| BEN |
| BOTANICAL ELECTRONIC NEWS |
|---|
| ISSN 1188-603X |
| No. 314 September 23, 2003 | aceska@victoria.tc.ca | Victoria, B.C. |
|---|
Giant hogweed or giant cow-parsnip, Heracleum mantegazzianum Sommier & Levier (Apiaceae), is a conspicuous and potentially troublesome exotic plant species which is in its initial stages of invasion in southwest British Columbia. Because management is most effective on small populations during population expansion, the purpose of this article is to raise awareness and improve management, particularly focusing on eradication, early in the invasion process in British Columbia. A detailed description of its current distribution in British Columbia is included.
Heracleum mantegazzianum is a member of the carrot family (Apiacae) whose native range is the Caucasus Mountains in southwest Asia (Tiley et al. 1996). It is closely related to a widespread native species, Heracleum maximum Bartram (cow-parsnip; previously known as Heracleum lanatum Michaux), which is found in wet meadows, roadsides, and moist forests throughout British Columbia. Heracleum mantegazzianum has been introduced to western Europe, Britain, Scandinavia, eastern North America, and the Pacific Northwest purposefully or by accidental human transport (Morton 1975; Pyšek 1991; Tiley et al. 1996; Darbyshire & Morton 2003; Booy, 2003). It is designated as a noxious weed in Washington, Oregon, Florida, and North Carolina (USDA, 2003).
Heracleum mantegazzianum is generally distinguished from H. maximum by its larger size; where flowering plants of H. maximum seldom reach over 2.0 m in height, H. mantegazzianum_ is often 2.5 to 4 m in height with lower leaves in a basal rosette between 1.5 to 2.0 m in total breadth. It is recognized by the Guinness Book of Records as the world's largest weed (listed at 3.65 m tall) (Guinness World Records, 2003). The stem can be >10 cm in diameter although 3-8 cm is more common. Another identifying characteristic is diffuse or patchy purplish-red pigmentation with raised bumps or nodules on the stem, whereas H. maximum may have some purplish spots but it is generally light green in colour with diffuse hairs. The inflorescence of H. mantegazzianum forms a broad (30-50 cm) flat-topped umbel composed of many small white florets. Seed production is heavy and one plant may produce between 1,500-100,000 seeds (mericarps) per plant (Tiley et al. 1996). The fruit of H. mantegazzianum tends to be larger than that of H. maximum (about 1-1.5 cm long compared to 0.8-1.2 cm) with different resin canal structure (Darbyshire and Morton 2003). Dispersal is either by water movement along streams, ditches, and urban storm drainage systems, or by human activity. Some fruits or seed heads are picked for decorative uses, garden planting and culinary purposes (e.g., golpar spice), however, transport of soil and seed from infested areas by machinery is likely a more important means of dispersal.
There are two primary reasons why Heracleum mantegazzianum is considered an invasive species of management concern in British Columbia. First, it can exclude native plant species through direct competition for light or other physical resources in open habitats (e.g., forest edges, meadows, stream margins) (Tiley et al. 1996). Dense patches along forest edges that were subjectively evaluated in the City of North Vancouver had very low plant species richness, particularly of native species. Heracleum mantegazzianum may also reduce streambank stability by reducing native shrub or forb cover during the winter flood period. It can also establish in shaded forest such as stream ravines, although its growth and flowering is reduced and it is not considered a strong competitor in these environments (Tiley et al. 1996). Second, H. mantegazzianum produces light-activated chemicals (furanocoumarins) in its leaves, roots, stems, flowers, and seeds which can cause minor to severe contact dermatitis in combination with exposure to sunlight (Camm et al. 1976; Towers 1980). Furanocoumarin-induced dermatitis typically consists of blisters that form within 48 hours and become pigmented (blackened or purplish) scars that can last as long as 6 years (Tiley et al. 1996). Longterm sensitivity to sunlight may follow. The highest concentrations of furanocoumarins are present in leaves and roots during the early part of the growing season (Knudsen 1983). Heracleum maximum and other members of the carrot family also contain furanocoumarins (Nielsen 1971).
