RANUNCULACEAE – the buttercup family

by Adriana Lopez-Villalobos and Amelie Mahrt-Smith

The Ranunculaceae family is more commonly known as the buttercup family, which is reminiscent of some of the shiny yellow members of the Ranunculus genus. The buttercup family may be considered “simple” from an evolutionary standpoint, because the floral parts – the petals, sepals, stamens and pistils – are all distinct and not fused in any way. Moreover, reproductive parts are often of an indefinite number as compared to other plant families with predictable numbers of three, four, or five. Some flowers, such as in the columbine, delphinium and clematis have flowers that might look highly complex, but they are still considered “simple” because all the parts are independently attached. There is quite a bit of variation in this family in terms of the number of sepals (3-15), petals (0-23), and stamens; however, for identification, one common pattern to look for is the multiple pistils (3 to more) in the centre of the flower, each with its superior ovary (hypogynous). Some members of the Rose family also have multiple pistils, but they have a hypanthium, a cuplike structure from which the sepals, petals and stamens all arise (perigynous flowers). The leaves are also different in that the roses will often bear prominent stipules, a feature lacking in the Ranunculaceae (Elpel, 2004). For examples of these differences click | here |.

Over the last few weeks, we have seen several examples of species from this family in Kingston. This week we decided to give a turn to two species native to Canada: the red columbine and the Canada anemone.

Aquilegia canadensis (Canada columbine)

A garden favourite, this member of the Ranunculaceae family is native to North America! Aquilegia canadensis, also known as the red columbine, wild columbine, or Canada columbine in English, is probably more familiar as a colourful addition to a carefully tended garden than as a weed. Outside of the city, you may be able to find this short-lived, spring-flowering perennial plant on rocky outcrops, dry woods, slopes, ledges or open areas, but in urban areas like in Kingston, it has been mostly crowded out of untended space by more competitive invasive species like garlic mustard (Alliaria petiolata; see our Blog post from June 9th, 2020). It has been suggested that the name Aquilegia is derived from the Latin word Aquila, meaning Eagle, possibly because of the flower’s spurs’ resemblance to an Eagle’s talon.


Aquilegia canadensis along sidewalk
Aquilegia canadensis amongst the foliage in Kingston, ON.

Columbine flowers are showy and unique, each petal having a long narrow spur at the back. The leaves grow in leaflets of 3 with deep lobes. The Canada columbine can be differentiated from similar columbine species like the European columbine (A. vulgaris) by its scarlet flowers with a yellow centre, and its stamens, which are long and protrude from the flower; the European columbine’s flowers are typically blue, purple, or white, and their stamens are not protruding (Newcomb 1977). Canada columbines can grow in a wide range of well-drained soil and can tolerate moderate shade. As well, this species is said to have good resistance to leaf miner beetles, which often cause damage to other species of columbines. For some tips on growing A. canadensis in your garden, as well as a shortlist of some other columbine species native to Canada, see | here |

Two species of Aquilegia
Left: Aquilegia canadensis, native to North America; Right: Aquilegia vulgaris, the garden cultivar introduced from Europe.

The columbine flower produces nectar in its spurs, which attracts a variety of pollinators, including the ruby-throated hummingbird (Archilochus colubris). It is also a food source for the rusty-patched bumblebee, Bombus affinis, an endangered species of bumblebee native to Ontario whose numbers have declined due to several ecological factors, including habitat loss (Macior 1966). Although the rusty-patched bumblebee has not been seen in Ontario outside of the Pinery Provincial Park since 2002, there are many other native species of bumblebee that would appreciate some Canada columbines to snack on in your garden! This includes some threatened North American bumblebee species such as B. fervidus and B. pensylvanicus, as well as the hummingbird clearwing moth (Hemaris thysbe). Although it might seem logical to think that A. canadensis would reproduce primarily via outcrossing, genetic analysis using progeny arrays from populations across its range have shown that approximately 75% of its seed, on average, are the product of self-fertilization. Thus, Canada’s columbine has a mix-mating or selfing mating system, rather than outcrossing (Eckert and Herlihy 2004).

