Recovery Strategy for the Common Hoptree in Canada [Final] 2012: Species Information

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Date of Assessment: November 2002

Common Name: Common Hoptree

Scientific Name: Ptelea trifoliata

COSEWIC Status: Threatened

Reason for Designation: A species of restricted range in Canada with a small population size occurring primarily along sandy shoreline habitats. It has experienced substantial losses at some sites from cottage land development, damage to habitats by increasing numbers of nesting cormorants and other unknown factors. A newly recognized potential threat of unknown impact is posed by a recently discovered twig-boring beetle, which is causing damage to flowers and large portions of the tree crown.

Canadian Occurrence: Ontario

COSEWIC Status History: Designated Special Concern in April 1984. Status re-examined and up-listed to Threatened in November 2002. Last assessment based on an update status report.


* COSEWIC = Committee on the Status of Endangered Wildlife in Canada.

The Common Hoptree, which has likely always been rare in Canada due to the restricted range of its habitat, is listed as Threatened on both Schedule 1 of the Species at Risk Act (SARA) and the Species at Risk in Ontario List (Ontario Ministry of Natural Resources [OMNR] 2010) under the Endangered Species Act, 2007. It is considered Vulnerable in Ontario (S3) and Canada (N3), although Secure in the United States (N5) and around the globe (G5) (NatureServe 2011). The species is introduced in Qu├ębec (Rousseau 1974). Less than 0.2% of the species' range is found within Canada (Little 1976).

The Common Hoptree (Ptelea trifoliata) is a short-lived[1], deciduous[2], typically dioecious[3] tree that grows up to 10 m high and 24 cm in diameter (Waldron 2003), with a reddish-brown, often branched trunk. Alternate, sharp-pointed, nearly stalkless, compound leaves of three leaflets have smooth to very shallow, toothed margins and a wedge-shaped base (Farrar 1995). Their pungent, citrus odour accounts for its other common name, "stinking-ash". Fragrant, cream-coloured flowers are produced in early summer. The fruit, or samara, containing one or two centrally located seeds, surrounded by a flat, veined wing, is dispersed in late autumn and winter (Waldron 2003). Ambrose (2002) provides additional details.

Key characteristics of the distribution of Common Hoptree in Canada are:

Figure 1: North American distribution of all Common Hoptree subspecies (Ambrose and Aboud 1984).

Figure 2: Canadian distribution of the Common Hoptree (Note: Not all points represent GPS-level accuracy).

Since the 2002 COSEWIC assessment, new information has become available. Key characteristics of the population sizes and trends of Common Hoptree in Canada are:

Table 1: Extant Common Hoptree Population Locations.
Core Area Population City/Township
Middle Island Middle Island, Point Pelee National Park (critical habitat parcel #225_1) Township of Pelee
Pelee Island Fish Point Provincial Nature Reserve (#255_2)
Red Cedar Savanna: NCC's Richard & Beryl Ivey/Stead-Martin property (#255_3)
Stone Road Alvar (#255_4, #255_5, #255_6, and #255_7): including Mill Point and South Bay Shore
West Shore Pump Station: includes the rocky limestone wooded area on west side of the island near abandoned quarry (#255_8)
Middle Point: NCC's Novatney (#255_9 and #255_11) and Florian Diamante/Brown's Road properties (#255_10)
Lighthouse Point Provincial Nature Reserve (#255_12)
Essex County Holiday Beach Conservation Area (also known as/Big Creek Marsh) Amherstburg
1.5 km west of Comet
Lypps Beach Essex
Colchester Public Beach
1 km north of Colchester
Fox Creek Conservation Area
Cedar Beach Conservation Area (#255_13) Kingsville
Seacliff Beach (west of Leamington ferry dock) Leamington
Point Pelee National Park (#255_14)
Hillman Marsh Conservation Area sand spit/barrier beach (#255_15)
Walpole Island First Nation Chematogan: River Road Walpole Island First Nation
Old Ferry Road and Snye Roads
Rondeau PP/Erieau (Municipality of Chatham-Kent) Erieau/Rondeau: Laverne Kelly Memorial Park and adjacent lands, Erieau (#255_16), and Rondeau PP South Point barrier beach (#255_17 and #255_18) and Marsh Trail Erieau and Morpeth
Rondeau PP Marsh Trail Morpeth
Rondeau PP Northwest (Lakeshore Road and dunes) (#255_19 and #255_20)
3.5 km east of Thamesville Thamesville
Port Burwell PP (Elgin County) Port Burwell (formerly Iroquois Beach) PP (#255_21) Bayham
Hardy Road Brantford
RM of Niagara Nickel Beach (#225_22 and #255_23) and Lorraine (Cassaday) Point (#255_24) Port Colborne
Lorraine Bay (#255_25)
Cedar Bay Road beach access (#255_26)
Sherkston Shores west (#255_27 and #255_28)
Point Abino: Sherkston Shores east (Park) (#255_29), Pleasant Beach Road beach access (#255_30), Point Abino west shore (#255_31), Point Abino (#255_32), Point Abino peninsula sandland forest, Point Abino sand hills, and Marcy's Woods Port Colborne and Fort Erie
Terrace Lane, Crystal Beach (#255_33) Fort Erie
Bertie Township/Fort Erie:Yacht Harbour Road (#255_34), Ridgeway, beach access points at Burleigh Road (#255_35), Bernard Ave. (#255_36), Colony Road (#255_37), and Windmill Point Road (#255_38), Stone Mill Road, Bertie Bay Road Allowance (#255_39), and beach accesses at Rose Hill Road (#255_40) and Buffalo Road/Crescent Beach (#255_41)
Kraft Drain Mouth (#255_42)
Erie Beach/Waverly Beach Park (#255_43)
Navy Island Niagara Falls

CA=Conservation Authority, NCC=Nature Conservancy of Canada; PP=Provincial Park; RM=Regional Municipality

In Canada, the Common Hoptree is limited to extreme southwestern Ontario by climate, growing degree days, and its specialized habitat requirements. The small Canadian population has a restricted area of occupancy (only 7.5 km2), focussed almost entirely along the sandy, well-drained, often xeric[6], disturbed shorelines of Lake Erie (Ambrose 2002). There, it occurs along the leading edge of woody shoreline vegetation, most often in thickets intervening between the beach grass and/or savanna communities and the dry woodland edges, where it is found less frequently (Ambrose et al. 1985, Ambrose 2002, Jalava et al. 2008). On Pelee and Middle Islands, it also grows on limestone-based substrates, including alvars[7] on the former, as well as in the lake-bottom clays and clay-loams of Pelee Island drainage ditches (Ambrose 2002). The hoptree is shade intolerant, showing a significant reduction or absence of flowering and fruiting even in partial shade (Ambrose et al. 1985). Established seedlings can and need to withstand high soil temperatures, high evaporation, drought, low soil nutrients and sand instability (McLeod and Murphy 1983). Flowers require insect-pollination (Ambrose et al. 1985). The samaras or winged fruit may be dispersed by wind, water, or ice rafting. However, seeds tend to establish under or near existing trees and, as such, much apparently suitable habitat remains unoccupied (Ambrose et al. 1985).


1 Ambrose (2002) reported a scarcity of very large individuals and surmised a high turnover within populations.

2Deciduous trees shed their leaves each year.

3 In dioecious plants, male and female flowers are found on separate individuals.

4 An extirpated designation means that the species has been confirmed to no longer exist at a site.

5 An historic designation means the species is previously known from the site, but has not been verified within the last 20 years.

6 Xeric plants require only a small amount of moisture.

7 In the Great Lakes basin, "alvar" refers to naturally open areas with shallow soils over relatively flat, limestone bedrock, with trees absent or at least not forming a continuous canopy (Reschke et al. 1999, Brownell and Riley 2000).

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