Based on current distribution patterns, Heracleum mantegazzianum appears to have been originally introduced at two localities in southwest British Columbia: French Creek near Parksville on eastern Vancouver Island; and the City of North Vancouver on Vancouver's North Shore.
Heracleum mantegazzianum was first recorded in riparian areas along French Creek in 1964 (Dawe and White, 1979) and the largest populations on Vancouver Island are still found in the surrounding area. Dawe and White (1979) speculated that it had been introduced by 1944 although the exact site and source are uncertain. Beyond the French Creek area, Ron Wall and colleagues have documented an expanding list of occurrences on southeastern Vancouver Island including the Victoria area (garden on Helmcken Rd.; Weir's Beach, Metchosin), Saltair (garden on Chemainus Rd.), Gabriola Island (Drumbeg Park), Nanaimo (gardens near Quennel Lake and Cat Stream; ditch along College Drive; Island Highway near airport), Nanoose Bay (gardens on Seahaven and Ashcroft roads; Island Highway near Nanoose Creek), Parksville (Heath Ave. near Englishman River estuary; Aquila Park), Errington (Island Highway near Englishman River; Leffler Rd.), Qualicum Beach (beach near Old Island Highway; Seacrest Place), Qualicum Bay (Dunsmuir Rd.; garden on Old Island Highway), and Denman Island (private garden). Also, there have been recent unconfirmed reports in a wholesale nursery near Cobble Hill, along the E&N Railway line in Nanaimo, on Shooting Star Place in Nanoose Bay, in a private woodlot near the Englishman River in Errington, in the Eaglecrest area of Qualicum Beach, along Whiskey Creek near Coombs and in Courtenay.
In the Lower Fraser Valley, the earliest record based on a confirmed specimen is in Mahon Park in the City of North Vancouver from 1974 (UBC Herbarium Acc. 156773). This is believed to be the epicenter of Heracleum mantegazzianum invasion in the Lower Fraser Valley as the largest populations are currently located along Wagg Creek near Mahon Park (19th St. and Jones Ave.). Recent assessment and mapping for the City of North Vancouver's Engineering, Parks and Environment Department found smaller populations along roadsides and streams throughout the City of North Vancouver with larger populations on Mosquito Creek near Upper Levels Highway (and downstream); 3rd St. west of Lowlevel Road; and in the Tempe Heights area east o? Lynn Valley. The assessment showed that H. mantegazzianum was recorded at more than 100 sites within the City of North Vancouver ranging from single plants along roadsides and streams to large patches greater than 1000 square meters. The total estimated population size in the City of North Vancouver was 7200 square meters.
Heracleum mantegazzianum is also prevalent in adjacent areas of the District of North Vancouver including the lower Seymour River and roadsides near the Ironworkers Memorial Bridge and upper Wagg Creek (St. Andrews St. and Queens Ave.) and the central portion of the Mosquito Creek watershed. It is less common east of the Seymour River but has recently been observed in Deep Cove (Parkside Creek), Dollarton Highway (Burrard Inlet Indian Reserve #3), and near Riverside Drive and Mt. Seymour Parkway. The District of West Vancouver Parks Department has been actively managing H. mantegazzianum in parks for several years. Their mapping indicates it is found primarily in riparian areas in the Brothers Creek watershed (Brothers and Hadden Creeks and adjacent areas of the eastern British Properties), lower Capilano River, Vinson Creek, Marr Creek, and Westmount Creek. It has also been recorded in residential areas northwest of Lighthouse Park, in Horseshoe Bay (Wellington Ave. area), and along the roadside of Marine Drive and Sunset Avenue west of Oxley Street.