Queen’s Biology faculty member Dr Chris Eckert has investigated several aspects of A. canadensis life history, floral morphology, ecology and evolution; some of his research on A. canadensis conducted at the Queen’s University Biological Station can be found on the QUBS Research Projects website. In recent years, the genus Aquilegia has become a model system for the study of floral evolution and development because of its unusual floral morphology and the recent explosion in the number of species associated with pollinator shifts and other ecological factors. To take advantage of these features, a collaborative group has developed several genetic and genomic resources that have facilitated the study of the genetic basis of these morphological innovations (Kramer 2009).

Canada Anemone (Anemonstrum canadense)

The Canada anemone, or ‘windflower’, is an inconspicuous member of the Ranunculaceae family in flower this month. They are not quite as abundant in urban areas as some other introduced ranunculus species, such as the common or tall buttercup (Ranunculus acris), the creeping buttercup (Ranunculus repens), or other common garden escapees, but you may still stumble across this low white flower in the Kingston area. The name ‘anemone’ is an Ancient Greek word meaning ‘daughter of the wind’. Ironically, this species prefers sites protected from wind since strong winds can bend or break the thin flower stalks.

This species was, until recently, part of the Anemone sensu lato (in the broad sense) genus and is often still called by its synonym Anemone canadensis. However, recent molecular phylogenetic analyses revealed that there were many more species and genera that needed to be included in the genus to satisfy the criterion of monophyly. Instead of renaming hundreds of species and including morphologically different genera such as Clematis (virgin’s-bower), Pulsatilla or Hepatica, the Anemone genus was regrouped into several genera, one of them being Anemonastrum, where Canada anemone is currently placed (Mosyakin 2016).

Canada anemone
The Canada anemone along the wet, rocky shores of Lake Ontario in Kingston.

The leaves of the Canada anemone have 3-5 deep lobes and toothed edges, and they have long stalks that emerge from a clump at the base. The flowers are white with many yellow stamens in the centre bearing pollen that attract pollinators. The notable features of the flower are the white petal-like sepals, usually 5 per flower. Sepals are a division of the outer part of the flower called the calyx and are often green and resemble leaves; whereas petals are a division of the inner part of the flower called the corolla and are often showy and attract insects. In A. canadense there are only sepals (modified to look like petals) and the petals are absent.

closeup of the Anemone flower
A closeup of the Anemone flower – notice the five white sepals and numerous yellow stamens.

The Canada anemone typically inhabits river margins, low moist meadows,and thickets. In nature, it can be found growing in massive colonies, and in cultivated areas is a common garden escapee. It is distributed throughout southern Canada from Newfoundland to British Columbia and in the U.S from Maine to Montana south to West Virginia, Missouri, Kansas and scattered through the Rocky Mountains to New Mexico. It is a perennial that can grow in semi-shaded areas and makes a beautiful addition to gardens while also benefitting the ecosystem by supporting native pollinator communities! Keep an eye out for this wildflower throughout the summer months around Kingston, ON – it is more than just a weed.

Ethnobotanical and medicinal uses

A predominant property in the plants of the Buttercup family is an acrid protoanemonin glycoside oil. Most of the species are listed as poisonous, but most are safe to taste, as long as you spit it out! The buttercup taste is biting and acrid, and its strength varies between species. The acrid properties of the buttercups are unstable and are destroyed by drying or cooking, so the very mild buttercups are edible as salad greens or potherbs. Plants in the buttercup family have been studied for possible medicinal use since the 1900s. The chemical compound protoanemonin has irritant but also antibiotic properties. The Pawnee peoples of what is now Oklahoma used A. canadensis to treat headaches, and closely related species had medicinal uses ranging from topical wound care to reviving unconscious people (Turner 1984). A. canadense was used by many Indigenous peoples in medicine. Traditional knowledge about the plant’s properties and how to prepare them for medicinal use is paramount – one risks further discomfort and injury from improper use of traditional medicine. The Ojibwe, an Anishnaabe peoples who have inhabited the Great Lakes region for thousands of years, used A. canadense and other closely related species of Ranunculaceae as a poultice or wash to treat superficial wounds, as a remedy for colds and headaches, and for the revival of unconscious people (Turner 1984).

