Stephen J. Darbyshire

The Biology of Invasive Alien Plants in Canada. 2. Cynanchum rossicum (Kleopow) Borhidi [= Vincetoxicum rossicum (Kleopow) Barbar.] and Cynanchum louiseae (L.) Kartesz & Gandhi [= Vincetoxicum nigrum (L.) Moench]

Cynanchum rossicum (dog-strangling vine) and C. louiseae (black dog-strangling vine) are introduced, perennial herbs or small twining vines in the Milkweed family (Asclepiadaceae). Generic placement of these two species has been problematic, but are here treated as members of Cynanchum subgenus Vincetoxicum. The species occur primarily in natural upland areas, including understories of woodlands, pastures, old fields, shores, flood plains and ruderal areas of southern Ontario and Quebec and the northeastern United States. Ecosystems on well-drained, stony soils are often densely colonized, but both species can tolerate a wide moisture regime. Plants establish in full sun or under forest canopies and may form monospecific stands in all light conditions. They often form dense colonies which smother other vegetation and reduce invertebrate and vertebrate biodiversity. Reproduction is by polyembryonic, wind-dispersed seeds. Effective control is primarily by herbicides, since mechanical control is difficult an...

The Biology of Invasive Alien Plants in Canada. 4. Heracleum mantegazzianum Sommier & Levier

Heracleum mantegazzianum (giant hogweed) is an invasive alien plant of management concern in southern Canada where it has escaped from horticulture and established and spread in natural, ruderal, and agricultural ecosystems. It poses a threat to natural ecosystems and human health, and is also a weed in agricultural and urban areas. It is a member of the Carrot family (Apiaceae) and is closely related to the native species Heracleum maximum Bartram (cow-parsnip). It is a monocarpic perennial, which generally flowers in its 3rd or 4th year. Large size, leaf shape, dark reddish pigments in patches on stems and petioles, and fruit characteristics readily distinguish H. mantegazzianum from other plants in Canada. It is increasingly common in riparian areas, floodplains, and forest edges in or near urban areas in southwestern British Columbia and southern Ontario. Based on herbarium specimens, H. mantegazzianum was first recorded in Ontario in 1949, British Columbia in 1964, Nova Scotia in 1980, Quebec in 1990...

The biology of invasive alien plants in Canada. 7. Cabomba caroliniana A. Gray

The freshwater aquatic plant Cabomba caroliniana, or fanwort, was recently reported in a lake northeast of Peterborough, Ontario, where it has successfully established and survived winter conditions since at least 1991. This is the first documented occurrence of fanwort becoming naturalized in Canada. Fanwort is a popular aquarium plant that is native to South America and possibly the southeastern United States and has been introduced in several Asian, Pacific and European countries through the discarding or deliberate planting of aquarium plants in natural waterways. It is particularly invasive in China, Japan and Australia, and in parts of the United States, where its range is spreading. Fanwort grows rapidly and forms dense stands that clog waterways, impeding flow, obstructing navigation, altering fish habitat and excluding other vegetation. It does not produce mature seed in the northern parts of its North American range, but can multiply clonally and spread quickly by stem fragmentation. It produces...

The Biology of Canadian Weeds. 111. Anthriscus sylvestris (L.) Hoffm

Wild chervil, Anthriscus sylvestris (L.) Hoffm. (Apiaceae), is a weed of perennial crops, old fields, disturbed areas and roadsides. Introduced from Eurasia, it is widely naturalized in eastern Canada from Newfoundland to Ontario and at two sites in British Columbia. It is a monocarpic short-lived perennial, reproducing by seed and budding from the root crown. Dense populations achieved through vegetative reproduction can exclude most other vegetation. The rust, Puccinia pimpinellae subsp. pimpinellae, was detected on a population of wild chervil from Quebec. Key words: Wild chervil, Anthriscus sylvestris, weed biology

The Biology of Canadian Weeds. 141. Setaria faberi Herrm.

Setaria faberi, commonly known as giant foxtail, is an annual graminaceous weed that is native to eastern China, has colonized eastern North America and is expanding its range westward. This species is primarily self-pollinated and the only mechanism of reproduction is by seed. Adult plants may reach 2 m in height and produce over 2000 seeds per panicle. Seeds may possess non-deep physiological dormancy when freshly produced, and can form small persistent seed banks. If not controlled, S. faberi populations can cause severe yield reductions in corn and soybean crops. Several herbicides are available to provide chemical control; however, resistance to some modes of action, (ALS, ACCase, and Photosystem II) have been identified in Canada and the United States. Leaves and seeds of this species provide a food source to several species of mammals, birds, and insects. Key words: Setaria faberi, giant foxtail, growth, development, seed germination, diseases, herbicide

The Biology of Canadian weeds. 144. Pastinaca sativa L.