Giant hogweed is less common in other areas of the Lower Mainland. In the City of Vancouver, small populations have been observed in Vanier Park, Queen Elizabeth Park (33rd Ave. area), Stanley Park (Lions Gate Bridge area), UBC Campus (Biology courtyard), 6th Avenue (east of Alder St.), Strathcona Community Garden (orchard area), and beneath the Burrard Street Bridge. Frank Lomer has also recorded populations on the south side of Sea Island in Richmond (shore of the Fraser River and east from Oak Street bridge), along the lower Brunette River on the Burnaby / New Westminster border, in a ravine north of 100 Ave. in Surrey; north of the Roberts Bank causeway in Delta, and in south Burnaby and Coquitlam.
Control or eradication of Heracleum mantegazzianum is labour intensive and requires long term management. Recommended control methods include cutting or mowing above ground parts, digging, and herbicide application (Tiley and Philp 1994, Dodd et al. 1994, Tiley et al. 1996). Application (spraying, stem injection, wiping) of glyphosate (Roundup) in April and May before plants are 1 m tall followed by a second application later in the season is the most universally recommended control method (Tiley and Philp 1994, R. Cranston, pers. comm.). Deep tilling or severing the taproot 5 to 15 cm below the surface of the ground may be successful for small populations. Observations indicate that crushing or twisting the stem or leaf rosette during the early part of the growing season may reduce flowering, but is not effective for eradication or long term control. Seed longevity is greater than 7 years (Tiley et al. 1996) and ongoing monitoring is required, with possible repeated treatments, to prevent reestablishment. There are no applicable biological control methods although research is currently underway to identify potential fungal or insect pathogens (Ravn 2003). Sheep grazing has been used to control dense patches of H. mantegazzianum successfully (Andersen 1994) but is impractical in urban or riparian areas in British Columbia. Because H. mantegazzianum requires 2 to 4 growing seasons before flowering, eradication focusing on small, young stands is most successful. This typically requires training of both parks maintenance staff and volunteer groups to recognize and safely remove nonflowering plants. Gloves, safety goggles, and protective clothing are needed for safe handling. Stems and leaves can be left on site or composted if there is no risk of human contact. Seed heads should be disposed of separately by burning or other methods that p?events dispersal of seeds to other areas.
Invasive plant species management is generally most effective when small, initial populations can be eradicated or controlled to prevent further population expansion. Indeed, invasion ecology theory recommends that control efforts focus on small populations on the margin of range expansion as the most effective method for slowing or preventing further invasion (Moody and Mack 1988). This requires an "early-warning" system that educates observers and managers to recognize invasive species before they become widespread and abundant, and resources to rapidly eradicate or control the invading species. Too often, invasive species management focuses on activities directed at organisms that are already widespread and abundant. In the case of Heracleum mantegazzianum, resource managers have an opportunity to learn from the invasion patterns in other jurisdictions and implement municipal or provincial management strategies focusing on eradication and control of dispersal in British Columbia. Despite the large number of localities described above, many of the populations consist of small numbers of plants that could be easily eradicated. Success of an eradication program in British Columbia will depend on four key aspects:
To report new occurrences of Heracleum mantegazzianum in British Columbia, please provide specific locality data (street names, map or GPS coordinates, or a detailed site description) and the size of the population (number of plants or patch size in square meters) to Nick Page at napage@interchange.ubc.ca or Ron Wall at rrwall@shaw.ca.
A number of people kindly provided distribution records or other information for this article: Rob Adams, Richard Boase, Wade Calder, Adolf Ceska, Carol Cornish, Roy Cranston, Stephen Darbyshire, Neil Dawe, Garry Fletcher, Matt Henderson, Michael Hunter, Rose and Brian Klinkenberg, Frank Lomer, Dave Polster, Adriane Pollard, Sean Rathlef, Bob Reed, Hans Roemer and Rob Walker.
