Removing buckthorn and planting the ravine for wildlife
In 2008, we were lucky to receive a Green Partnership Program grant from the City of Ottawa to remove buckthorn trees from the ravine that runs through the FWG. The grant also covered replanting with native trees and shrubs.
- Buckthorn is not a native species.
- Buckthorn tends to grow thickly around the base of trees that birds use frequently (apple, hawthorn, etc.), its many saplings may suppress the growth of these more desirable trees, and they will prevent native shrubs from growing near these trees.
- Leaving even one berry-producing buckthorn tree means that we would continue having new buckthorn seedlings throughout the garden as birds eat the berries and spread the seeds (i.e., we’d be making more work over an indefinite period).
- We have an obligation to remove invasives as much as possible to prevent their spread to other parts of the city and region.
With its layers of trees and shrubs of all sizes, the ravine is a perfect home for birds, mammals, and other wildlife at the FWG.
The ravine is a valued part of the FWG as it is used by many, many wildlife species. It is sheltered from winter winds and the variety of trees and shrubs keep the area cool in summer. A stream runs along the bottom all year. Thus, the ravine provides all the elements of a good wildlife garden: food, water, shelter, and nest sites.
Unfortunately, the ravine also contains several large buckthorn trees; these are self-seeding and creating dense thickets that are slowly replacing other needed vegetation and, thus, reducing diversity.
The ravine is a difficult area for volunteers to work. Cutting large trees with hand saws while standing on a slope, then painstakingly piling branches out of the way is grueling work. Applying for a grant through the City of Ottawa’s Green Partnership Program allowed us to hire people with the appropriate equipment to do this job efficiently and quickly.
A winch was used to pull out smaller trees, roots and all. Larger trees were cut and branches hauled out of the ravine.
One issue was timing of this work as we wanted to cause the minimum disturbance to wildlife. From April to July birds are nesting; by September, mammals are collecting their winter food supply. As a result, the heavy work (using machinery) was done in mid-August.
E&S Tree Service employees removed at least 13 very large buckthorn trees and innumerable smaller ones from half of the south slope of the ravine. Some were pulled from the roots with a winch and larger ones were chain-sawed down to soil level.
You can see from the size of this stump (left) how massive the buckthorn trees were with their tangle of multiple trunks.
To prevent regrowth, Tony cuts stumps off at ground level…
and covers them with thick pool liner.
The removed trees were chipped and the chips were exchanged for chips of non-invasive tree species. The exchange was made so that we wouldn’t be spreading buckthorn seeds around our site. Some of the chips have been used as mulch around the trails and garden, with plenty more available for next season.
An industrial chipper made short work of the berry-laden branches.
Several large brush piles were built around and within the cleared area to block access, slow erosion, and provide wildlife cover.
The brushpiles were more visible after snowfall.
The work also involved mowing down and pulling nodes of the invasive alien dog-strangling vine from large areas of the slope and access areas.
Native plant remediation
Once the choking canopy of buckthorn and dog-strangling vine was removed, we discovered several good clumps of native shrubs valuable to wildlife, including hawthorn trees, red osier dogwood, wild grape, and wild plum trees.
Although the bare slope looked like a bit of a wasteland this fall, the purple flowering raspberry, red osier dogwood and other species already growing at the edges will quickly spread into the open space. FWG volunteers also planted many new native trees and shrubs in this area.
In addition, 52 native trees and shrubs were planted in the cleared area: five canopy trees (including white ash, white oak, and white birch) and many shrubs (especially red osier dogwood and rowan berry for initial erosion control). Mulch and tarpaulins cover other sections of the slope ready for more understorey plantings next season.
The volunteers who planted the shrubs and trees were encouraged to dig into the slope to make a level area in which to plant the new saplings. Soil was built up along the front to form sort of a dish around the trunk so that water would be held near it instead of running down the slope. Branches found on the slope were placed perpendicular to the direction of the slope for the same reason and to prevent erosion.
In the next seasons, we intend to follow up by comparing the effectiveness of this clearance with winch and tree crew versus an earlier slope clearance done painstakingly by hand.
Thanks for all the hard work
Tony Denton (left), who has been carefully clearly buckthorn from the FWG for many years and has developed many effective techniques and strategies, was very thankful to have this help from professionals with heavy equipment.
Elizabeth Gammell (left) handled the grant application, the many permissions and inspections that were necessary before work could begin, coordination of work, and follow-up reports.
In addition to Elizabeth and Tony, we also thank Iola Price who helped immensely with the paperwork for this project and making sure everyone knew what was happening when. She was a co-applicant representing the Rockcliffe Park Residents Association who also benefited from buckthorn removal around community buildings. Iola’s experience and advice were invaluable.
Finally, many of the FWG volunteers from our Friday crew replanted the cleared space. This was very hard and hot work. We even installed a rope to help volunteers haul themselves back up the steep slope to fetch water and tools. A big thanks to all who helped with this important step.
Photos were taken by Tony Denton, Iola Price, and Charlie Clifford. Thanks very much for this visual record of the work.
2009 – phase 2
In June, Price WaterhouseCoopers volunteers once again offered to help out with a day of hard work at the FWG. This seemed like a good opportunity to tackle replanting the ravine, so we ordered three dozen white cedars from Ferguson Forest for the occasion.
Undaunted as always, the PWC Green Team (left) scrambled up and down the steep slope of the ravine with shovels, trees, mulch, and water. And they actually seemed to enjoy the hard work. What a team!
Several of our Friday volunteers worked with the group, including Tremayne Stanton-Kennedy, who showed us how to make “fascines” – bundles of twigs and brush that are tied together, then fastened to the ground below the newly planted trees. (See, for example, the Ohio Stream Management Guide.) We installed as many of these bundles as we could make to prevent erosion on the still-bare slope.
All the cedars were planted in four groups. We’re trying to keep them watered (not difficult this summer) and hope that they will soon fill in and form good winter cover for wildlife.
Renate and Tremayne are continuing the ravine rehabilitation work, preventing regrowth of buckthorn stumps and encouraging the native shrubs, trees, and wildflowers we’re planting.
2012 – phase 3
In spring 2012, we were fortunate to be able to continue this project when Microsoft and the Evergreen Foundation partnered for a tree-planting day at the FWG. A generous grant allowed us to buy 100 larger trees and shrubs as well as small saplings.
See our newsletter report: Planting in the ravine
The cedars planted in 2009 continue to flourish. However, the May 2012 planting was followed by a month of very dry weather and the trees struggled to survive. We watered as often as possible and were provided with a dozen tree bags from the city. We are hoping these efforts pay off and are waiting to see how many trees will leaf out this spring (2013).