Using herbarium specimens to understand phenology

As the negative impacts of human activities on ecosystems become deniable, and more pressing to attend than ever, researchers need biological data spanning hundreds of years to understand how anthropogenic drivers affect biodiversity and natural resources. Changes in the timing of key life-history events, such as reproduction (flowering and fruiting) are among the most obvious and well-documented species responses to climatic change, especially for plants. In recent years, the scientific community has started to turn their attention to hundreds of millions of plants, fungal and animal specimens deposited in natural history museums as a potential source of these data. The increasing number of museum specimens becoming available online combined with newly developed web-enabled crowdsourcing platforms (i.e. CrowdCurio) and protocols for scoring and analyzing phenological data provide unparalleled access to ecological and evolutionary data spanning decades and sometimes centuries. Park et al. (2019) capitalized on the snapshots of phenology (i.e. flowering and fruiting) that herbarium specimens offer to increase the spatial, temporal and taxonomic diversity of phenological studies. They used 7,722 herbarium specimens from 30 flowering plant species with varying life-history traits, growth forms, native status and general reproductive seasonality (e.g. early- versus late-spring flowering), spanning 120 years and modelling to understand how phenology changes in response to climate change. Their study included the red columbine and Canada anemone!
Their results showed that early-flowering species flowered and fruited earlier in response to warmer spring temperatures and that the magnitude of these responses varies significantly between and within species across their latitudinal ranges. They also found that fruiting in populations from warmer, lower latitudes are significantly more phenologically sensitive to temperature than that for populations from colder, higher-latitude regions.

By bringing you these bits of information from the scientific literature we want to raise awareness of these unparalleled resources. Herbaria and natural history museums are under constant threat owing to budget cuts and other institutional pressures. Like the study by Parker et al. (2019), more publications out there are shedding light on the unique discoveries that are possible using museums specimens, and thus, pointing to the singular value of natural history collections in a period of rapid change.


  1. Eckert, C.G., Herlihy C.R. 2004. Using a cost-benefit approach to understand the evolution of self-fertilization in plants: the perplexing case of  Aquilegia canadensis  (Ranunculaceae). Plant Species Biology 19:159–173
  2. Elpel, T. J. 2004. Botany in a Day: The Patterns Method of Plant Identification. HOPS Press.
  3. Kramer, E. M. 2009. Aquilegia: A new model for plant development, ecology, and evolution. Annual Review of Plant Biology 60: 261 – 277.
  4. Macior, L.W. 1966. Foraging behavior of Bombus (Hymenoptera: Apidae) in relation to Aquilegia pollination. American Journal of Botany 53: 302 – 309.
  5. Mosyakin, S.L. 2016. Nomenclatural notes on North American taxa of Anemonastrum and Pulsatilla (Ranunculaceae), with comments on the circumscription of Anemone and related genera. Phytoneuron 79: 1 – 12.
  6. Newcomb, L. 1977. Newcomb’s Wildflower Guide. Little, Brown and Company. New York. pp. 228.
  7. Park D. S., Breckheimer I., Williams A. C., Law E., Ellison A. M., Davis C. C. 2018 Herbarium specimens reveal substantial and unexpected variation in phenological sensitivity across the eastern United States. Phil. Trans. R. Soc. B 374: 20170394.
  8. Turner, N.J. 1984. Counter-irritant and other medicinal uses of plants in Ranunculaceae by native peoples in British Columbia and neighbouring areas. Journal of Ethnopharmacology 11: 181 – 201.

The pea family – FABACEAE

by Adriana Lopez-Villalobos and Amelie Mahrt-Smith

Clovers, medick, trefoil, lupines, vetches and beans are all members of the Fabaceae family, also known as the Pea family. These plants have a special trick that few other plants do – they can fix nitrogen, and thus help your garden grow!

