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Randomly Selected Botanical Terms: Tepals

The reason for flowers is reproduction. Three major parts of a flower function to achieve this purpose. First, the gynoecium sits at the center. This is the ovule-producing portion. It’s where seeds are born. Its stigmas accept pollen produced by the second major flower part, the androecium. This part is made up of a whorl of stamens that generally surround the gynoecium, except when the gynoecium and androecium are found in separate flowers. The third major part, known as the perianth, is not essential for reproduction yet present on the majority of flowers (wind- and water-pollinated flowers tend to be the exceptions).

The perianth is composed of two whorls: sepals and petals. Collectively, sepals are known as the calyx and petals are known as the corolla. Sometimes sepals are fused together to form a cup or tube shape, but often they are separate, leaf-like appendages. Same goes for petals. The function of the perianth is two-fold: protect the developing flower bud and announce to pollinators that the flower is ready to be pollinated. Ancillary purposes can include housing nectaries, holding seeds once they are formed, and becoming incorporated into the fruit. The perianth, along with the other two major flower parts, are important identifying features of plants when keying them out to genus, species, or family.

If you’ve spent time looking at flowers, you’ve probably found it fairly easy to distinguish sepal from petal. Sepals are typically smaller, green, and more leaf-like; petals are showier and more colorful. While sometimes sepals stand out among the petals, adding to a flower’s showiness, much of the time they are discretely hidden away on the backside of a flower. They encase the flower when it’s in bud and then remain at the base of the flower after it has bloomed.

Occasionally, however, sepals seem to be absent or difficult to distinguish from the petals. This is where the term tepal comes in. In certain groups of plants, mainly those that have a more ancient lineage, the perianth is made up of tepals. Rather than two distinct whorls, there is a single whorl or multiple whorls of tepals. Tepals are still protective and showy, serving the same function as individual sepals and petals, but they are not differentiated. They harken back to a time before the perianth had evolved into two separate whorls. In the Early Cretaceous, when they were the new kids on the block, flowers were in the process of developing intricate relationships with pollinators, and their features were generally less specialized than many of the flowers we see today.

snowdrop (Galanthus sp.)

One group of plants commonly known to have tepals is the monocots (or monocotyledons). Monocots have a single cotyledon (seed leaf), flower parts in multiples of three, and leaves with parallel veins. In the spring time, some of the best examples of monocots are spring bulbs. Take a look at the tulips, daffodils, crocuses, hyacinths, and others coming up in your neighborhood. Clearly they have petals, but where are the sepals? There are no leafy appendages surrounding the bases of the flowers. The “petals” of these plants are actually tepals.

fused tepals of hyacinth (Hyacinthus sp.)

In some descriptions for tulips, lilies, and others, you’ll find a reference to sepals. In other descriptions, there are references to outer tepals and inner tepals. This is because these plants have at least two whorls of tepals, and sometimes the outer whorl is referred to as sepals, yet both whorls look nearly identical. Tepals is a better term for these structures.

outer and inner tepals of Tulipa 

But what’s going on with daffodils? If the outer whorl is made up of tepals, what is the cup-like apparatus surrounding its sex parts? This structure is called a corona. It is an outgrowth of the hypanthium, which is a structure formed when the bases of the tepals and stamens fuse together. The corona grows out from this ring of tissue and creates what appears to be fused petals. While the corona functions like a petal, it is not a true petal since it is made up of hypanthial tissue.

tepals and corona of daffodil (Narcissus sp.)

Tepals are also common in plant species found in the clade magnoliids. The genus Magnolia is a classic example of this. The large showy petal-like structures of magnolia flowers are actually tepals. The protective role of sepals is carried out by a series of fuzzy bracts that surround the developing flower bud. After the flower has opened, the bracts fall away and are not persistent in the way that sepals typically are.

Magnolia sp.

Sometimes it can be tricky to determine whether or not a perianth is made up of tepals or sepals and petals. The buttercup family (Ranunculaceae) is a fun one to consider in this regard. The showiest flower parts of many of the species in this family are actually sepals, while petals are either reduced, modified, or entirely absent. When it is difficult to distinguish a sepal from a petal, the term tepal is often used, such as in the genus Clematis. Hellebores, on the other hand, are a unique case study. The large showy parts of a hellebore flower are petaloid sepals – sepals that are playing the role of petals. Hellebore petals are present but reduced and tube-shaped. They house the nectaries of the flower, drawing in early season insects looking for food. As visiting insects feed on the nectar found within these modified petals, they brush against the stamens of the flower and inadvertently move pollen around.

petaloid sepals of Helleborus sp.
petaloid sepals and reduced, tubular petals of Helleborus sp.

