower parts is really the only way you might be able to tell these two species apart. Blue flax flowers have five stamens topped with white anthers and five styles topped with little, yellow stigmas. The flowers of L. lewisii are homostlyous, which means their styles are all the same length and are generally taller than or about the same height as the stamens. The flowers of L. perenne are heterostylous, which means their flowers can either have styles that are much longer than their stamens or stamens that are much longer than their styles. Each plant in a population of L. perenne has either all long-styled flowers or all short-styled flowers. In a mixed population of L. perenne and L. lewisii, separating the long-styled L. perenne plants from the L. lewisii plants presents a challenge (at least for me).

long-styled blue flax flower
short-styled blue flax flower

Due to the similarity of these two species, it’s easy to see how the plants or seeds of blue flax could easily be mislabeled and sold as one species even though they are the other species. This could be a problem in a restoration planting where seed source and identity is critical, but in your garden, it’s really no big deal. Both species are great for waterwise and pollinator gardens. They are equally beautiful and easy to grow and care for. If nothing else, perhaps the challenge in identifying them will encourage you to take a closer look at your flowers and familiarize yourself with their tinier parts – an act all of us amateur botanists could stand to do more often.

The photos in this post were taken at Idaho Botanical Garden in Boise, Idaho.

More Drought Tolerant Plants Posts:

Weeds of Boise: Railroad Tracks Between Kootenai Street and Overland Road

Walking along railroad tracks is a pretty cool feeling. It’s also a good place to look for weeds. Active railroad tracks are managed for optimum visibility and fire prevention, which means that trees and shrubs near the tracks are removed creating plenty of open space on either side. Open areas in full sun are ideal places for a wide variety of weed species to grow. Trains passing through can also be sources or dispersal agents of seeds, so there’s a chance that you may see things growing alongside railroad tracks that you don’t often see elsewhere. All this means that railroad tracks in urban areas are great locations to familiarize yourself with your city’s wild urban flora.

I visited a small section of railroad tracks between Kootenai Street and Overland Road in Boise. At one point, this was a pretty active railroad. Passenger trains once moved along these tracks, and the Boise Depot, which is less than a mile from this location, was one of several stops between Portland, OR and Salt Lake City, UT. Unfortunately, those services ended in 1997 and have yet to resume, despite continued support for bringing passenger rail back to the region. Still, freight trains pass by with some frequency.

Managing weeds along railroad tracks in urban areas can be tricky. There is little else in the way of vegetation to compete with the weeds. The tracks are also adjacent to parks, homes, schools, gardens, and other locations that make herbicide applications complicated. The species of weeds can also vary widely from one mile to the next, so management decisions must also vary. It’s especially important that the ballast directly beneath and on either side of the tracks is kept weed free in order to prevent fires and improve visibility. All of this and more makes weed control along railroad tracks one of the most challenging jobs around. Luckily, for someone that likes to look at weeds, it means there will always be interesting things to see near the tracks, including for example this colony of harvester ants that I came across while identifying weeds. I was happy to see that they were collecting the samaras of Siberian elm (Ulmus pumila), one of several weedy trees in the Treasure Valley.

What follows are a few images of some of the weeds I encountered along the railroad tracks between Kootenai Street and Overland Road, as well as a list of the weeds I was able to identify. The list will grow as I identify the mystery weeds and encounter others that I missed, as is the case with all posts in the Weeds of Boise series.