Invading plant species, such as the Centaurea (Asteraceae), establish monocultures in novel habitats by displacing the indigenous plant communities. It is thought that the absence of "natural enemies" and/or the release of phytotoxins from the invading plants by allelopathy promote this process. Previous work has shown that the European spotted knapweed (Centaurea maculosa Lam.) releases racemic catechin; the phytotoxin (-)-catechin, and the antimicrobial (+)-catechin. Invasive (-)-catechin levels in North American soil were found to be more than double those found in the natural habitats of C. maculosa. In the September 5 Science, Harsh, Bais and colleagues at Colorado State University show that (-)-catechin inhibits growth of a number of nature North American plants by altering gene expression, resulting in extensive root death (Science, 301:1377-1380, September 5, 2003).
Bais et al. used an integrated approach to establish the characteristics of (-)-catechin-mediated inhibition of plant growth. They observed that when field soil was supplemented with "invasive" levels of (-)-catechin, the germination and growth of two native grasses were dramatically reduced compared with more resistant European grasses given the same treatment. Examination of Arabidopsis thaliana (L.) Heynhold and Centaurea diffusa Lam.-a close relative of C. maculosa susceptible to (-)-catechin-at the cellular level revealed a wave of cell death, starting at the root tip that proceeded through the central elongation zone toward the stele. (-)-Catechin treatment initiated a rapid reactive oxygen species wave, similar to that observed for root cell death, but proceeding cell death by 5 to 10 minutes. ?his increase in reactive oxygen species induced Ca2+-dependent triggering of cell death. Gene expression analysis of Arabidopis thaliana showed that 10 genes were upregulated 10 minutes after treatment, with 956 genes being upregulated 50 minutes later. Many of the 956 gene products are linked to oxidative stress and the phenylpropanoid and terpenoid pathways. At 12 hours, many of these genes were repressed, possibly as a result of the onset of cell death.
"The case we have presented here for allelopathy in Centaurea maculosa challenges the conventional ecological perspective that a species' invasiveness is mainly due to enhanced resource competition after escape from natural enemies and highlights the role for the biochemical potential of the plant as an important determinant of invasive success," conclude the authors. Links for this article:
This is a hefty volume, and one very close to my heart. In total, 843 species that belong to 27 genera are treated in this volume. This is quite an achievement on in its own right, as the previous attempt of the North American Flora took over 30 (?) years to compile a monograph of this family, one which is now +/- obsolete.
A large collective of 31 authors participated in the writing of this recent volume. Most of the larger genera were coauthored by many authors; the exceptions are Rhynchospora (68 sp.), Fimbristylis (17 sp.), where Robert Kral is an undisputed king, and Schoenoplectus (17 sp.) written by S. Galen Smith. Editors did a very good job in compiling this volume and assuring the overall consistency of the work.
This is the best you can get on the sedge family (Cyperaceae) and the sedges proper (the genus Carex) in North America today. The new treatment of members of the tribe Scirpeae is especially important for the Pacific Northwest: for instance, the treatment of the genus Eleocharis substantially increased the number of species known in British Columbia (17 sp. in FNA vs. 10 sp. in The Illustrated Flora of British Columbia).
The genus Carex, on the other hand, suffered by having been written by too many individual authors; the species concept varies throughout this genus, excessive lumping in the section Acutae (now called Phycocystis), whereas other sections tended towards more splitting. The problem with Carex in North America is that the first really authoritative treatment of this genus was written by Kenneth K. Mackenzie, who was a lawyer. Consequently, you feel that you are breaking the law, if you ?on’t follow his classical treatment. The authors tried not to break the law and they followed Mackenzie's sectional divisions, even although they noted that "Mackenzie never explained his arrangement.". They abandoned the original Kuekenthal's division in the subgenera, primarily because Kuekenthal's subgenus Primocarex is obviously an artificial, hardly defensible category. (Wasn't it Raymond who wrote that if Primocarex had not existed, it would have had to be invented?) Yet, Kuekenthal's system would have been easier to follow. Fine, the authors did not accept subgenera, but did follow Mackenzie's sections and their arrangement "is a modified version of K.K. Mackenzie's system; the section largely follows his delimitation..." They in turn accepted Dumortier's sectional names, which pre- dated many traditional sectional names. The result is that many new sectional names sound unfamiliar to older botanists.