The parsnip, Pastinaca sativa, was introduced to North America shortly after European settlement as an important root-crop. It subsequently escaped cultivation and naturalized as a less palatable “wild” form. Cultivation of parsnip has diminished in Canada to the point where it is now only a minor crop, but the wild form has increased as a troublesome weed, particularly in eastern regions. Wild parsnip is most prevalent in eastern Canada and the northeastern United States, but occurs across the continent except in the far north and extreme southeast. As a monocarpic biennial with a large tap root, it reproduces entirely by seed. A wide variety of habitats and soil types are tolerated. It is considered a noxious weed because of its toxic properties (primarily photo-activated dermatitis) to both humans and livestock. It invades disturbed sites, rights-of-way, pastures, perennial crops, and reduced-tillage fields where it effectively out-competes shorter vegetation. In arable fields, wild parsnip is normally...

The Biology of Canadian Weeds. 143. Apocynum cannabinum L.

Hemp dogbane, Apocynum cannabinum (Apocynaceae), is a perennial herb with white to greenish flowers in terminal clusters that produces pencil-like pods 12-20 cm long. A highly variable plant, A. cannabinum may be distinguished from spreading dogbane (Apocynum androsaemifolium) by its shorter corolla (2-6 mm compared with 5-10 mm), erect greenish-white petals (compared with recurved or spreading pinkish petals), seeds more than 3 mm long (compared with seeds less than 3 mm), and more erect leaves (compared with spreading or drooping leaves), although frequent hybridization between the two species obscures the identity of some individuals. Hemp dogbane is native to the United States and southern Canada, but most abundant in the upper Mississippi River Valley and east to the Atlantic coast. It has been increasing in other areas, and becoming more of a problem where conservation tillage is adopted. It infests crops such as corn (Zea mays), soybeans (Glycine max), wheat (Triticum aestivum), sorghum (Sorghum bi...

The biology of invasive alien plants in Canada. 10. Nymphoides peltata (S. G. Gmel.) Kuntze.

The freshwater aquatic species Nymphoides peltata has been introduced to Canada as an ornamental plant and has been found at sites in Newfoundland, Nova Scotia, Quebec, Ontario and British Columbia. It is currently available through the aquatic nursery trade in Canada and the United States. It may be considered as adventive in Canada since populations readily expand beyond the site of planting, but there is no evidence as yet that it is fully naturalized. In the United States it has naturalized in still or slow-moving waters at widely scattered locations where it replaces native plant communities, changes ecological processes and interferes with human navigation and recreational activities. The short rhizomes over-winter under Canadian conditions, even when complete water drainage results in freezing of the substratum. In its native range, the species has two floral morphs (i.e., is distylous) with a weak incompatibility system, but North American populations usually consist of a single flower morph. A po...

Impact of post-anthesis glyphosate on woolly cupgrass seed production, seed weight and seed viability

Nurse, R. E., Darbyshire, S. J. and Simard, M.-J. 2015. Impact of post-anthesis glyphosate on woolly cupgrass seed production, seed weight and seed viability. Can. J. Plant Sci. 95: 1193-1197. Herbicides are generally applied at early stages of crop and weed growth to protect crop yield. Few studies have evaluated the effect of late (post-anthesis) applications of glyphosate as a management option to limit the seed production of weed escapes, such as woolly cupgrass (Eriochloa villosa). We propagated woolly cupgrass under greenhouse conditions and then applied three glyphosate treatments post-anthesis including: (1) an untreated control; (2) 900 g a.e. ha-1; and (3) 1800 g a.e. ha-1. Terminal inflorescences were collected 21 d after glyphosate application, and seed production, seed weight and embryo viability were assessed. Post-anthesis glyphosate applications did not influence seed production, but reduced seed weight and viability by 50 and 96%, respectively. Therefore, glyphosate applied just before the woolly cupgrass inflorescence begins to emerge from the leaf sheath (as late as the R1 stage in soybeans) is an effective strategy to manage woolly cupgrass reproduction and stop viable seeds from entering the soil seed bank or other dispersal pathways.

35. Mosquito Ferns (Azolla species) – tiny ‘super plants’

Biodiversity is threatened by humankind’s continuing usurpation of our planet’s physical space and resources, and the associated damage to the landscape and atmosphere. Food production is widely acknowledged to be the most important human activity that needs to be addressed in order to mitigate the current biodiversity and environmental crises. In this contribution we feature obscure plants called Mosquito Ferns, whose minute size belies their incredible potential. Nicknamed ‘super plants’, these can not only produce food more rapidly than virtually any other life form, but do so in biodiversity-friendly ways that minimise use of space and energy resources. Mosquito Ferns are poised to become leading players in the search for sustainable relationships with the natural world.