By forming beneficial associations (called symbiosis) with some of the bacteria found in soil, legumes can obtain nitrogen much more easily than other plants. Root nodules containing the bacteria Rhizobium (collectively known as rhizobia) ‘fix’ free nitrogen for the plants, converting it into an easily usable form. And in return, the legumes then supply the bacteria with valuable carbon produced by photosynthesis. Nitrogen is one of three major nutrients that plants need to survive and thrive. The other two are phosphorus and potassium. When you buy a bag of fertilizer, you may notice three numbers (for example, 24-0-4); these numbers refer to the ratio of nitrogen to phosphorus to potassium. Plants usually get nitrogen through their roots directly from the soil, but by associating with ‘nitrogen-fixing’ bacteria, which can fix nitrogen from the atmosphere, legumes do not have to compete with grasses and other weeds for the nitrogen in the soil. Their deep roots store nitrogen, and when they die it becomes available to the surrounding plants. In this way, they help other plants grow by adding nutrients to the soil.

In this week’s post, we highlight some of the common species of Fabaceae growing in the streets in of Kingston, Ontario.

True Clovers – The Genus Trifolium (White and Red Clovers)

The pink and white flowers dotting lawns are a tell-tale sign that summer is on its way. These familiar weeds are just a few of the dozens of species in the genus Trifolium – “the true clovers”.
The white clovers (Trifolium repens L.) and red clovers (Trifolium pratense L.) are the most common around Kingston, but you can also find the more pinkish alsike clover (T. hybridum), which despite its scientific name it is not of hybrid origin. You can recognize clovers by their signature three-leaved pattern suggested by the genus name: Tri =three, folium=leaf. At first glance, they might just look like weeds, but there is a lot more going on just beneath the surface.

White clover (Trifolium repens), left, and red clover (Trifolium pratense), right, showing off their ability to grow in even the tightest of spaces.

White and red clovers, like so many North American weeds, are native to Europe; in fact, the greatest diversity of species in the genus Trifolium occurs in the Mediterranean Basin (around Anatolia and Greece) where it presumably originated (Scoppola et al 2018). Two other important centres of species’ diversity are the west coast of North America, from British Columbia south to Baja California, and the alpine and subalpine highlands of central east Africa. Clovers can grow in a variety of habitats, including meadows and prairies, open woodlands, semi-deserts, mountains, alpine peaks and urban environments. However, no matter where they are, one of the most important factors determining their success is high solar radiation; few clover species tolerate shade (Ellison et al. 2006).


True clover species have some characteristics in common and can be distinguished from other similar genera because they have petals that remain on the plant after flowering; the other genera do not. Clovers also have straight pods (the structures where the seeds are contained) that rarely stick out of the calyx; the others all do stick out. In clovers, the compound leaves can have between 3 and 7 leaflets, whereas the others always have 3, and always have their flowers in variously shaped heads. The whole floral structure in clovers is adapted to insect pollination, requiring skills to push down the keel (the two lower petals forming a boat-like structure) exposing both the male (stamens) and the female parts (pistil) of the plant. In its struggle to get the nectar or the pollen, some of the pollen sticks to the insect; when it visits another flower on a new plant the pollen is transferred. In this way, cross-pollination and the mix of genetic material occurs. Some annual species, however, can set seed by self-pollination.

White clovers (T. repens), red clovers (T. pratense), and alsike clovers (T. hybridum) are all very similar except for the colour of their flowers. You can identify Trifolium species by their stalked leaflets in threes (or fours if you are lucky!). White clover leaflets are attached to a ‘creeping’ stem which runs along the ground and only grows to about 13 cm in height.
The flowers are white or pinkish and attached to a stalk and are composed of many small flowers clustered in a dense head. Red clovers, on the other hand, have upright stems that can reach up to 60 cm tall, and the signature three leaflets typically have a white V-shaped blotch. The magenta or purple flowers are similar in shape to the white clover, found in a dense head, but do not have a stalk (Newcomb 1977). The alsike clover looks like white clovers, but the flowers tend to be pink overall and the plant grows 35-75 cm high. This species does not have a white ‘V’ on the leaves.