A serious failing of this volume are the omissions in the synonymy. Lists of synonyms are short and in some instances don’t even include names discussed in treatments of particular species. You won’t find the name "Carex angustior" in this volume at all. This will give me some hope that this species was omitted by mistake, rather than synonymized with another, possibly unrelated taxon.
The distribution maps are reduced to the map of US states and Canada provinces where the occurrence of each species is indicated by one dot for the whole province or state. It is a pity that the distributional maps do not provide more detail.
The majority of the authors are from east of the Continental Divide and some obvious errors resulted from this skewed distribution of the authorship. Rhynchospora capillaris, Eriophorum virginicum (adventive), Carex torreyi, etc. occur in British Columbia. You can blame regional reviewers, including me, for some of these omissions, but is some cases (e.g., Carex torreyi) there were specimens from British Columbia in major Canadian herbaria in Ottawa that should have been taken into account when writing the treatments.
Illustrations follow the format of the Flora of North America. I liked the illustration of sedges done by Susan Reznicek. Susan is a botanist and you can tell it from her illustrations. You can appreciate the illustrations, if you go to the Flora of North America web site and view them in close to their original size.
The Flora of North America is available online from the web site: http://www.fna.org/FNA/volumes.shtml Navigation in the web site is easy and the species descriptions are linked to the illustrations. Once you know what you are looking for, you can find it easily on the web site. On the other hand, the book is a good investment. You can be sure that for at least the next thirty years you won't get anything better in the sedge family in North America than this FNA volume.
The Species Plantarum Project is an initiative by a worldwide consortium of taxonomists to write and publish a Flora of the vascular plants of the world. The project operates under the auspices of the International Organization for Plant Information (IOPI), a Commission of IUBS. As written in the Introduction to the series, "Species Plantarum aims to provide in concise format, and with standardized data fields, basic taxonomic information on the vascular plants of the world, including accepted names and synonyms with bibliographic data, types of names, keys and descriptions from family to varietal levels, geographical distributions, ecological information and other related matters, and to publish it in both hard copy and electronic form." Detailed review of the project is provided by Brummitt et al. (2001). As of today, the Introduction to the series by A.E. Orchard as well as accounts of six families were published.
The four out of six family accounts already published are rather short, representing one species for Welwitschiaceae and Prioniaceae, three species for Stangeriaceae and ten species for Irwingiaceae and the purpose of their publication is to show what family treatments "should look like". The family account of Schisandraceae comprises 39 species in two genera. For more information on this series see: http://platnet.rbgsyd.gov.au/iopi/iopispp1.html
In fact, the family treatment of Juncaceae (440 species in 7 genera), comprising 765 pages and including 537 distribution maps for the first time shows the real potential of the whole project. The volume was prepared in a wide international collaboration of 21 authors under the editorship of Jan Kirschner, with the help of three advisors to the whole family treatment (two of them also contributed as authors).
There are two important points that I would like to stress. The first, authors of this family treatment not only summarized present knowledge on the genus (adding quite a lot of new information while preparing this account), but also pinpointed the gaps in our knowledge about this family. This is important for directing further research. Secondly, the whole world treatment of this family has shown serious gaps in the local and general Red Lists of vascular plants. Out of the 22 species names listed in the 1997 IUCN Red List of Threatened Plants, nine were found to be synonyms of widely distributed taxa, two are taxonomically doubtful and only 11 of them are really threatened. On the other hand, an additional 34 species not listed in 1997 were shown as threatened ones (Kirschner & Kaplan 2002). Many taxonomists are aware of the inaccuracies in the Red Lists of all kinds, but the numbers provided as a result of the study of this particular family are alarming and illustrate the real need of world scale taxonomic treatments. Clearly, we cannot protect something that we do not know.
