ISSN 1188-603X

No. 444 October 11, 2011 Victoria, B.C.
Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2


From: Paul M. Catling and Gisèle Mitrow, Agriculture and Agri-Food Canada, Environmental Health, Biodiversity, Saunders Bldg., Central Experimental Farm, Ottawa, Ontario K1A 0C6 Canada

All native Canadian mistletoes are very small plants without conspicuous leaves (genus Arceuthobium). So where does our leafy Christmas Mistletoe come from and what is it? There are two possibilities: (1) The European Christmas Mistletoe, Viscum album L., is sometimes imported from Europe,and (2) the North American Christmas Mistletoe, Phoradendron serotinum (Rafinesque) M.C. Johnston is sometimes imported from the southern United States, perhaps mostly from the southeast as subsp. serotinum (previously P. flavescens, but see Nickrent et al. 2010 regarding the complex nomenclature of this taxon), or from Texas or Oregon as subsp. tomentosum (DC.) Kuijt (Hawksworth & Wiens 1993, previously P. villosum). It appears that almost all importation of Christmas Mistletoe into Canada has been, and still is, P. serotinum from the United States, but there have been a few instances of importation from Europe involving Viscum album.

The European Mistletoe (Viscum album) is established in Canada in Victoria, British Columbia (Dorworth 1989, Heide-Jorgensen 2008), but its locations are kept secret, for fear that it would be eliminated as an invasive potentially damaging to North American trees. The plants are said to have been brought over by a returning war veteran in 1945. There were only a couple left in early 2000 and it had not spread. At one time there was also a plant in the Royal Botanical Garden in Hamilton, Ontario, growing in an Apple tree.

European Mistletoe is well established in California where it occurs in at least three counties (Hawksworth & Wiens 1993). Since the two species generally do not occur together in regions covered by floras, there are very few keys that include both of them. The Flora North America volume including mistletoes has yet to be produced. However, the Jepson Manual (Hawksworth & Wiens 1993) does include Phoradendron serotinum and Viscum album in a key. Both are also included in Rehder's (1937) manual of cultivated trees and shrubs. Neither of these however, includes a reference to the major difference in branching which we were reminded of by mistletoe expert Job Kuijt. Using these and other sources as well as the examination of herbarium specimens we have developed a key. Here the characters in each couplet are presented in what we consider the order of their usefulness.

1a. Stems branching, or forking, into two or more equal parts (pseudodichotomous); berry 6-10 mm in diameter; flowers or berries in small clusters (dense cymes) of 1-5; flowers not sunken into the branch axis; anthers several-chambered; flower parts generally 4 Viscum album L.

1b. Stem branching with a main axis, not forking (percurrent); berry 3-6 mm in diameter; flowers or berries many and in more or less interrupted spikes;flowers sunken into the branch axis; anthers 2-chambered; flower parts generally 3 Phoradendron serotinum (Rafinesque) M.C. Johnston

The two species vary in leaf shape, so this is of limited value in identification. A key is available for the three subspecies of Phoradendron serotinum in Kuijt (2003). One subspecies (subsp. serotinum) is found in the eastern and midwestern US, one in Mexico (subsp. angustifolium in Mexico) and two (subspp. macrophyllum and tomentosum) in the western US. There are also subspecific taxa (varieties) of V. album which occur across Eurasia. The closely related Viscum coloratum (Komorov) Nakai, with its yellow berries, was introduced to Switzerland from Korea in the 1980s and is attracting increasing interest as a source of medicinal compounds (Park, 2000).

Outside of the north temperate region, the species used as Christmas Mistletoe may depend on what is locally available and the custom is less well developed. In parts of Australia, it is Amyema sanguineum (F. Muell.) Dans. which is sometimes hung at Christmas. While our Christmas Mistletoes, in the family Viscaceae, have inconspicuous flowers, the Australian plant, like many other species in the family Loranthaceae, has very showy, tubular red or yellow flowers. Since the Australian plant is in a different family, there are many other differences that are less readily observed (Calder and Bernhardt 1983, Table 1, p. 9).