Human uses and consumption

Because of their superior nitrogen content, clovers are a great source of ‘green manure’ – instead of using chemical fertilizers, mulch from clovers can provide your garden or crops with the nutrients they need! (Bruning and Rozema 2013). Because clovers are also high in nutrient content, these species were sown for livestock forage by colonists and have become extensively naturalized worldwide, colonizing lawns and roadsides ever since. All parts of the plant can be edible if properly prepared, and their sprouts make a tasty addition to salads, the flowers a naturally sweet tea, and the dried leaves are said to give a vanilla-like flavour to baked goods. However, caution should always be exercised when foraging – white clovers are known to produce chemicals called cyanogenic glucosides, which release the deadly toxin cyanide. While this makes white clovers dangerous for people to forage without proper knowledge of how to prepare them, it may also make them a useful pest-control agent (Bjarnholt 2008).

Several species in the Pea family growing together in an abandoned lot: White clover (white), red clover (magenta), bird’s foot trefoil (yellow), and possibly some Alsike clovers (pink).

While herbarium specimens can provide much useful information about a plant’s history, colours often fade over time – especially in the petals – when dried. Many historical botanical collections also included beautiful illustrations of the plants pointing to important taxonomic useful traits and details such as the size and shape of the leaves, flowers, fruits, seed pods and seeds. Much like modern-day field guides, botanical illustrations can serve as a reference for identifying the species. For instance, in the illustration below shows an alsike clover, where the difference is most obvious in the colour of their flowers. You can also see more clearly than in the photos the individual flowers, the keel, the sepals, and the root.

Black Medic – Medicago lupulina

The black medic is an annual, biennial, or short-lived perennial species. The genus Medicago is also a genus of the Fabaceae family, and includes the common forage crop alfalfa, Medicago sativa. The common name ‘black medic’ is at first not an intuitive alias for Medicago lupulina. It is characterized by its small yellow flowers and leaflets in threes and is closely related to the true clovers (the Trifolium species). The name Medic is derived from an Ancient Greek word meaning ‘Median’, which was the name given to alfalfa because it was believed to have been introduced from the region of Media (which is in modern-day Iran). Today, black medic can be found throughout the world and is a common weed of lawns and waste places in Kingston, however, it is not considered to be of concern in managed agricultural systems and is not listed as a noxious weed in Canada (Weed Seeds Order, 1986).

Black medic creeping from lawn to sidewalk on York St. in Kingston, ON

Like the white and red clovers, black medic was introduced to North America during the era of colonization. It is used as fodder, especially for sheep, and it is commonly used for making honey. The bright yellow flowers attract honeybees, moths and butterflies, which help to pollinate the plant. As a member of the Fabaceae family (or the legumes) M. lupulina can also improve soil quality over time by fixing nitrogen through its helpful association with rhizobia (bacteria) instead of competing with other plants for nitrogen in the soil. It is less susceptible to the fungal disease ‘clover rot’ than the red clover, which makes it especially useful in agriculture (Turkington and Cavers, 1979). Chemicals produced by the black medic plant called saponins have shown antifungal properties, which has the potential for use in medicine against a broad spectrum of diseases (Zehavi and Polacheck, 1996).


Medicago lupulina, showing a yellow head in full flower and spirally coiled seed pods, turning black as they mature.

Black medic bears a strong resemblance to the hop clover Trifolium dubium, which is also known as the lesser trefoil. They are similar in size, and both have small yellow flowers in a dense head, and three leaflets with a long stalk. In spring and early summer, they are especially difficult to distinguish from one another. The small, black, spirally coiled pods of the black medic fruit is the easiest way to distinguish it from similar-looking plants. Additionally, the leaves of the black medic tend to be hairier and are tipped with a small bristle. The stem is also hairy, whereas the hop clover’s stem is smooth, and the leaves have no bristle (Newcomb, 1977). Here is a great chart for differentiating yellow clovers in the field! Have you found T. dubium? Share a photo with us and we will post it here!