A simple way of describing tepals could be that they are sepals and petals fused together to form a single structure, but this would be an inaccurate description. Tepals are found on plants that have not evolved separate sepal and petal structures. As these flowers develop, gene expression does not differentiate the perianth into two distinct whorls. The term “tepal” is also used when it is difficult to distinguish the difference between petals and sepals, even when there may be a developmental difference. Whether looking at petals, sepals, tepals, or something entirely different, any excuse to take a closer look at flowers is okay by me.

More Randomly Selected Botanical Terms:

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Meet Liatris microcephala

The aster family has a lot to offer. It’s really no surprise considering that Asteraceae is the largest family of flowering plants in the world with as many as 33,000 species. Certainly its ecological importance is substantial. It also contains, arguably, some of the most beautiful and attractive plant species, as well as a significant selection of useful plants from a human perspective. When a plant family is this big, it is essential to subdivide it into smaller groups in order to better understand it. The subject of this post finds itself in a tribe within the aster family called the thoroughwort tribe or Eupatorieae – home to other familiar genera like Ageratina, Ageratum, Eupatorium, Eutrochium, Conoclinum, and Stevia.

Liatris is a North American genus that includes around 37 species and at least 12 naturally occurring hybrids. All of these species are found east of the Rocky Mountains – scattered across the Midwest, in the northeastern and southeastern regions of the United States, as well as north into Canada and south into Mexico. While there are a couple of species found within the Rocky Mountain region, there are no species of Liatris found west of the Rockies. One species is found in the Bahamas.

Commonly known as gayfeathers or blazing stars (not to be confused with the blazing stars of the Mentzelia genus in the family Loasaceae), Liatris is a group of perennial plants with upright, mainly unbranched stems that flower from the summer into the fall. After dying back to the ground in the winter, they emerge in the spring from elongated or globular corms, their narrow leaves giving the appearance of a tuft of grass. Flowers occur in the upper portions of upright stems and are held in bell-shaped or cylindrical involucres. They lack ray florets like those of a typical aster flower. Instead, each flower is composed only of a series of small disc florets which can give them a button-like appearance. Flowers come in shades of lavender, magenta, pink-purple, and rose-purple (sometimes white).

grass-like foliage of Liatris microcephala

Plants in this genus vary in height, with the tallest reaching over 5 feet. My affinity for diminutive plants draws me to some of the shorter plants in this group, particularly Liatris microcephala or smallhead blazing star. Other common names for this plant include dwarf blazing star and Appalachian blazing star. This species has very slender, linear leaves and looks a lot like a little bunchgrass for much of the growing season until its flower stalks start to emerge in midsummer. These stems can rise to 2 feet tall or more, but are often much shorter, especially in the lean soils that I grow them in here in Idaho. Linear leaves lacking petioles are alternately arranged along the length of the flowering stems. Flowers are rose-purple or lavender and composed of only 4 to 6 disc florets. They flank the upper portion of the upright stems, and gradually open from the top down from mid to late summer into the fall.

The fruits of Liatris are slender, ribbed achenes with a short, bristly pappus attached that is either feathery or barbed. The pappus of L. microcephala is minute and bristly. Once mature, the fruits detach from the plant and are blown around by the wind, sometimes grabbing on to the fur of passing animals.

smallhead blazing star (Liatris microcephala)

L. microcephala has a relatively limited natural distribution, occuring mainly in the southern Appalachian Mountains from western North Carolina and Kentucky, south to western South Carolina, north and central Georgia, and into northern Alabama. It prefers dry, rocky, slightly acidic soils, but can tolerate other soil types as long as they are well-drained. It prefers full sun and tolerates high heat and humidity. Its tendency to grow in rocky outcrops makes it a good rock garden plant. It is also used on green roofs. Like most other plants in this genus, L. microcephala needs well-draining soils particularly during the winter, as corms can rot out when they stay wet over prolonged periods.