The account of the family Juncaceae was the first exercise on a large family in this project and thus naturally pinpointed several problems to be solved. For instance, in spite of the detailed guidelines and really precise editorial work of Anthony E. Orchard and his assistant editors, the format of the accounts still suffers from a few "child diseases", e.g. inconsistency in the use of ISO1 or ISO2 standards to transliterate the Cyrilics in journal titles. Another item, maybe important only from the purely European point of view, are references to Czechoslovakia (CZE) or Yugoslavia (YUC) in the distribution data, in spite of the fact that these coun?ries ceased to exist in their original shape a decade ago. Their division is reflected in the second edition of Brummitt's World Geographical Scheme for Recording Plant Distributions (Brummitt 2001) only on level 4 and not on level 3 to which distribution data are referred to in Species Plantarum. However, the preparation of various checklists or Red Lists for the purpose of national legislature or for decision makers on all levels, desperately need the information on the presence or absence of the species on country levels. In addition, both these regions are phytogeographically very variable and from this point of view certainly do not represent natural units.
To sum up, the publication of the series Species Plantarum: Flora of the World is a major achievement in taxonomy and in the international cooperation of taxonomists of all continents, and hopefully the new volumes will follow in a regular schedule (the account of the family Chrysobalanaceae is already in the works). It should be found on the shelves of all important botanical libraries, but also on the book shelves of those who deal with threatened plants or those interested in biogeography and other related subjects.
This is definitely the most beautiful volume of the Flora of North America north of Mexico published so far. The volume treats 733 species in and six named interspecific hybrids. The subfamilies treated are Aristidoideae, Arundinoideae, Centothecoideae, Chloridoideae, Danthonioideae, and Panicoideae.
The work on this treatment started in about 1986 as a revision of A.S. Hitchcock's 1951 Manual of Grasses of the United States, 2nd ed. rev. A. Chase. The Manual revision was well underway when the Flora of North America finally took off. I doubt that the work would have ever been finished without the editorial effort of Mary Barkworth, whose energy I have always admired. I did not count how many people coauthored treatments to this volume, but the result is relatively coherent and uniform. Quite a feat, as I know that some authors submitted their treatments in handwriting.
The format resembles that of the Flora of North America, but in some features it deviates from it. On the negative side, I did not like pooling synonyms in the index-like list at the end of the volume, synonyms without citing authorities in alphabetical order. The names in the treatment don't have the full citations, only the authorities with the sources. The distribution of each species is illustrated with detailed distributional maps, much better than, for instance, in the Cyperaceae volume, but on the other hand, the text doesn't have any distributional summary, i.e., accounts of Canadian provinces and the US states as in the other FNA vol?mes.
Illustrations are definitely the most positive feature of this volume. Each species (with exception of one, they say) are illustrated and the illustrations are mostly on full-size plates. Both grass habit and many important details are depicted for most species. The botanist and botanical artist Linda Vorobik put together a team of six highly skilled artists who all matched their styles well and produced superb illustrations. I noticed that all species of the same genus were all drawn by the same artist, hence the style is consistent for all the species within each genus. Can you imagine having to draw all the 70 species of Muhlenbergia?
My main complaint is that this volume deals mostly with the taxa that occur in eastern or southeastern United States; the Pacific Northwest is represented by a few members. Unfortunately, the authors could not do too much to rectify this distributional anomaly. However, it makes me anticipate all the more eagerly the first part of the Poaceae family that will cover most of our taxa that grow in the Pacific Northwest.
The illustrations and treatments from the second of the two Flora of North America volumes is currently being made available at http://herbarium.usu.edu/grassmanual/ As many works of this dimension, this volume is not without mistakes and errors. In order to see the corrections and print out Errata, visit the following web site: http://herbarium.usu.edu/grassmanual/FNA25/default.htm
Mary Barkworth and all the others involved in the preparation of this volume should be congratulated on this great achievement. It is a job well done!