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Rithet's Bog LogoTreacherous Beauty Threatens Wetlands

The Victoria Naturalist, Vol. 62.2, Sept/Oct 2005 - Sharon Godkin

On a recent trip into Rithet’s Bog (24 July 2005; walk led by Sharon Hartwell) I encountered a plant I had never seen before. It looked like a strikingly beautiful giant Willowherb. My first thoughts were: “Wow!! What is that? Will it grow in my garden?” The larger of the two specimens seen was taller than I could reach, making it at least 2 m tall. This plant arose from a single stem about 2 cm diameter, and branched upwards. The long leaves (up to 10 cm) were lanceolate, toothed, and mostly opposite. Both stem and leaves were covered with fine soft hairs. Purplish-rose flowers, at least 3 cm across, bloomed from the upper leaf axils. The slightly cupped flowers had the overall structure of Willowherb blossoms, but the petals were broad and shallowly notched with 2 rounded lobes, making the flowers showier than those of our usual willowherbs. Frosted white crosses, the 4-lobed stigmas, bobbed above the flowers on thin, barely visible styles.

A brief read through botanical keys ( Hitchcock and Cronquist, 1973; Douglas, et.al., 1999) identified it as Epilobium hirsutum, the Hairy Willowherb. It is illustrated as a native wildflower by Niering and Olmstead (1996). It had been reported from areas of Washington State, one location in the Fraser Valley, and one in the Okanagan. National Audubon Society’s “Field Guide to North American Wildflowers - Eastern Region (1979). John Pinder-Moss, the Botany Collection Manager at the Royal BC Museum, indicated he has collections from the Wilkinson Road/West Burnside area (21 June 1992; by Adolf Ceska and Kelowna, July 11 1998; by George Scotter ). Sharon Hartwell had found it in Rithet’s bog three years ago; after it was identified by Matt Fairbarns, she removed it. But it has returned! It appears that it is being reintroduced by water flowing into the bog from storm drains.

A “Google” search brought up several pages of links. One of the most informative sites is <http://www.ecy.wa.gov/programs/wq/plants/weeds/willowherb.html>. The more I read the more horrified I felt - definitely NOT a candidate for my garden! And definitely not a species we should allow to become established in our area. It is an impressively adaptive perennial, growing from sea level to 2500 m. It prefers wet to damp areas, colonizing riparian areas, ditches, wetlands, pastures, waste places, roadsides, meadows and gardens. Initially shade intolerant, once established it is somewhat shade tolerant. In wetlands it grows aggressively, crowding out all other species except Purple Loosestrife (Lythrum salicaria). In fall, it out-competes Purple Loosestrife; in spring the reverse happens - Purple Loosestrife grows faster. It reproduces by wind-blown seeds, spreading and branching rhizomes, and a type of stolon. The shoots die down in fall, but the rhizomes remain to resume growth the following spring.

Hairy Willowherb is a native of Eurasia and has been spread by people: as a garden ornamental, a weed, and in ships’ ballast. It became established in the northeastern USA about 140 years ago, and has been moving west ever since. It was first collected in Washington State in 1965, where it is being spread by gardeners who consider it a replacement for Purple Loosestrife. The latter is listed in Washington as a noxious weed; but Hairy Willowherb is listed only as “wetland and aquatic weed quarantine”, and its spread is being monitored. It is found in nine states of the USA, and throughout southeastern Canada. It has various degrees of weed listings depending on the location, up to noxious weed status. It is listed in The Global Compendium of Weeds (http://www.hear.org/gcw) ; so why is it being sold as an ornamental?? No responsible gardener should grow it, despite its beauty. I’m sure Sharon Hartwell and the Rithet’s Bog Conservation Society would greatly appreciate any volunteers (especially with hip waders) willing to help remove this lovely weed from the bog before it becomes irreversibly established.

Literature Cited

Douglas , G.W., D. Meidinger, and J. Pojar. 1999. Illustrated Flora of British Columbia. Vol. 3: Dicotyledons (Diapensiaceae through Onagraceae). B.C. Ministry of Environment, Lands & Parks and B.C. Ministry of Forests. Crown Publications, Victoria.

Hitchcock C.L. and A. Cronquist. 1973. Flora of the Pacific Northwest. University of Washington Press, Seattle, WA.

Niering, W.A. and N. C. Olmstead. 1996. National Audubon Society Field Guide to North American Wildflowers –Eastern Region. Alfred A. Knopf, New York, NY.

 

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