A Chicago Botanic Garden plant evaluation report includes Liatris in a list of perennials that first gained popularity in European gardens before finding favor in the North American horticulture industry. In spite of being native to North America, gardeners on this continent looked to plants from other parts of the world to fill their gardens. Now, as trends shift towards native plants and habitat gardens, plants like native blazing stars which are visited by a variety of insect species and whose seeds are consumed by birds, are an obvious choice. They are relatively easy to grow and care for, and there is a wide selection to choose from, including cultivars. Though not native to the west, blazing stars are great plants for gardens in our region due to the drought-tolerance that is common in this group. Water conservation is of particular importance in the semi-arid west, and L. microcephala, with its penchant for growing on rocky outcrops is particularly drought tolerant. Apart from that, it’s just a beautiful, little plant and one that I will continue to grow, with the dream of someday seeing it in its natural setting.

smallhead blazing star (Liatris microcephala)

See Also: Meet Erigeron linearis

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Garden Plants Gone Weedy: Lawn Violets

When garden plants go weedy, it doesn’t necessarily mean they’ve escaped the boundaries of our yards and invaded nearby natural areas or uncultivated spaces. While this is a concern for a significant number of ornamental plants, sometimes the weediness of a garden plant is experienced within the very yard or garden it was planted in. For some of us, such a plant’s weediness can turn us off from growing it at all. We opt to weed out the overzealous plants and replace them with something tamer. Others may decide to just put up with this behavior. Perhaps we like the plant too much to get rid of it, so we simply accept its overly competitive nature. We may even welcome its ability to take any and all available ground. Why toil away trying to get something else to grow, when our weedy friends take up space with little to no effort on our part?

This seems to be the story of violets. While certainly not all violets exhibit this behavior – some species are actually downright difficult to grow – there are a select number of species that are proficient at propagating themselves and spread readily. They capitalize quickly on open ground and set up shop before anything else has the chance. Given the opportunity, they may even snuff out other plants and take their place. I’ve dealt with the latter myself, as violets moved in on some mat-forming penstemons and eventually took them out.

While violets can and will act aggressively in garden beds, ire towards their unruly behavior seems to stem largely from their activity in lawns. There is an expectation that lawns be grass species only, and any other plant that finds its way in gets labeled as an intruder that must be stopped. While some people tolerate (and even encourage) a few guests – which I think is a reasonable approach – others prefer grass and grass alone. Whatever your preference is, violets can become too much. Grass often has a difficult time competing with the broad, evergreen leaves of violets and their horizontally spreading rhizomes and stolons. As violet colonies expand, the grass succumbs, and broad patches of violets can become dominant in declining lawns.

At least three species of violets are particularly notorious for invading lawns in North America: Viola odorata, Viola sororia, and Viola riviniana. Sweet violet, or V. odorata, is a perennial plant from Eurasia that forms dense mats with the help of rhizomes and leafy stolons. Its leaves are oval to heart-shaped with toothed margins. Solitary flowers rise above the foliage on slender, hooked stalks. Flowers are white to various shades of purple and have a sweet scent. Common blue violet, or V. sororia, is native to North America and looks very similar to sweet violet. The two species can also hybridize. Common blue violet tends to have more heart-shaped leaves and broader flowers. It also produces only rhizomes, no stolons.

Dog violet or wood violet (V. riviniana) is another similar-looking plant from Eurasia that – depending on what source you reference – either does or does not spread by stolons. This confusion could arise if sprawling stems are rooting at the nodes and being mistaken for stolons, which almost seems like a distinction without a difference. If you’ve seen this plant in a garden setting, there is a good chance it is the commercially popular, purple-leaved form (V. riviniana Purpurea Group).

All of these violets flower in the spring, and sometimes resume flowering in the fall. Their fruits are capsules, which upon ripening split open and fling out several tiny, shiny seeds. There ability to spread readily both by seed and vegetatively is a reason they are so successful at getting around. And if that weren’t enough, they have a secret weapon called cleistogamous flowers. These are flowers that never open for cross-pollination. Instead, they remain closed and opt for self pollination. Their fruits ripen, split open, and release seeds, often coming equipped with elaiosomes – a little packet of food that encourages seed dispersal by ants. These cleistogamous flowers appear in late summer/early fall and are hidden below the foliage either at or below the soil. With so many options for reproduction and dispersal, its easy to see why lawn violets can frustrate many gardeners.

Viola riviniana Purpurea Group

Lawn invaders invade lawns because they are adapted to the conditions found there. Lawns are often well-watered, so the soil stays moist. The soil is also generally compacted due to regular foot traffic, etc. Plants with low growing foliage escape the blades of mowers, which would kill or set back other weeds with more upright foliage and stems. These are all reasons why violets take well to turfgrass. They tend to prefer shady, cool, moist locations, but can also tolerate full sun and dry soils. Once they have gained footing in a shady part of the lawn, their superb ability to reproduce and spread allows them to expand their territory, particularly in lawns that are poorly maintained. Luckily, their roots are shallow and the plants are easy enough to dig up and remove. If you are tenacious enough, they can be largely eliminated. Or, just learn to accept their presence and appreciate them for their carpet of attractive flowers in the spring and their broad, evergreen leaves year-round. It could be worse.