Annie A. Boyd, one of the very few female botanists of the late 1800’s contributed this beautiful M. lupulina specimen collected in 1897 to the Fowler Herbarium. If you are in the Kingston area you can visit Lake Ontario Park, the site where she collected this specimen. You are likely to see black medic along the trails edge – you may even be looking at a distant relative of the individual that Boyd collected herself over 100 years ago!

Despite this specimen’s age, you can still make out the yellow flowers and the distinctive black coiled seed pods of this Medicago lupulina specimen housed in the Fowler Herbarium at QUBS.



  1. Bjarnholt, N., M. Laegdsmand, H. C. B. Hansen, O. H. Jacobsen, and B. L. Møller. 2008. Leaching of cyanogenic glucosides and cyanide from white clover green manure. Chemosphere 72:897–904.
  2. Bruning, B., and J. Rozema. 2013. Symbiotic nitrogen fixation in legumes: Perspectives for saline agriculture. Environmental and Experimental Botany 92:134–143.
  3. Ellison, N. W., A. Liston, J. J. Steiner, W. M. Williams, and N. L. Taylor. 2006. Molecular phylogenetics of the clover genus (Trifolium-Leguminosae). Molecular Phylogenetics and Evolution 39:688–705.
  4. Gillett, J.M., Taylor, N.L., 2001. The World of Clovers. Iowa State University
  5. Press, Ames, Iowa, USA.
  6. Newcomb, L. 1977. Newcomb’s Wildflower Guide. Little, Brown and Company. New York. pp. 36; pp. 58 – 60.
  7. Turkington, R., and P.B. Cavers. 1979. The biology of Canadian weeds. 33. Medicago lupulina L. Can. J. Plant Sci. 59: 99 – 110.
  8. Weed Seeds Order. 1986. Order determining the species of plants the seeds of which are deemed to be weed seeds. Seeds Act. S-8-SOR/86-836.
  9. Zehavi, U., and I. Polacheck. 1996. Saponins as antimycotic agents: Glycosides of medicagenic acid. In: G.R. Waller, and K. Yamasaki, editors. Saponins Used in Traditional and Modern Medicine. Advances in Experimental Medicine and Biology 404. Springer, Boston, MA.

Shepherd’s Purse – Capsella bursa-pastoris (Brassicaceae)

by Adriana Lopez-Villalobos and Amelie Mahrt-Smith

Image 1. Shepherd’s Purse, Capsella bursa-pastoris, growing between the cracks of the sidewalk on Garrett St. in Kingston, ON

Capsella bursa-pastoris may at first appear to be just another weed blending into the sea of fresh spring greenery. But take a closer look at this plant commonly known as Shepherd’s Purse, and you will notice the curious appendages from which it got its name. Its distinctive seed pods – small pouches in the shape of a heart – bear resemblance to an old-fashioned style of purse carried by shepherds in centuries past [6]. This widespread edible weed is a part of the Mustard family, Brassicaceae. This family is shared by garlic mustard (see our previous post about it), thale cress, and many common supermarket vegetables like broccoli and kale. Of the five species in the Capsella genus, C. bursa-pastoris is the only one found in North America, which makes it easier to identify this species in your community.

Image 2. Notice the large, irregularly lobed basal leaves and smaller, clasping stem leaves (left); as well, the small cluster of white flowers at the tip and the ‘purse-shaped’ seed pods emerging laterally from the stem (right).

