[APWG] CANADIAN LIST OF NATURALIZED ALIEN TREES AND SHRUBS

[Patricia_Ford at fws.gov]

FYI-

CANADIAN LIST OF NATURALIZED ALIEN TREES AND SHRUBS - SOME
             ADDITIONS AND RECENT INFORMATION - 1

From: Paul M. Catling (1) and Frank Lomer (2)

(1) Biodiversity, National Program on Environmental Health,
    Agriculture and Agri-food Canada, Wm. Saunders Bldg.,
    Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6
    [catlingp at agr.gc.ca ]
(2) 711 Colborne St., New Westminster, BC, Canada V3L 5V6
    [lomerlomer at hotmail.com ]


Continuing interest in the threat of invasive alien species has
required a series of  updates to the checklist and related
information

Here the term "naturalized" is used since "invasive" has acquired
the meaning of being problematic as a result of displacing native
or cultivated species. Some plants that have become naturalized
(reproducing and spreading on their own outdoors) are not
necessarily problematic. Of course a species that has established
may not yet be a serious problem, but it may become problematic,
in which case the term "invasive" would apply to it. For
information on the risk of invasiveness of woody plants, see the
hierarchical predictive model produced by Reichard and Hamilton
(1997).

JUGLANDACEAE

Japanese Walnut, _Juglans ailanthifolia_ Carr.

This species was excluded from the British Columbia flora due to
lack of persistence (Douglas et al. 1999). However, _Juglans
ailanthifolia_ is persistent and established in British
Columbia. It is becoming more frequent in Greater Vancouver,
usually near river shores and water edges. It is commonly
grown, much more so than the eastern butternut (_Juglans
cinerea_ L.), and has apparently reached the point where
the escaped trees are now old enough to start new trees.

Further east in the upper the Fraser Valley there are dozens of
trees visible along Highway 1 from Agassiz to Hope. On
uninhabited Herrling Island in the Fraser River there is a huge
plantation of _Juglans ailanthifolia_, possibly including hybrids
with _J. cinerea_, and trees have escaped there as well. It is
anticipated that this species will be added to the flora of BC in
the next update.


Specimens: Rivershore, Herrling Island, 5 km east of Agassiz, BC,
    49.2486 °N, -121.6861 °W, 1995-10-28, Frank Lomer 95-232
    (UBC); Dyke shore, unnamed island in Fraser River, 2.5 km
    west of Port Mann Dridge, Surrey, BC, 49.2202 °N,
    -122.8468 °W, Frank Lomer 97-593 (UBC).


English Walnut, _Juglans regia_ L.

Although occasionally grown in southern British Columbia, not
previously reported as an escape from cultivation in Canada. At
least at present, its limited spread at Osoyoos (specimen cited
below) does not represent or suggest a serious problem. In the
vicinity of Osoyoos there are trees of various ages from less
than 1 m tall to several m tall along roads, ditches and fence
lines. These trees appear not to have been planted. Some of the
larger of these are producing fruit. These observations suggest
reproduction of spreading plants and the species is thus added to
the list, although Whittemore & Stone (1997) have suggested that
although seedlings are occasionally reported in North America,
they rarely if ever live to maturity. English Walnut is easily
distinguished from most other walnuts by the glabrous, instead of
pubescent fruits, and by the entire, instead of serrated
leaflets. Northern California Walnut (_Juglans hindsii_ Jepson ex
R.E. Smith) has been widely introduced outside its California
range for grafting English Walnut. It is now naturalized in many
areas of the west, but can be distinguished by its serrated
leaflets.

Some of the _Juglans hindsii_ X _J. regia_ hybrids are more
difficult to identify (Whittemore & Stone 1997).

Specimen: Open roadside of Lakeshore Drive, East Osoyoos,
    49.0172 °N, -119.4345 °W, 2007-06-04, P.M. Catling (DAO).