More Garden Plants Gone Weedy:

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Tea Time: Self-heal

Prunella vulgaris can be found all over the place. It has also been used to treat just about everything. What else would you expect from a plant known commonly as self-heal, heal-all, all-heal, and woundwort? The medicinal value of this plant has been appreciated for centuries across its expansive range, and studies evaluating its medicinal use continue today. Being such a ubiquitous species – both as a garden plant and a native plant (and also a common weed) – and because it has so much clout in the world of herbal medicine, it’s an obvious candidate for Tea Time.

Self-heal is a member of the mint family (Lamiaceae), easily distinguished by its square stems, opposite leaves, and bilabiate and bilaterally symmetrical (or zygomorphic) flowers. One surprise is that, unlike the many aromatic members of this family, the foliage of self-heal lacks a strong scent. P. vulgaris occurs naturally across Asia, throughout Europe, and in parts of northern Africa. It is also widely distributed across North America. Apart from that, it has been introduced to many regions in the southern hemisphere and has also been frequently moved around throughout its native range. Eurasian varieties now intermingle with North American varieties, which can make it difficult to determine a native individual from an introduced one.

self-heal (Prunella vulgaris)

Self-heal is an adaptable plant that tends to prefer shady, moist locations, but can also be found in open, dry, sunny sites. Find it along forest edges, roadsides, ditches, and trails, as well as on the banks of streams, lakes, and reservoirs. It occurs in gardens, both intentionally planted and as a weed, and can escape into lawns, vacant lots, and open fields, as well as into nearby natural areas.

P. vulgaris is an evergreen that grows both prostrate and upright, sometimes reaching 1 foot tall or more (but is often much shorter). It has shallow, fibrous roots, and its stems root adventitiously as they sprawl across the ground, frequently forming an extensive mat or groundcover. Its leaves are oval to lance-shaped and measure about one inch long. Lower leaves have petioles, while upper leaves may become stalkless. Leaf margins are entire or can be slightly toothed. As plants age, they can develop a coppery or purple-bronze color.

the leaves of self-heal

The flowers of self-heal are generally a shade of purple, but can also be white, pink, or blue. They bloom irregularly in a spike measuring up to two inches long. Flower spikes are thick, dense, cylindrical, and made up of whorls of sharp-pointed bracts. Flowers bloom irregularly along the spike and occur from late spring/early summer into the fall. Each flower produces four nutlets, which sit within a cup-shaped, purple calyx.

As a medicinal herb, self-heal has been used both internally and externally to treat a long list of ailments. These include sore throats, diarrhea, fevers, intestinal infections, liver problems, migraines, heart issues, dermatitis, goiter, and thyroid disfunction, just to name a few. It has been used topically to treat skin irritations, bites, stings, and minor cuts and scrapes. This is thanks to its antimicrobial properties and its ability to stop bleeding. A report in the journal Pharmaceuticals (2023) calls P. vulgaris an “important medicinal plant” due to its “rich chemical composition” and its “pharmacological action.” Chemical analyses find the plant to be a valuable source of phenolic compounds, flavonoids, rosmarinic acid, and ursolic acid, among numerous other compounds. If you are curious to learn more detailed information regarding this plant’s medicinal value, you can refer to the above report, as well as one found in Frontiers in Pharmacology (2022).

self-heal tea

P. vulgaris is an edible plant, and its young leaves can be eaten raw or cooked. The leaves together with the flowers can also be dried and used to make a tea. This is how I had it. I used about two teaspoons of dried leaves to one cup of water. Feel free to use more if you would like. I thought the tea was pretty mild. It had a slight sweetness to it and a hint of mint flavor. It has been described as bitter, but I didn’t find it to be overly so (although I may have a higher tolerance for bitterness). Sierra tried it and said that it tasted like “water left over from something else.” That might be because it was more diluted than she would have preferred. Overall, I thought it was a pleasant experience and would be happy to drink it again.

More Tea Time Posts on Awkward Botany:

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Garden Plants Gone Weedy: The Periwinkles

In a garden setting, a successful groundcover is a plant that is durable and adaptable, spreads readily, and fills in space thouroughly. The point of planting a groundcover is to cover exposed soil and create a sort of living mulch. In fact, groundcovers provide similar benefits to mulch. They prevent erosion, help retain soil moisture, and prevent weeds. It should come as no surprise then, that a plant that fulfills all of these requirements has the potential to become a weed, especially if given the opportunity to escape and establish itself outside of its intended location.