Shepherd’s Purse is a cosmopolitan weed: it is found all over the world. Its secret weapon is its ability to grow in a wide variety of conditions. It can be found in disturbed ground or dumps, and frequently invades the cultivated soil in gardens and crops. It can grow in full sun or partial shade, dry or moist soils, and even cracks in concrete (Image 1); its hardiness makes it a good contender for urban living [3]. You can identify Shepherd’s purse by its large leaves with irregular lobes at the base of the stem, and smaller, arrow-shaped leaves that clasp the stem. In good conditions, it can reach 60-80 cm tall. Its tiny white clustered flowers have four petals each (with the 6 distinctive stamens: 2 outer short and the 4 inner long). The most identifiable feature is the heart-shaped seed pods attached to the main stem by a long stalk, which makes it distinguishable from similar plants like wild mustard (Image 2) [5]. Early in the spring, Shepherd’s Purse’s flowers begin to bloom, and they will continue to bloom until late fall. It is an annual, which means an individual plant only survives for one year, but several generations can be produced during the warmer months, and a single plant can produce up to 45,000 seeds! This is a high level of production that is facilitated, in part, by their ability to self-pollinate. Instead of waiting for an insect to come by and transfer pollen from one individual to another, the pollen simply fertilizes the flower from which it was produced (or a close neighbouring flower) [4].

Image 3. A Shepherd’s Purse plant collected in 1862, specimen is part of the Fowler Herbarium collection at QUBS. Click on thumbnail for larger image.

C. bursa-pastoris was introduced to North America by European settlers many times over. In the southwestern United States, it hitched a ride with Spanish colonizers, while further north in the U.S. and Canada, we have the British and French colonists to blame [7]. Shepherd’s Purse was once an important European medicinal herb, especially for women. Like many plants, has been overtaken by more effective modern drugs. All its parts are edible and can be used as a peppery seasoning – although we do not recommend you try this with unfamiliar plants! The leaves, which are high in vitamins and minerals, were traditionally made into a tea for the relief of pre-menstrual cramps and to reduce the risk of haemorrhaging after childbirth [1,2]. The Fowler Herbarium at the Queen’s University Biological Station has C. bursa-pastoris specimens collected in Kingston during the 1800s. This beautifully preserved Shepherd’s Purse specimen was collected in 1862 in the former township of Ramsay, Lanark County, which lies between modern-day Kingston and Ottawa. Notice the defining features of C. burasa-pastoris: the larger basal leaves, small stem leaves, heart-shaped seed pods, and clusters of tiny flowers at the tip (no longer white, but you get the idea.


  1. Aksoy, A., Dixon, J.M. and Hale, W.H. 1998. Biological flora of the British Isles. Capsella bursa-pastoris (L.) Medikus (Thlaspi bursapastoris L., Bursa bursa-pastoris (L.) Shull, Bursa pastoris (L.) Weber). Journal of Ecology 86, 171-186.
  2. Ghalandari, S., Kariman, N., Sheikhan, Z., Mojab, F., Mirzaei, M., and Shahrahmani, H. 2017. Effect of hydroalcoholic extract of Capsella bursa pastoris on early postpartum hemorrhage: A clinical trial study. J Altern Complement Med 23, 794‐799. doi:10.1089/acm.2017.0095
  3. Grieve, M. 1984. A Modern Herbal. Penguin. New York. ISBN 0-14-046-440-9
  4. iNaturalist. Shepherd’s purse. iNaturalist. https://www.inaturalist.org/guide_taxa/330084
  5. Newcomb, L. 1977. Newcomb’s Wildflower Guide (pp. 150). Little, Brown and Company. New York.
  6. 6. Reader’s Digest Field Guide to the Wild Flowers of Britain. Reader’s Digest. 1981. p. 54. ISBN 9780276002175.
  7. Neuffer, B., and Hurka, H. 1999. Colonization history and introduction dynamics of Capsella bursa-pastoris (Brassicaceae) in North America: isozymes and quantitative traits. Molecular Ecology 8, 1667-1681.

Garlic Mustard, Alliaria petiolata (Brassicaceae)

by Adriana Lopez-Villalobos and Amelie Mahrt-Smith

Image 1. Garlic mustard invading a lawn on Bagot Street, Kingston ON. Click on thumb for larger view.