Virginia creeper (Parthenocissus quinquefolia)
blue mustard (Chorispora tenella)
cleavers (Galium aparine)
whitetop (Lepidium sp.)
Himalayan blackberry (Rubus bifrons)
bush honeysuckle (Lonicera sp.)
Siberian elm (Ulmus pumila)
English ivy (Hedera helix)
kochia seedlings (Bassia scoparia)
  • Arctium minus (common burdock)
  • Bassia scoparia (kochia)
  • Bromus diandrus (ripgut brome)
  • Bromus tectorum (cheatgrass)
  • Chorispora tenella (blue mustard)
  • Conium maculatum (poison hemlock)
  • Convolvulus arvensis (field bindweed)
  • Cirsium arvense (creeping thistle)
  • Dactylis glomerata (orchardgrass)
  • Descurainia sophia (flixweed)
  • Elaeagnus angustifolia (Russian olive)
  • Epilobium ciliatum (northern willowherb)
  • Equisetum sp. (horsetail)
  • Erodium cicutarium (redstem filaree)
  • Galium aparine (cleavers)
  • Hedera helix (English ivy)
  • Hordeum murinum (wild barley)
  • Lactuca serriola (prickly lettuce)
  • Lepidium sp. (whitetop)
  • Lonicera sp. (bush honeysuckle)
  • Parthenocissus quinquefolia (Virginia creeper)
  • Poa bulbosa (bulbous bluegrass)
  • Poa pratensis (Kentucky bluegrass)
  • Rubus bifrons (Himalayan blackberry)
  • Rumex crispus (curly dock)
  • Secale cereale (feral rye)
  • Taraxacum officinale (dandelion)
  • Ulmus pumila (Siberian elm)

Do you live near railroad tracks? What weeds are growing there, and do you feel as cool as I do when you walk the tracks?

Eating Weeds: Japanese Knotweed

When I first learned that Japanese knotweed was edible, I had my doubts. Sure, lots of plants may be edible, but are they really something you’d want to eat? I know Japanese knotweed as one of the most notorious weeds on the planet. Its destructive, relentless, and prolific nature has landed it on the world’s 100 worst invasive species list, right up there with black rats, Dutch elm disease, and killer algae. Having encountered a fair number of Japanese knotweed stands, the first thing to come to mind has never been, “that looks delicious.” Mature stalks stand as tall as 3 meters with broad, leathery leaves and hollow, bamboo-like stems. Their late summer flowers – a mess of tiny white florets on sprawling flower stalks – are a pollinator’s delight and favored by beekeepers for their abundant nectar. I don’t doubt that the honey produced from such an encounter is tasty, but the plant itself? I needed convincing.

Finally, I looked into it. I came across recipes of Japanese knotweed pickles and learned that it was the young, early emerging shoots that were sought after. That changed my perspective. Certainly you wouldn’t want to gnaw on a woody, 4 foot tall Japanese knotweed stalk, but the tender stems as they’re just beginning to re-emerge from the ground in the spring? Now those might be worth trying.

emerging stems of Japanese knotweed (Reynoutria japonica)

Japanese knotweed (Reynoutria japonica) was introduced to Europe from Japan in the 1800’s, arriving at Royal Botanic Gardens Kew by 1850. At that point, it was a prized ornamental. Its thick stems spotted with reds and purples, its broad, shiny leaves, and its showy flower heads all gave it garden appeal. It was also found to be useful for stabilizing hillsides and reducing erosion, honey production, and as a rhubarb substitute (it’s in the same plant family as rhubarb after all). Not long after that, it made its way to North America. Certainly people must have been aware of its propagative prowess as they moved the plant around. It readily roots from root and stem fragments, plus it produces extensive rhizomes, working their way as deep as 3 meters into the soil and as far as 7 meters away from the parent plant. Perhaps that should have been cause for alarm, but how could anyone have predicted just how aggressive and widespread it would soon become?

Thanks to the plant’s rhizomes, Japanese knotweed grows in thick, many-stemmed stands, pushing out, shading out, and leaving very little room for other plants. The rhizomes are also tough and can push up through gravel, cement, and asphalt. They are notorious for damaging foundations, pipes, and even pushing their way through floorboards. If that’s not enough, Japanese knotweed is pretty much impossible to kill. Herbicides may set it back, but they generally don’t take it out. Cutting it down repeatedly can slow it down, but it may also encourage it to grow more thickly and spread out more widely. Smothering it can work, but you have to be prepared to keep it smothered for quite a while. The deep rhizomes are slow to die, and they may eventually find their way outside of the smothered area, popping up to destroy your efforts to contain it. You can try to dig it out, but the amount of dirt you’d have to dig to get every last root and rhizome really isn’t feasible in most circumstances.