This isn’t a hypothetical. This exact scenario has played out numerous times. A good example of this are the periwinkles: Vinca major and Vinca minor. Both have been popular garden plants for centuries. Their introduction to U.S. gardens came as early as the 1700’s. Today, both species (including cultivars of each) can be found for sale in nurseries throughout the country, even while escaped periwinkles proceed to spread across natural areas and uncultivated spaces. Even in gardens where periwinkles have been intentionally planted, they can be deemed no longer welcome due to their aggressive nature. Eliminating them, however, is a formidable task.

greater periwinkle (Vinca major)

Periwinkles are relatively easy to identify, yet telling the two apart can sometimes pose a challenge. Knowing what to look for can make this a fairly simple task. Vinca major (greater periwinkle) is the larger of the two. Its stems are tough and sprawl up to 5 feet long, rooting adventitiously when in contact with the ground. Vegetative spread also occurs via stolons and rhizomes, modified stems that spread horizontally both above and below ground and whose main purpose is to produce new roots along their length. This extensive rooting creates dense mats of stems and foliage, precisely what you’d want from an effective groundcover. Leaves are arranged oppositely and are semi-evergreen with fine hairs along their margins. They are thick, glossy, simple, dark green, and ovate to ovate-lanceolate in shape. They have a relatively long petiole, and some leaves can even appear heart-shaped.

The flowers of V. major are blue to purple and fused at the base to form a tube, separating into five distinct lobes and creating a shape similar to a pinwheel. They are borne on a long stalk in the axils of leaves and measure about two inches wide. Their sepals are long, slender, pointed, and lined with bristly hairs. Fruits rarely form, but when they do, they are narrow follicles.

comparing the petals and sepals of Vinca major (left) and Vinca minor (right)

Vinca minor (lesser periwinkle) is a slightly smaller plant with a similar habit, spreading vegetatively in all the same ways as V. major. Stems are slender and smooth and leaves are evergreen. Compared to V. major, the leaves of V. minor are smaller, narrower, and have hairless margins and short petioles, otherwise they are very similar. Same goes for the flowers, which look identical on both species, except that those of V. minor are slightly smaller (about one inch wide) and borne on shorter stalks. Sepals are shorter, broader, more rounded at the tips, and lack the bristly hairs of V. major.

Because periwinkles only rarely produce seed, their main method of getting around is vegetatively. Fragments of roots or rhizomes hide in soil and are moved from one location to another inadvertently. Periwinkles are often used in hanging baskets and containers, and when these things are cast aside at the end of a season, the perennial roots of periwinkles may continue to grow, spreading out beyond the potting mix and into the soil.

Dump soil, yard waste, and improperly disposed of containers are the main ways that periwinkles find their way into natural areas. Both species can be found in the understories and edge habitats of woodlands, as well as along roadsides and pathways, and in vacant lots and old homesites. They can also be found in riparian areas, where waterways can carry fragments of plants to new locations. The Invasive Plant Atlas compiles reports of both V. major and V. minor growing outside of cultivation and tracks them on a map. They also track which states include them in noxious weeds lists or laws.

lesser periwinkle (Vinca minor)

The best way to keep periwinkles from continuing to spread outside of cultivation is to refrain from growing them. If you choose to have them in your yard, dispose of plant parts properly. If you keep them in containers, send those containers to the landfill when you are done with them. If your property is adjacent to natural areas, the risk may be too great and you may want to consider a different groundcover. Depending on where you live, alternatives vary. In the Intermountain West, potential substitutes include wild strawberry (Fragaria virginiana), woodland strawberry (F. vesca), kinnikinnik (Arctostaphylos uva-ursi), and wild ginger (Asarum caudatum). Each of these are low growing, evergreen to semi-evergreen, spreading plants that do well in shade and can handle some degree of drought.

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Horticulture’s Weedy Introductions in a Changing Climate

In case I need a reminder that the horticulture industry has a history of introducing weedy plants to natural areas, I get one each time I bike to work. Riding along the Boise River Greenbelt, a trail that for much of its length is flanked by cultivated landscapes on one side and a highly modified but largely naturalized river bank on the other, I see a mixture of both native and introduced plants. Of the introduced plants, many are horticultural species that have escaped cultivation and established themselves on the bank of the river. There are catalpa and black locust trees brought in from the other side of the country, St. John’s wort and chicory from Eurasia, honeysuckles primarily from Asia, and a few different cherry species and hybrids with varied provenances. And this is just a small sample of what can be found along my three and a half mile bike ride.

