Ulmus rubra – Slippery Elm

Slippery Elm on Riverside Dr south of Hog’s Back Rd.

Slippery Elm is a medium-sized tree, favouring alkaline substrate.  It has a distinctive upright/spreading growth form and large thick-textured leaves with multiple forked veins, often with a pronounced fold along mid-vein.  Buds are large, usually with reddish hairs.  The bark can be scaly (somewhat similar to White Oak) or in long vertical grille-like ridges, greyer than Ulmus americana and its ridges not intersecting. 

Slippery Elm is tolerant of dry uplands and found in understory or scattered in canopy of rich mesic forests (buds often nearly lacking reddish hairs in shade).  Similar-looking to uncommonly cultivated Wych Elm (Ulmus glabra), which lacks reddish-hairs on buds.  Quite visually distinctive compared to very common American Elm (Ulmus americana), which is nevertheless frequently confused with Slippery Elm, especially vigorous saplings which can have rough-hairy leaves.  Slippery Elm’s leading branches often grow for some length at a consistently ascending 45 degree angle vs. the vase-like shape of American Elm.

Slippery Elm Bark on a Mature Tree showing vertical ridging.

Slippery Elm is uncommon in eastern Ontario, but can be locally abundant such as at Reveler Conservation Area and Fitzroy Provincial Park.  At Fitzroy look for a grove of mature trees at the bottom of the waterfall at the start of the Terrace Trail. Scattered mature trees and populations occur throughout our region (see iNaturalist uploads) such as in the Carp Hills.  There is an impressive, mature publicly-accessible tree at Mooney’s Bay (adjacent to Terry Fox Athletic Facility parking lot).  Slippery Elm is commercially important for medicinal bark that soothes the colon.  It freely hybridizes with dissimilar-looking invasive Siberian Elm (Ulmus pumila).

Three Slippery Elms along the Terrace Trail by the water fall at Fitzroy Provincial Park. Note the bark’s reddish-brown, vertical plates.

Here are selected photographs with location coordinates in iNaturalist:

http://www.inaturalist.org/observations/5152262 (Mitch Owens Rd mature specimen, with leaves, mesic)
http://www.inaturalist.org/observations/5145006 (Carlington woods medium specimen, good buds, bark, mesic)
http://www.inaturalist.org/observations/4970485 (Copeland Park mature, dying, mesic)
http://www.inaturalist.org/observations/4884014 (Reveler CA; good example of “taco” leaves, limestone upland)
http://www.inaturalist.org/observations/4883899 (Reveler CA; good example of “taco” leaves, limestone upland)
http://www.inaturalist.org/observations/4866990 (relocated from quarry to park; good example of “taco” leaves, mesic)
http://www.inaturalist.org/observations/3129998 (example of adolescent roadside specimen in early spring, mesic)
http://www.inaturalist.org/observations/3078516 (very large specimen behind church in backyard; good example of growth form and expanding spring buds)
http://www.inaturalist.org/observations/3078357 (medium specimen Carp Hills, opening flowers, rocky upland) 
http://www.inaturalist.org/observations/3078161 (medium specimen Carp Hills, opening flowers, rocky upland)
http://www.inaturalist.org/observations/3077545 (Mitch Owens Rd mature specimen, early spring, mesic)
http://www.inaturalist.org/observations/3076932 (large old specimen at Mooney’s Bay, flowering in late spring)
http://www.inaturalist.org/observations/2938298 (mature triple-trunk tree at Petrie Island, sandbar island)
http://www.inaturalist.org/observations/2846164 (good example of the large leaves, mesic)
http://www.inaturalist.org/observations/2782866 (a couple of adolescent specimens, Reveler, limestone upland)
http://www.inaturalist.org/observations/2782855 (sapling with good view of leaves, Reveler limestone upland) 
http://www.inaturalist.org/observations/2782523 (sapling with good view of leaves, Reveler limestone upland)  
http://www.inaturalist.org/observations/2743028 (Mitch Owens Rd mature specimen, spring with early seed developmentg, mesic)
http://www.inaturalist.org/observations/2736760 (mature specimen, with swelling buds) 
http://www.inaturalist.org/observations/2736710 (good example of twigs, from Mitch Owen Rd mature tree) 
http://www.inaturalist.org/observations/2723458 (mature specimen near Mallorytown, shows growth form and bark)
http://www.inaturalist.org/observations/2723739 (mature tree Copeland Park in winter, mesic; tree was dying in summer 2016)  
http://www.inaturalist.org/observations/2700885 (mature tree NW of Aylmer, showing growth form and leaves gestalt, limestone upland) 
http://www.inaturalist.org/observations/2700848 (young tree NW of Aylmer, showing growth form and leaves)
http://www.inaturalist.org/observations/2700824 (very large tree NW of Aylmer, just starting to die of DED)
http://www.inaturalist.org/observations/2693343 (young tree in parking lot near Kingston)
http://www.inaturalist.org/observations/2690389 (young tree in parking lot near Wolf Grove)
http://www.inaturalist.org/observations/2550261 (young tree NW of Aylmer, showing growth form and bark)
http://www.inaturalist.org/observations/2509264 (very large tree NW of Aylmer, showing growth form and bark)
http://www.inaturalist.org/observations/2511438 (very young tree, showing appearnce of leaves)
 
Ulmus rubra entries in iNaturalist:
 
Slippery Elm Buds in late summer (photo by O. Clarkin).
Slippery Elm leaves showing mid-line fold and multiple vein forking, particularly near the edges (photo by O. Clarkin).
Classic growth form of Slippery Elm in Aylmer, PQ (photo by O. Clarkin).