TAMARICACEAE

Salt-Cedar, _Tamarix ramosissima_ Ledebour

A large shrub or small tree, Salt-Cedar is native to Africa and
Eurasia. It was introduced into the to the western U.S. in the
early 1800s for use as an ornamental and to control erosion. The
U.S. Department of Agriculture has ranked it as one of the most
harmful invasive species in the U.S. It depletes groundwater,
increases surface salt concentration and degrades habitats for
native species of plants and animals. Its groundwater-absorbing
qualities may be adding to the severity of the drought in the
western U.S. Baum (1967) had one record of it in Canada from the
Experimental Station in Morden where it was presumably
cultivated. In 2007 it was found growing without cultivation and
apparently not planted in damp ditches near Penticton (specimen
cited below) and on the sandy shores of Osoyoos Lake (at East
Osoyoos etc.) where both small and large plants occurred with
poplars and native vegetation suggesting natural spread. It was
also observed in roadside ditches near Osoyoos.  An unidentified
species of _Tamarix_ was also observed along a sandy path above
Osoyoos Lake on the Osoyoos Indian Reserve northeast of Osoyoos.
Although these were the only observations of apparent spread, it
was observed many times in the Okanagan valley in cultivation as
a garden ornamental. In at least some situations the cultivated
plants fail to produce seed so more study is required to
determine the origin of the apparently escaped plants.

Although Baum reported specimens of _Tamarix chinensis_ Lour.
from British Columbia, Ontario, Manitoba and Quebec and noted
that it is "cultivated and naturalized to a large extent", it is
not clear if there was ever any evidence of naturalization in
Canada. Baum also reports having seen records for _Tamarix
parviflora_ DC. in British Columbia, Ontario and Nova Scotia. It
is not clear whether or not these referred to cultivated or
escaped plants but it was excluded from the British Columbia
flora by Douglas et al. (2000) as a result of not persisting in
the wild.

_Tamarix ramosissima_ differs from other North American species
in having all of the staminal filaments inserted under the lobes
of the disk but near the margin, 4-merous flowers and sepals more
or less entire.

Specimen: ditch on E side of hwy 97 on NW side of Penticton,
    49.5012 °N, -119.6171 °W, 2007-06-04, P.M. Catling (DAO).


For information on other woody plants, either recently
established or spreading in Canada, see Catling et al. (1996),
Catling & Carbyn (2005) and Catling (2005, 2006, 2007).

LITERATURE CITED

Baum, B. 1967. Introduced and naturalized Tamarisks in the
             United States and Canada (Tamaricaceae). _Baileya_
             15: 19- 25.
Catling, P.M. 1997. The problem of invading alien trees and
             shrubs: Some observations in Ontario and a Canadian
             Checklist. _Canadian Field-Naturalist_ 111: 338-342.
Catling, P. M. 2005. Identification and status of the
             introduced Black Pine, _Pinus nigra_, and Mugo Pine,
             _Pinus mugo_, in Ontario. _Canadian Field-Naturalist_
             119(2): 224-232.
Catling, P.M. 2006. False Indigo-bush, _Amorpha fruticosa_ L.,
             an addition to the Ottawa flora and a possible native of
             the Ottawa valley. _Trail & Landscape_ 40(3): 150-154.
Catling, P.M. 2007. Weeping Forsythia, another shrub naturalized
             in Canada. _Botanical Electronic News_ 378: 1-2.
Catling, P. M. and S. Carbyn. 2005. Invasive Scots Pine (_Pinus
             sylvestris_) replacing Corema (_Corema conradii_)
             heathland in the Annapolis valley, Nova Scotia, Canada.
             _Canadian Field-Naturalist_ 119(2): 237-244
Catling, P.M., M.J. Oldham, D.A. Sutherland, V.R. Brownell,
             and B.M.H. Larson. 1996. The recent spread of Autumn-olive
             (_Elaeagnus umbellata_) into southern Ontario, and its
             current status. _Canadian Field-Naturalist_ 111(3):
             376-380.
Douglas, G.W., D. Meidinger and J. Pojar. 2000. _Illustrated
             flora of British Columbia. Vol. 5, Dicotyledons
             (Salicaceae through Zygophyllaceae) and Pteridophytes_.
             British Columbia Ministry of Forests. 389 p.
Douglas, G.W., D. Meidinger and J. Pojar. 1999.  _Illustrated
             flora of British Columbian Vol. 3, Dicotyledons
             (Diapensiaceae through Onagraceae)._ British Columbia
      Ministry of Forests. 423 p.
Reichard, S.H. and C.W. Hamilton. 1997. Predicting invasions
      of woody plants introduced into North America.
      _Conservation Biology_ 11(1): 193-203.
Whittemore, A.T. and D.E. Stone. 1997. Pp. 425-428 in
             _Flora of North America_ Editorial Committee, eds.
             _Flora of North America north of Mexico. Vol. 3,
             Magnoliophyta: Magnoliidae and Hamamelidae._ Oxford
             University Press, New York, NY. 590 p.