Next time you are out for a walk around the neighbourhood, keep your eyes out for this weed in lawns, empty lots, and along trails. Alliaria petiolata, commonly known as garlic mustard, is in bloom through spring and early summer in Ontario. This widely distributed herb is a member of the Brassicaceae (Mustard) family alongside many well-known, if not well-liked cruciferous vegetables: broccoli, kale, brussels sprouts, turnip, horseradish, and wasabi, to name a few [3]. Garlic mustard gets its name from the garlic smell released by the leaves when crushed; the leaves, as well as the flowers and seeds, are edible and add a mild garlic or mustard flavour to dishes.  Make sure to you ask your neighbours if they have used herbicides on their lawn before you try adding garlic mustard leaves to your salad or pesto!

Image 2. Close-up of garlic mustard, Alliaria petiolata, showing its four-petaled white flowers and saw-toothed leaves. Click on thumb for larger view.

Mature garlic mustard plants are easy to identify. The heart-shaped leaves have saw-toothed edges, prominent veins, and long stalks connecting them to the main stem. Leaves  are unpaired and  alternate in their position on the stem. Its height varies, but in rich soil can reach up to 1 metre tall. The flowers are somewhat inconspicuous: small and white, each with four sepals and petals (both free), and clustered at the tips. As it is typical of the mustard family, the flowers have six stamens (male part) with the two outer stamens shorter than the four inner stamens. These flowers only develop in the plant’s second (and final) year of life (Images 1 and 2). In its first year of growth, the leaves are more rounded and can look like some other common Ontario herbs like violets or wild ginger [4]. Your other senses will come in handy here – you can tell young garlic mustard apart from the rest because its leaves will still have the distinctive garlic smell when crushed.

Despite its abundance in North America today, garlic mustard did not exist here until around the 1800s, when it was purportedly  introduced by European settlers who cultivated it for food and medicine. It is a good source of vitamin A and C and was used as an antiseptic to treat ulcers and relieve itching caused by insect bites and stings [2], so it makes sense they would have wanted this useful plant with them in this strange new world.  However, since its introduction to North America,  A.  petiolata  has spread vigorously and crowded out some of the native flora, preferentially invading areas of moist soils and shade. Dr.  Rob Colautt i  of the Queen’s University Biology Department has been investigating the effects of this species on the soil microbial communities as a possible explanation for its rapid invasion [https://www.ecoevogeno.org/research.html].  His research has found that  A.  petiola  does alter some nutrient-cycling bacteria in the soil [4]. We are excited to see the results of his ongoing work!

Image 3. An Alliaria petiolata individual collected in 1886 in Sweden. Click on thumb for larger view.

Herbarium specimens can tell us much about the history of garlic mustard. This specimen from the Fowler Herbarium (Image 3) was collected in Sweden in 1886; back then, the scientific name for this plant was Sisymbrium alliaria (now a taxonomic synonym). As more species and molecular tools are used in taxonomic studies, the names of species sometimes change. Taxonomy is constantly being revised and families, genera and species are continually being re-assigned as a result. Herbaria must be periodically updated with the most recent information – here, we can see that the genus and species was revised by Assistant Curator A.E, Garwood in 1980, and again in 1990 to what is currently the accepted name of the species: Alliaria petiolata (M. Bieberstein) Cavara & Grande. Our efforts to digitize the specimens housed by the Fowler Herbarium have also given us a chance to revise any outdated information in the collection.


  1. Colautti, R.I. Research.  Colautti Lab.  https://www.ecoevogeno.org/research.html
  2. Grieve, M. 1984. A Modern Herbal. Penguin. New York. ISBN 0-14-046-440-9
  3. Koch, M., Al-Shehbaz, I.A., and Mummenhoff, K. 2003. Molecular systematics, evolution, and population biology in the mustard family (Brassicaceae). Annals of the Missouri Botanical Garden 90, 151 – 171.
  4. Lavoie, K., Antunes, P.M., and Colautti, R.I. Effects of Alliaria petiolata invasion on soil microbial community structure inferred from bacterial 16S and fungal ITS metabarcodes. (in prep.)
  5. Newcomb, L. 1977. Newcomb’s Wildflower Guide. Little, Brown and Company. New York. pp. 138.