Plants Burdocks in Saskatchewan

PLANTS BURDOCKS IN SASKATCHEWAN VERNON L. HARMS, #212-115 Keevil Crescent, Saskatoon, SK S7N 4P2 Burdocks (Arctium spp.) are tall, effective seed-dispersal by attaching to coarse, biennial, exotic weeds, originally animal fur and our clothes. from Eurasia, that already by the mid- 1600s had been unwittingly imported Four burdock species are known in into North America by early English and North America, one of which, Lesser or French colonists.1 These conspicuous Common Burdock (Arctium minus), is plants, mostly exceeding a metre in spread across the continent in temperate height, tend to grow in various relatively regions, having become most abundant moist, human-disturbed sites where in eastern North America, less frequent they often form large dense patches. on the Great Plains, and relatively uncommon in drier parts of the Burdocks are members of the Thistle southwestern and western United States. Tribe (Cynareae), of the Sunflower Historically, burdocks have not been Family (Asteraceae), and like all considered particularly frequent in composites have flowers borne in heads Saskatchewan. They do not, however, surrounded by bracts forming well- represent recent introductions into the defined involucres. The leaves are large province since a Regina collection of and more-or-less woolly underneath. As Lesser Burdock made by C.N. Willing biennials, the first-season plants consist dates back to 1908, a Maple Creek of a deep taproot bearing large, more- record to 1930, a Big River one to 1938, or-less triangular, basal leaves, mostly and six other scattered records to the 14 to V2 metre long. These leaves tend 1940s and 1950s. While in the past they to remind one of Arrow-leaved Colt’s- apparently were rather infrequent weeds foot (Petasites sagittatus (Pursh) Gray), in Saskatchewan, burdocks may now be but they are more irregular in shape with increasing in frequency and numbers. many clustered from a taproot. The stout, tall, much-branched stems appear The distributional information in this in the second year and bear alternately article is based on numbers and locations arranged leaves and numerous flower- of burdock collections deposited in the heads. As all thistles and their relatives, W.P. Fraser Herbarium in Saskatoon, the but unlike many other composites such G.F. Ledingham Herbarium in Regina, as asters, daisies and sunflowers, and the Swift Current Agriculture Canada burdock heads lack rays. The tubular Research Centre. But how well florets, with purple to pink (rarely white) herbarium collections reflect the actual corollas, are surrounded by numerous, distributions and abundance of the overlapping, thickish involucral-bracts species is questionable. At best, they can tapered upwards to sharp hooked tips only represent a rough sampling of the (at least outer ones) that form large species. globe-shaped, spiny involucres around the heads (Figure 1). In late-flowering Three burdock species are documented and fruit stages, the heads look like as occurring in Saskatchewan. These spiny burs, and are well adapted for are: Lesser or Common Burdock 92 Blue Jay 59(2). June 2001 Figure 1. Morphology of Saskatchewan Burdock Species. Adapted from Moore & Frankton (1974) 93 (Arctium minus Bernh.), Woolly or to 1.5 m tall..A. tomentosum. Cotton Burdock (Arctium tomentosum 2b. Involucres smooth, not hairy; corolla- P.Mill.), and Great Burdock (Arctium tips not glandular; petioles solid; heads lappa L.). The fourth North American 3.0-4.5 cm wide; middle and inner species, Woodland Burdock (Arctium involucral bracts nearly equal and nemorosum Lej. & Court., now referred surpassing corollas; plants often larger, to A. vulgare (Hill) Evans), has to 3 m tall.. A. lappa. sometimes been listed for the province, but this appears erroneous, with The Woodland Burdock would differ Saskatchewan specimens once from the above three species in having identified as this species now revised racemosely arranged heads, and leaf- to A. tomentosum. All known shape and leaf-stalks like A. minus, Saskatchewan sites of burdocks are usually ± arachnoid involucres like A. located in the agricultural region, south tomentosum, larger heads and inner of latitude 53° (see Figure 2), except for involucral bracts exceeding corollas like a record of Lesser Burdock from Big A. lappa, and non-glandular corollas River, and an unverified record of Great unlike A. tomentosum. Burdock from north of Nipawin. The following key may be used to distinguish Lesser or Common Burdock, Arctium our Saskatchewan burdock species: minus Based on records in provincial Identification Key to Arctium herbaria, Lesser Burdock is the most (Burdock) Species in Saskatchewan common burdock species in la. Heads (1.5-) 2-2.5 cm broad, Saskatchewan, as in North America. racemose or racemosely clustered, with The herbarium survey revealed a total at least the middle and upper ones of 39 collections of this species, from sessile or short-stalked; larger leaf- apparently 28 different sites and 24 blades tapering at apex to usually ± general localities in the province. While