We see less real Christmas mistletoe and more of the plastic product now than in the past. There are probably several reasons for this. All mistletoe for trade is wild-collected and in some places it has become scarce due to unsustainable harvest and/or changes in the landscape. It is still readily available on the web, and most of the product advertised originates in the United States and is Phoradendron serotinum.

The former harvest of Viscum album in Apple orchards in England may have been sustainable to some extent and possibly benefited the host trees by keeping the mistletoe plants relatively small. European Mistletoe is also sometimes said to be cultivated. This appears to be mostly for medicinal compounds (Ramm et al. 2000), the usefulness of which is still controversial. Since plants develop slowly, it seems unlikely that cultivation for the Christmas trade will become widespread and profitable.

Other reasons why we are seeing less may be the increasing concern over importation of: (1) plants that may escape and affect native species; and (2) plants that are poisonous. These may not be major concerns because there have been few deaths as a result of ingestion and the climate over most of Canada is too cold to allow the most frequently imported species (Phoradendron serotinum) to survive. However, both species are listed by the Canadian Food Inspection Agency (CFIA) among substances determined to be an unacceptable health risk for human and/or animal health (CFIA 2011). At present mistletoes are not regulated in Canada and thus we can expect to continue to see real plants imported for Christmas and weddings.


We very much appreciate the help of mistletoe experts Job Kuijt and Daniel Nickrent in preparing this note. Conservationist Dave Fraser provided helpful comments.


Calder M. & P. Bernhardt. 1983.
The biology of mistletoes. Academic Press, New York. 348 p.
Canadian Food Inspection Agency. 2011.
Appendix A: Substances determined to be an unacceptable health risk for human and/or animal health.
Dorworth, C.E. 1989.
European Mistletoe (Viscum album subsp. album) in Canada. Plant Disease 73(5): 444.
Hawksworth, F.G. & D. Wiens. 1993.
Viscaeae, Mistletoe family. Pp. 1092-1097 in J.D. Hickman, ed. The Jepson Manual, higher plants of California. University of California Press, Berkeley.
Heide-Jørgensen H.S. 2008.
Parasitic Flowering Plants. Koninklijke Brill NV, Leiden, The Netherlands. 438 p.
Kuijt, J. 1969.
The Biology of Parasitic Flowering Plants. University of California Press, Berkeley, California . 248 p.
Kuijt, J. 2003.
Monograph of Phoradendron (Viscaceae). Systematic Botany Monographs 66: 1-643.
Nickrent, D.L., D.E. Boufford & J. Kuijt. 2010.
(1986) Proposal to conserve the name Viscum serotinum (Phoradendron serotinum) against V. leucarpum (Viscaceae). Taxon 59(6): 1903-1904.
Park, W.-B. 2000.
Chapter 4, Korean Mistletoes and other east-Asian populations. Pp. 45-60 in Arndt Büssing, Mistletoe, the genus Viscum. Harwood Academic Publishers, Amsterdam. 266 p.
Ramm, H, K. Urech, M. Scheibler and G. Grazi. 2000.
Chapter 6, Cultivation and development of Viscum album L. Pp. 75-94 in Arndt Büssing, Mistletoe, the genus Viscum. Harwood Academic Publishers, Amsterdam. 266 p.
Rehder, A. 1937.
Manual of cultivated trees and shrubs, hardy in North America. The MacMillan Company, New York, NY. 930 p.


From: Dimitar Bojantchev

Cortinarius xanthodryophilus D. Bojantchev & R.M. Davis was described recently from California as one of the most commonly occurring Cortinarius species under oak (Bojantchev & Davis 2011). The species belongs to the genus Cortinarius subgen. Phlegmacium, and is a member of the extensive clade of calochroid cortinarii, most of which were previously known as the subgenus Bulbopodium. The species is characterized by predominantly light to dark yellow colors, distinctly emarginated bulb, weak alkali reaction, and association with oaks. Based on phylogenetic analysis of the nrITS gene region, it is placed in the pseudoglaucopodes clade. Despite the diverse external coloration of the members of that clade, the spore size and macro chemical reactions, which are rather well evolutionary conserved characters, remain very similar.