St. John’s wort (Hypericum perforatum) on the banks of the Boise River

This is certainly not a new concern. We have been aware of the role that horticulture plays in introducing invasive species for quite some time now. Several years back, while doing a deep dive into the topic of invasive species, I wrote about this issue right here on this very blog. According to a study published in Frontiers in Ecology and the Environment (2021), out of 1285 plant species identified as invasive, 61% are currently sold in nurseries. If that’s not concern enough, an additional factor to consider is climate change. Plants that were less likely to escape cultivation and head for the wild, may take the opportunity to do so in a changing climate. Plus, horticultural plants that are already problems in certain areas could expand their range as climates become more favorable in new locations, especially if these plants continue to be sold in nearby nurseries.

These concerns and more are the topic of a paper published in BioScience (2023). Evelyn M. Beaury, et al. looked at nurseries across the United States and the plants they sell in order to determine where invasive plants are still being sold in regions where they are invasive. Additionally, they looked at plants known to be invasive but that are not currently invasive in the regions they are being sold. Using climate models, they predicted whether or not these plants could become invasive under changing climates.

Plants are being moved around with a lot more ease than they once were, and the sales of problematic plants are increasingly difficult to regulate. For one thing, plants prohibited for sale in one state can be purchased at nurseries in neighboring states and brought back to be planted in regions where those plants are invasive. And while mail order has existed for a long time, online ordering makes the process even simpler; and many online plant vendors are not liscensed nurseries, making them much more difficult to regulate. But even regulation is typically a response to something that has already become a problem, rather than a proactive measure to prevent plants from escaping into natural areas.

Beaury, et al. identified 672 nurseries across the United States, both online and traditional retailers. Each of these nurseries were selling one or more of the 89 plant species that became the focus of their research. These are plant species that are either on federal or state noxious weed lists or that have been identified as invasive by Invasive Plant Atlas. The reach of each nursery was determined by using customer reviews to compute distances that plants might travel after being purchased at nurseries or from online stores. Obviously, not every customer that purchases a plant leaves a review, but this is a good way to get a general idea how far away customers are from nurseries without having access to more detailed records. These geotagged reviews can also be cross-referenced with known distributions of invasive plants. Using climate models and environmental predictor variables, the researchers determined areas of current and potential invasion for each of the 89 plants.

tansy (Tanacetum vulgare) – one of the 89 plant species looked at in the study

The first question was about proximity to current records of plant invasions. Results showed that “49 of the 89 ornamental invasives were sold within 21 kilometers (13 miles) of an observed record of invasion.” When invasive plants are sold and planted near locations where they are already known to be invasive, it gives them the opportunity to add new plants to existing or developing invasions. In ecology, this is known as propagule pressure. When it comes to current and future climate, most species in the study are being sold by nurseries where the climate is either currently favorable for range expansion or may eventually become favorable. Specifically for future climate, 40 of the 89 plants are being sold in regions that are currently suitable for invasion and will continue to be suitable as the climate changes, and 25 of the 89 plants are being sold in regions where the climate is currently unsuitable but will become suitable as temperatures warm.

Particularly for plants being sold in areas that are not yet suitable for invasion, there is time to educate both the nursery industry and the general public and to look for alternatives to these plants. However, as the researchers point out, their analysis “only examined about 10% of the larger pool of U.S. ornamental plants known to be invasive,” and they “sampled only a subset of the nurseries that could be selling invasive species in the United States.” It is highly likely that the results of this study are an underestimation of the problem. Clearly the work of education and finding alternatives to problematic plants is monumental. The hope is that studies like this can help with education and can assist with working out ways to regulate sales of invasive plants.

coltsfoot (Tussilago farfara) – another one of the 89 plant species looked at in the study

Regulating the sale of plants is beyond most of our control, and how much regulation we should be enforcing on nurseries in the first place is a debate we should be having. Outside of those questions, there is a responsibility that we should take as gardeners and as residents of the planet. If we choose to grow plants, it is crucial that we get to know them. We should be taking the time to observe the degree to which they spread and how they are being dispersed. When they do move around our yards, where are they going, and are they able to grow outside of our care? Are they leaving our properties and coming up elsewhere? If we choose to plant non-native species, we should be mindful of how they might affect nearby, wild landscapes if they were to escape our yards and establish themselves in these locations. We should also be aware of where we live in the city. If our gardens are in the middle of a dense urban landscape, perhaps there is less concern that our plants will move beyond the borders of our gardens. But if we garden near natural areas, we should be significantly more selective about the things we plant, and we ought to be more observant as to what those plants are up to.