But hey, you can eat it, and perhaps you should. A quick internet search reveals a number of ways the plant can be consumed – purees, chutneys, compotes, sorbets. I chose to go with pickled Japanese knotweed. It seemed simple and approachable enough and a good way to determine if I was going to like it or not. Room temperature brine fermentation is pretty easy. You basically put whatever you’re wanting to pickle in a jar, add whatever spices and things you’d like, fill the jar with salty water, then seal it shut and let it sit there for a few days. Before you know it, you’ve got pickles.

There are several recipes for pickled Japanese knotweed to choose from. I went with this one. The seasonings I used were a bit different, and the stalks I had weren’t as “chubby” as recommended, but otherwise my approach was the same. After a few days, I gave them a try. I was pleasantly surprised. I thought they tasted a little like nopales. Sierra reluctantly tried them and was also surprised by how good they were. They reminded her of pickled asparagus. Other sources describe them as lemony, crunchy, tart and suggest serving them with fish, ramen, or even adding them to a cocktail made with purslane. Many of the weeds I’ve tried have been a fun experience, but not necessarily something I need to repeat. Japanese knotweed pickles, on the other hand, could become a spring tradition for me, and since we’re pretty much stuck with this plant, I’m sure to have a steady supply.

More Eating Weeds Posts on Awkward Botany:

Weeds of Boise: Awkward Botany Headquarters

Weeds of Boise: Awkward Botany Headquarters

Last December, Sierra and I left apartment living behind and embarked on a new journey as homeowners, which you can read about in this January’s Year in Review post. This means that Awkward Botany Headquarters now has a yard, and having a yard means we also have weeds.

For many people living in urban areas, the weeds of most concern to them are the ones found in their yards, especially for those that garden or like to keep a tidy yard. Removing weeds is a constant chore. They are always popping up and getting in the way of our plans. In fact, that’s the very definition of a weed – an uninvited plant growing in a location where it isn’t wanted. Despite our best efforts, our yards are always going to have some amount of weeds in them, so what better place to familiarize yourself with your wild urban flora than in your own yard? Or, in this case, our yard.

Our house is located in an area of Boise called the Bench. The Boise Bench, which is actually a series of benches or terraces, is located south of the Boise River and overlooks downtown Boise. The formation of the benches began 2 million years ago as the Boise River cut through the valley. Over time, sediments were deposited at the south bank of the river as it cut further and further northward, leaving behind the series of large terraces. Early in Boise’s history, the Bench was largely agricultural land thanks to the construction of canals. As the city grew, housing and commercial developments expanded across the Bench and have now displaced most of the farmland. Urbanization of the Boise Bench continues today at a steady clip.

While I haven’t had a chance to explore every square inch of the yard, and the growing season is just getting started, what follows are a few photos and a short list of some of the weeds I’ve encountered so far.

  • Arctium minus (burdock)
  • Bromus tectorum (cheatgrass)
  • Capsella bursa-pastoris (shepherd’s purse)
  • Cirsium arvense (creeping thistle)
  • Chondrilla juncea (rush skeletonweed)
  • Digitaria sanguinalis (crabgrass)
  • Draba verna (spring draba)
  • Echinochloa crus-galli (barnyard grass)
  • Elymus repens (quackgras)
  • Epilobium sp. (willowherb)
  • Erodium cicutarium (redstem filaree)
  • Euphorbia maculata (spotted spurge)
  • Hordeum murinum (wild barley)
  • Lactuca serriola (prickly lettuce)
  • Lepidium sp. (white top)
  • Malva neglecta (common mallow)
  • Poa bulbosa (bulbous bluegrass)
  • Polygonum sp. (knotweed)
  • Portulaca oleracea (purslane)
  • Sonchus sp. (sowthistle)
  • Taraxacum officinale (dandelion)
  • Tragopogon dubius (salsify)
  • Ulmus pumila (Siberian elm)
  • Veronica sp. (speedwell)

Like all posts in the Weeds of Boise series, this will be updated as I identify and photograph more of the weeds found in this location. Do you have a yard in an urban area? What weeds are you seeing in your yard this year? Let us know in the comment section below.