This species is common in California under live oak (Quercus agrifolia Née). In the Sierra Nevada foothills it occurs under interior live oak (Q. wislizeni A. DC.) and canyon live oak (Q. chrysolepis Liebm.). In northern California coastal areas it was collected under tanoak (Notholithocarpus densiflorus [Hook. & Arn.] Manos, Cannon & S.H. Oh). In all the Californian localities, Cortinarius xanthodryophilus grew in association with evergreen trees. There is also a collection from Vancouver Island, British Columbia, under deciduous Garry oak (Quercus garryana Dougl. ex Hook.). [University of British Columbia herbarium specimen was originally identified as Cortinarius subfulgens: UBC F17181, Elkington Property near Duncan, British Columbia, Canada; growing under Quercus garryana. Coll.: O. Ceska, November 23, 2002, GenBank #: GQ159771.]

The description of the species is Open Access and can be retrieved from Mycotaxon 116 online at

In addition, the authors maintain a website where they provide exhaustive pictorial treatments of the species they describe.

[Editorial comment: Dimitar Bojantchev has been an avid amateur mycologist for several years, but his primary research interests rest with the most challenging genera of macromycetes, such as Cortinarius and Russula. He teamed with Prof. Mike Davis (UC Davis) in running an extensive molecular analysis of hundreds of collections from California, the Pacific Northwest and Europe. They are aware of a number of undescribed species in both Cortinarius and Russula, as well as the intricacies of the challenging species complexes that occur in the broader Pacific Northwest. There are several taxonomic papers currently in print. Dimitar Bojantchev is active on the NAMA club speaker circuit and will attend the Northwest Mushroomers Association in Bellingham, WA on November 10, 2011, where he will discuss advanced amateur mycology, molecular methods and the genus Cortinarius.]

Literature cited

Bojantchev, D. & R.M. Davis. 2011.

Cortinarius xanthodryophilus sp. nov. - a common Phlegmacium under oaks in California. Mycotaxon 116: 317-328.


From: Barbara L. Wilson, Carex Working Group, 2710 Emerald Street, Eugene, Oregon 97403 e-mail: (abbreviated article was originally published in the Oregon Flora Newsletter Volume 17, No. 1, August 2011)

The Carex Working Group is thrilled and relieved! We're done writing the grass treatment for the Oregon Flora Project.

Mystified that the work was taking more than a year, friends would say "Writing the grass treatment must be easy, now that the Flora of North America (FNA) grass volumes are out." And we would want to scream. Writing the Oregon grass treatment has not meant simply stripping all of the non-Oregon grasses out of the FNA treatment.

What did we really do?

First, we sought to write a simple key to genera. Early leads of the FNA key are intimidating. Very different grass keys from the Jepson Manual (JM) and Vascular Plants of the Pacific Northwest (H&C) both work, but neither includes all Oregon species. We started with the JM key and consulted FNA to add missing Oregon taxa.

Nick Otting and Richard Brainerd ("the guys") tested this key by running all 354 Oregon grass species through it. Students in our grass identification mini-classes gave us different perspectives on the keys, causing us to tweak wording or totally rewrite sections. The final version of the key (number 23!) is much different from the first.

For species within genera, we started with whatever key we liked best, from FNA, JM, H&C, or other sources. Poa expert Robert Soreng wrote a key for us to that complex genus. Sometimes there was no good key for Oregon and we wrote our own. Cindy Roche read the draft keys critically, providing many helpful suggestions.

Writing the genus treatments was a multi-step, iterative process.

  1. I consulted floras or OFP's morphology database to write treatments for all species. Each treatment included a genus description, key to species, species descriptions, and sometimes habitat, range, and discussion.
  2. Once the first drafts for all species were finished, I worked through each genus, trying to understand it. I might modify the key or description, write discussion sections, or add habitat or range. I might note problems needing further work.
  3. Then the guys took over each genus treatment. They keyed every species. They rewrote keys, modified descriptions, provided habitat information, and wrote or rewrote summary discussions. Sometimes the draft pages were virtually covered with scribbles, glyphs, and arrows!
  4. Then I would rewrite and the guys would retest until we were satisfied.