Nurseries generally sell the plants that gardeners want to buy, which means we can choose not to buy problematic plants and instead demand alternatives to these plants. Seeking out nurseries that sell the types of plants that are better suited for our regions and do not exhibit invasive behaviors can send a message to other growers that they should phase out certain plants and start growing the plants that gardeners are asking for. This may be a simplistic take, and as with most things, it’s complicated. While one of the goals of this research is to help influence regulators, another goal is simply to “[share] information about high-risk ornamental invaders across states and regions, and [work] with horticulture and community members to reduce the escape of ornamental species into natural areas.” This is precisely the area where gardeners can make a difference.

On that note, I will be starting a new series of posts to discuss some of the ornamental species that have gone weedy. By getting to know the plants that find themselves in this predicament, we can be better situated to make informed decisions about what to do about them.

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2024: Year in Review

Happy 2025! Apparently it’s time for another year in review. As I said in last year’s review, 2024 was going to be another year of pollination, in which I would write monthly posts on the topic of pollination. Well, clearly that didn’t happen. After two posts, I dropped the ball. That’s okay though. Another Year of Pollination will continue indefinitely. As it is, I essentially stole the name, Year of Pollination, from a podcast called Year of Polygamy, which after starting in January 2014, continues to put out episodes a decade later. A “year,” as it turns out, can also be a period of indefinite length.

2024 wasn’t the most fun year I’ve ever had. I’m actually happy to see it go. Hoping for bigger and better things in the year to come. However, one very exciting piece of news came near the end of the year, which I hinted about in this post. The past couple of months have been a bit of a blur as I have been writing furiously about weeds for a book project that should come out sometime in 2026. Something to look forward to. It is focused specifically on the Pacific Northwest, so if there are any weeds-interested people in the area that would like to help out in some way with this project, please reach out.

The book will keep me busy for a good part of the year, so I don’t anticipate being able to post a whole lot more here than I have in the past couple of years. But I’ll see what I can do. Be in touch either way. All the social media links and ways to support Awkward Botany can be found on this link tree. Thank you, as always, for reading and nerding out about plants with me. See you in 2025!

Most of the posts this year were part of ongoing series. So, here they are:

Winter Trees and Shrubs

Another Year of Pollination

Randomly Selected Botanical Terms

Book Review

Weeds of Boise

Things really took a turn in 2024. Let’s see what 2025 brings…
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Winter Trees and Shrubs: Box Elder

Box elder is a maple that doesn’t often get credit for being a maple. Moreso, it is a tree that is not thought highly of, and it may not even be welcome in certain discussions around maples. You could even say that box elder is a “rogue maple,” as Arthur Plotnick deems it in The Urban Tree Book. It should come as no surprise, but if people are going to talk about a plant this way, it’s only going to make me like it more.

First off, the leaves of Acer negundo are palmately compound, compared to the simple, palmately lobed leaves of other maples. A box elder leaf is generally composed of three leaflets, sometimes five or seven. The center leaflet is on a longer stalk than the side leaflets, which are oppositely arranged. Sometimes the leaves are confused with ash tree leaves (Fraxinus spp.), which is the reason for another common name, ash-leaved maple. It’s also not uncommon for box elder leaves to be mistaken for poison ivy, which is maybe not a plant you’d want to be confused with. In the fall, unlike the beautiful reds, oranges, purples, and yellows of so many other maples, the leaves of box elder turn a drab yellow before dropping, a trait that Plotnick calls “an embarrassment.”

leaf of box elder (Acer negundo)

It’s not really its leaf, however, that bothers people. Box elder is a fast-growing and prolific tree. Basically, it’s weedy, and because it grows so quickly, its wood is generally weak and its structure unpredictable. It falls apart easily, and it doesn’t always grow in typical tree fashion. Sometimes its more of a shrub, and sometimes it leans so far over that it practically lies on the ground. It sprouts and suckers in abundance, and as John Eastman puts it in The Book of Forest and Thicket, it “generally ignore(s) human standards for an attractive tree.”

Maybe before people knew better, or during a time when people just needed a fast growing tree to plant in their developing cities, box elders were widely planted across North America and beyond. That and their ability to spread readily helps to obscure their native distribution. Box elder is naturalized across North America, but its original distribution (whatever that means) appears to be more midwestern and eastern. Box elder grows in a variety of conditions, and is actually quite drought tolerant, which has allowed it to feel right at home in the American west, whether it is truly native here or not.