broadly acute tips; leaf-stalks hollow and records are scattered from the southern only slightly angled; corolla limbs not border, north to Big River and Armit (east glandular; involucres strongly of Hudson Bay near the Manitoba contracted at top, the middle and inner border), this species appears most involucral bracts successively larger, the frequently encountered in the more inner ones shorter than corollas; plants southern regions of the province south to 1.5 m tall.. A. minus. of latitude 51 ° N. (Figure 2). The earliest 1 b. Heads ± corymbosely arranged with collections of Lesser Burdock in at least the lower on long stalks; larger Saskatchewan are from Regina (1908), leaf-blades rounded at apex; leaf-stalks Maple Creek (1930, 1936), Big River strongly angled, either solid or hollow; (1938), Carlyle (1941), Armit (1948), corolla limbs glandular or not; involucres Stockholm (1948), and Hidden Valley more cup-like, less contracted at top. - (on Qu’Appelle River north of Regina) .(to 2). (1949). Additional collection records are 2a. Involucres distinctly arachnoid- spread over the remaining decades of tomentose (spiderwebby to cottony); the 20th century (Figure 3). The most corolla limbs glandular and abruptly frequently listed habitats for Lesser dilated; petioles hollow; heads 2.0-2.5 Burdock in Saskatchewan were (-3) cm broad; middle and inner disturbed understories of stream-edge involucral bracts successively larger, the woods, roadside ditches, field edges inner ones longer than, subequal to, or and waste areas. Other habitats listed mostly shorter than the corollas; plants included open stream and slough edges, 94 Blue Jay I 1 Figure 2. Saskatchewan Distribution of Burdock Species 96 Blue Jay farmyards, corrals, and garden margins. specimen labels gave no indication of Unfortunately most specimen labels gave local abundance, of those that did, half no indication of local abundance, but of stated the plants to be common or about a dozen that did, two-thirds stated occurring in large patches, while the that the plants were common or locally other half indicated the plants to be frequent and one-third said they were locally uncommon or only occasional. few, several or uncommon. With regard Early anthesis stages were seen on to the flowering and fruiting phenology specimens collected from early July to of Lesser Burdock, early anthesis (i.e. early August, and full anthesis on those flower bud and young flower) stages were from mid-July to early October. seen on collections from late June to late July. Full anthesis (i.e. mature flowers) Great Burdock, A. lappa stages could be seen on late July to mid- Great Burdock is the rarest species October collections. Except for one mid- of burdock in Saskatchewan, with only October collection, fruits were only seen one confirmed record in the province on previous-year’s dried stalks of several and two unconfirmed ones. A verified spring - early summer collections with 1981 collection was from a “field-edge current-year’s leaves. Such specimens wasteland” near Biggar. An unverified raise a question - are these burdocks 1974 collection is reported from 5 km strictly biennial or possibly somewhat east of Touchwood, and an unconfirmed perennial at this latitude? Actual 1975 record exists from Garrick (about connections of the old fruiting stalks to 27 km NW of Nipawin). These two are the roots bearing new leaves could not indicated by circled question marks on be ascertained from the herbarium the right hand map in Figure 2. The specimens seen. single verified collection of Great Burdock in Saskatchewan was in Woolly or Cotton Burdock, A. flowering stage in mid-August. tomentosum The second most frequently Discussion encountered burdock species in The quite late summer flowering Saskatchewan is Woolly Burdock, with periods and apparently late fruit a total of 19 collections, from apparently production, occurring well after our first 17 different sites and 15 general frosts, seem interesting phenological localities in the province. While records features of burdocks in Saskatchewan. are scattered over the southern third of Could autumn frosts possibly hamper the province, this appears to be the most fruit development and represent a frequently encountered burdock species limiting factor preventing burdocks from north of latitude 51° N. (Figure 2). The becoming more abundant here? oldest records of Cotton Burdock in Saskatchewan are from Rosthern A review of herbarium collections (1936), southwest of Swift Current gives us a glimpse of the localities and (1956), and Kamsack (1959). All other dates of burdocks in Saskatchewan, and collections are dated in the 1980’s and provides some historical perspective on 1990’s. The most frequent habitats listed their occurrences. It is conjectural to for Saskatchewan collections of Woolly what extent the numbers, dates and Burdock were roadside ditches, locations of herbarium collections can disturbed wooded stream margins, field be relied upon to accurately reflect the edges and waste areas.

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