By Jeff Tribe

The Arboretum’s Elm Recovery Project (ERP) is striving to return a foundational Ontario species from trees which merely survive, to majestic 200-year-old icons which fully thrive.
“These are giants in our landscape we are missing,” said Alison Morrison, Manager of Horticulture, The Arboretum, University of Guelph.
Historically, white (or American) elm trees were a woodland species also embraced in urban settings for height and a visually-pleasing hourglass shape. Valuable as a heat source, those who have cut and hand-split elm will also recognize a true hard wood with a twisty grain.
Ontario elms sharply declined in separate waves of Dutch Elm Disease (DED), a fungal infection carried on the backs of native elm bark beetles and European elm bark beetles.
Holland may get a bad rap in the disease’s nomenclature, says Morrison, clarifying that the country wasn’t host to “patient zero”, rather a nation which first identified the disease.
Elm trees’ response to DED is to try and isolate its impact. A tree blocks off infected limbs, says Morrison, hoping to compartmentalize and limit damage which spreads from limb to limb through an extended period as long as a decade or two.
“Over time the tree shuts itself down.”
The first wave of DED hit Ontario in the 1940s, says Morrison, a second in the 1960s and ’70s. Countermeasures were put in place including a ban on transporting potentially-infected elm. Panicked response also included creating “firebreaks” which removed many elms and was ultimately unsuccessful with the added destruction of a wide swath of potentially-valuable genetics.
The ERP was initiated 26 years ago in 1998 by Arboretum Interpretive Horticulturalist Henry Kock whose concern for the species’ decline also recognized there were mature survivors.
“But they were too segmented for a viable self-sustaining population,” said Morrison.
The roadmap to creating long-term elm viability included treating trees combined with a breeding program based on disease-resistant genetics. It is hoped that eventually, offspring from carefully-selected resistant stock can be replanted throughout the province. Apart from their own presence, their pollen may reinforce resistance and survivability of existing surrounding trees and encourage accelerated recovery.
Ironically, ash trees replaced diseased and dying elms, only to be devastated in turn by the emerald ash borer. The emerald borer can breed in saplings as thin in width as a pencil, challenging recovery.
Elms are self-sustaining to a degree, given they breed at around 12 years of age and up, and can survive 35 to 50 years with DED. The ERP seeks a return to full, 200-year-old maturity “to whatever degree is practical,” says Morrison.
Arboretum staff received 900 responses to a well-publicized call-out for survivors, visited 600 sites, with around 300 trees eventually being selected. Consciously, the selection process was not simplified to “A+” trees, rather a range of survivors ranked as low as ‘“D”, in order to retain broader genetic diversity. A+ trees may be highly-resistant to DED explains Morrison, however they might also have been weak in resistance to another disease or condition which could arise. Keeping a range including a “C-” for example, may prove valuable in carrying a broader gene pool forward.
“In the grand scheme of things, this program is still in its infancy,” Morrison explained. “We don’t know what else they’re resistant to and what else they’re susceptible to.”
Cuttings were taken off the selected survivors, an approach maintaining greater consistency of genetics in offspring as opposed to seed-based propagation. The cuttings were grafted onto local elm rootstock.
Eighty of the original 300 trees in the initial ERP orchard survive in a cross-pollinating location near The Arboretum’s Hilton Centre. A second plantation, several hundred metres further to the north, currently has around 40 of a planned 80 individuals, established on a more generously-spaced grid.
“It has worked,” says Morrison, citing benefits including a living, disease-tolerant archive which would not have existed, as well as extensive research around that 26-year exercise.
The ERP may be one of the higher-profile programs overseen through The Arboretum, however it’s far from the lone initiative. The 400-acre site boasts the largest collection of native Ontario woody plants, and is home to some form of conservation support for over 30 rare or endangered species, including for example, the red mulberry recovery project. Challenges will continue to arise, be that DED, oak wilt or the presence of the woolly adelgid, an East Asian invasive insect whose lack of natural predators threatens the eastern and Carolina hemlock.
In response, research leading to solutions can be crucial for not only affected plant and insect life, but impact on humans, says Morrison. “It’s a constant negotiation between nature and ourselves.”
“Our survival is intricately aligned with the survival of nature, period,” added Arboretum Director Justine Richardson. “Health, well-being, clean air, clean water is essential.”
An ERP borne out of one individual’s observations, converted to action, has grown to involve a team of dedicated researchers, volunteers and landowners. The team is currently identifying forward-thinking strategic planning.
“With enough time and commitment, it works,” Morrison concluded. “I don’t think it’s easy and it’s not quick - but that time and energy is well spent.”
BUTTERNUT RECOVERY
A cooperative program including the Forest Gene Conservation Association (FGCA) and the Upper Thames River Conservation Authority (UTRCA) is striving to aid the butternut tree’s recovery from butternut canker.
A “masting” tree environmentally valuable for the edible nuts and habitat it provides, the relatively short-lived species has been seriously affected by the fungal disease. The UTRCA’s efforts to support butternut recovery began in 1992, subsequently dovetailing into a program relatable in some aspects to the ERP. 
The FGCA has sourced a total of 175 parent trees, says that organization’s Director of Species Conservation Heather Zurbigg, but is always open to more canker-tolerant butternuts. The FGCA is especially interested in resistant trees from among others which have been seriously affected, indicating that despite a high prevalence of canker, they have demonstrated the ability to survive.
Licensed arborists were contracted to collect scions from canker-resistant trees which were grafted onto root stock. The UTRCA’s first grafted combinations were planted in 2015 in a managed, protected orchard or archive near Woodstock.
FGCA is involved in six archives, says Zurbigg, two each in southwestern, central and eastern Ontario.
“We’re getting there,” said Rob Davies, Forestry and Restoration Supervisor with the UTRCA, noting 1,200 seeds were collected last year. The resultant seedlings will be planted in UTRCA reforestation projects and monitored to see if resistance has been successfully passed on.
Landowners with either tolerant trees or the space to plant and monitor program offspring are invited to email nina@fgca.net for more information.
There is no guarantee, but Davies says American experience, which he considers in advance of ours in Canada, has proven the effort can be successful.
“At least we’re doing something to get this species back in the landscape.” ◊