Identifying box elder in the winter can be pretty easy, especially if you come across a seed-bearing individual. Box elders are dioecious, meaning male and female flowers occur on separate individuals (another thing that sets them apart from other maples). A samara-bearing tree is a female tree, and the samaras often hang from the branches in great numbers. Like other maples, the fruits are paired together, each seed with a prominent wing. The samaras of boxelder point downward and hang from long stalks, persisting on the tree throughout the winter.

persistent samaras of box elder

The twigs of box elder are glaucous (covered with a thin, powdery bloom) and can be either green, bluish-white, or reddish-purple. They have tiny, white lenticles, and their buds are oppositely arranged. Leaf scars are a broad U-shape, and scars opposite of each other meet at the tops of the U’s, coming to a raised point. At least three bundle traces (sometimes more) are visible in the scar. Leaf buds are protected by two scales that are covered in dense, white hairs. The scales are similar in color to the twigs, but appear more white due to the fuzz. Lateral buds are 1/8 inch long or longer. Slicing open the twigs lengthwise reveals solid, white pith in the center that blends in easily with the wood.

winter twigs of box elder
winter twigs of box elder, pith exposed

The bark of young box elders has slight vertical ridges and is light brown or grey-brown, with dull orange, raised, wart-like lenticels. It is finely scaly. The scales and ridges become more rough and blocky as the tree ages. Mature bark is light brown to grey and heavily furrowed, with blocky segments breaking apart horizontally.

maturing bark of box elder

A few years ago I was introduced to a massive box elder in Boise, Idaho. It quickly became my favorite tree in the area, and I visit it frequently. For all the hate that box elder can receive, seeing its potential to create an experience that few other trees in the area offer can send all of that negative talk out the window. Visit something like it yourself sometime, and see what it can do for you.

massive box elder

More Winter Trees and Shrubs:

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Weeds of Boise Takes a GIS Course

Why has this blog been so quiet lately? There are plenty of excuses for that. It doesn’t really matter either way, but since we’re on the subject, one thing that has kept me occupied recently is being back in school. I’m working on a certificate in GIS, and I’m hoping to make some cool maps. More on that later perhaps.

For now, I thought I’d share one of my final projects. I figured it was a good excuse to use something I’ve already been working on – namely, Weeds of Boise – and apply it to one of my GIS classes. If you’ve been following Weeds of Boise, not much here will be new. Except the interactive maps!

Using observations from iNaturalist, I created three different maps of weeds found around Boise. I published them, using ArcGIS StoryMaps, alongside more of my usual pontificating about weeds and urban areas, etc. The maps aren’t perfect, but they opened up some interesting possibilities for what Weeds of Boise might become. Something to explore further in the future.

Until then, here is a link to the project if you’d like to take a look: Wild Urban Flora of Boise Idaho.

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New Weeds Project, etc.

When you make yourself the weeds guy, and the word gets out that you’re the guy to go to when it comes to weeds, invitations and inquiries start coming your way. Usually it’s just someone asking you to identify a weed or telling you how much they despise a particular plant for its weedy behaviors. Sometimes it’s writing a weeds-themed article or teaching a class about weeds. It can even be an invitation to go on a weeds walk and be interviewed for a television series. This time it’s something, perhaps, a bit bigger.

I won’t say too much about what the project is at this point. It’s a little too early in the process for the big reveal. However, I will say that it involves at least two things: weeds and the Pacific Northwest. That’s partly why I’m bringing this up.

Do you live in the Pacific Northwest? Would you be interested in talking about weeds sometime? If you’re reading this, and you think you might have some input on the subject, please let me know. You can get in touch using the contact form or by sending me a direct message on Instagram. I can give you more information at that point, and we can determine if there is a way you can help.

There will be more to come about this exciting new project in the near future. Meanwhile, my lack of posting, which you may or may not have noticed, is likely to continue for a while. Summers get pretty busy around here, and as much as I’d like to share more posts with you, it just doesn’t happen. The fact that I’m basically back in school for a couple semesters, along with this new opportunity that I’m not saying much about, has made it so that focusing on the blog isn’t getting much easier. But I’ll do what I can, and I’ll try to stay active on Instagram and other social media sites to (sort of) make up for it.

Thanks, as always, for your support, and thank you for putting up with this announcement about an upcoming and soon to be announced announcement.

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