Published technical information was mostly accurate, but not always. Maybe FNA reported awns as 8-15 mm long but we found some 20 mm long. Maybe the lemmas are longer elsewhere, so FNA reports them to be 5-15 mm long, but Oregon's longest are 10 mm long. Lemmas of Festuca subulata are reported to be "glabrous, sometimes sparsely scabrous" but occasional Oregon specimens have hairy lemmas. We found Cynosurus echinatus and Scribneria bolanderi individuals nearly twice as tall as reported in FNA.

We annotated more than 900 specimens from the combined herbaria at OSU. Some annotations confirmed identities; others corrected errors. We were able to remove taxa from the Oregon checklist (e.g. Achnatherum occidentalis subsp. occidentalis, Festuca minutiflora, Hesperostipa comate subsp. intermedia, Podagrostis aequivalvis, and Thinopyrum junceum) and add others (e.g. Agropyron fragile and Thinopyrum pycnanthum). Bromus arvensis made a mess of our key because its traits bridge the gaps between other little weedy bromes, so we were happy when we borrowed the only Oregon specimen and found it had been misidentified.

Most of our distribution information came from the Oregon Plant Atlas. When OPA mapped seemingly out of range records, we examined the voucher specimens if possible. We reported apparently erroneous records to OFP for correction. Embarrassingly, we sometimes deleted observations we had made.

We made taxonomic judgments. We chose to recognize Mountain Brome, often called Bromus marginatus, as a subspecies of B. carinatus. FNA recognizes subspecies or varieties of Bromus hordeaceus, Deschampsia cespitosa, and Vulpia octoflora, but they aren't distinct in Oregon; we omitted them. However, we tentatively recognized the controversial subspecies of Thinopyrum intermedium and Muhlenbergia mexicana.

Calamagrostis gave us trouble. The FNA key looks simple, but the traits are surprisingly hard to interpret correctly. We rewrote the key in major ways, tested, and rewrote. By comparing specimens, we learned that many Oregon records were misidentified. By the end, the ranges of most Oregon Calamagrostis species were radically reduced, the description for C. tacomensis was significantly modified, and the key cycled back to something similar to the original.

We fought our computers. Faced with spell-checking technical terms for grass morphology, Microsoft Word offered to import dictionaries for "French France" or "Portuguese Brazil." Dick's computer preferred Italian. We refused on the grounds that the treatments were English and we could teach the software how to spell culm, panicle, spikelet, glume, etc. Spurned, the computers refused to spell-check the technical descriptions at all.

At last we were done. We had written treatments for Oregon's 354 grass species. (Except Poa - we were still working on Poa). Time to celebrate! We turned our treatment in to OFP. OFP was not excited. We considered this done? Nothing was in OFP format. Hadn't we read the Contributor's Guide? Oops. When we started there hadn't been a Contributor's Guide. Now we spent a month reformatting the treatments. We tried to shorten the descriptions to the recommended 100 words. That was hard, especially in big genera. I cut Elymus descriptions an average of 27%, but they still averaged 175 words.

Right near the end, one of us was inspired to include the most commonly occurring named wheatgrass hybrids in our treatment. Nearly any two species of Elymus, Hordeum, Leymus, Pascopyrum, and Pseudoroegneria might hybridize if they grow together. Each hybrid is variable. We sat down for three solid days of examining wheatgrass hybrids. At last I wrote a key. It might even work.

In February we turned in all the treatments for Oregon grasses. Joy, oh joy, oh joy. Now OFP taxonomic editor Stephen Meyers gets to read all 400+ pages. Have fun, Stephen!

[The Poaceae treatment will be posted by the Oregon Flora Project at some time soon. We have found that for the Poaceae, "soon" is a longer period of time than any of us might have expected.

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