As west side portions of the Confederation Line advance in construction, more fall landscaping is going in, like these trees planted on the north side of Bayview Station:
I vaguely recall that the terms of the NCC lending the rail corridor to the City was that 200 trees had to be planted between the tunnel portal and Bayview. It did not specify how many had to survive.
When I see trees planted like this I am reminded of volcanoes.
Planting trees too deep is a frequent cause of subsequent demise. It looks like that shouldn’t be a problem here:
Some trees planted during the September late season heatwave had a hard first few days:
From the pathway on the north side of the station, here is a view upslope towards the future station. The Track and Station are about 21′ above ground level. The slope itself is made of carefully selected gravel and stone materials, packed down hard with heavy roller equipment. Much of this was put in place for the original transitway, but significant regrading and new materials have been added. The material has been engineered to drain quickly and thoroughly, as soggy slopes might have freeze-thaw cycles and eventual erosion that would affect the tracks on the top of the slope.
A few inches of topsoil has been added on top of the drainage layer, and shallow holes are made into which trees are put:
As you can see from the photo below, the hole is shallow. But it is wide enough that a few bushels of topsoil is added around the root ball:
Subsequent rainfalls and the occasional animal or human clambering over the slope would cause erosion. At the steepest portion of the slope, peastone (round gravel) is put down over a bed of landscape fabric to prevent weeds from growing up through it. Earlier station designs which included drainage ponds with surface runoff and water loving plants seem to have been valued out in favour of large catchbasins feeding water into the sewers.
The rest of the slope was generously planted in assorted shrubs, in large clusters. These will, when larger, shade the soil so it doesn’t dry out so instantly, and will help diffuse rainfall so it has time to be absorbed into the topsoil or percolate straight down through the 21′ vertical depth of drainage bed. Until they can become established, a layer of moisture-holding and shading mulch is spread over the topsoil after the plants are placed.
I place most of my hopes on the sumac, which is capable of growing on the steeply engineered slopes of stone everywhere else along the transitway. It’s tough. It’s pretty. It’s dense. And it’s capable of creating a rich soil layer trees will thrive in, given a hundred years or so.
I have no doubt that some of the trees will survive the first year. Those that don’t, will be replaced by the contractor (the cost being built into the contract) usually with a smaller caliper replacement tree. If that dies, no one will probably notice. The contractor will water the trees for the first two years.
Trees planted in similar rocky soil along the Trillium pathway had a mixed survival rate, but suffered badly in the late summer / fall drought last year. Fortunately community pressure on the City succeeded in getting some extra watering truck runs in along the pathway. A bunch also died from rabbits and mice knawing on the bark (the city requires a bark protector for two years, after which almost all of them disappear; the NCC trees somehow kept their bark protectors for several more years). On the south side of the Bayview Trillium Station there are a number of large-ish transplanted trees that have dried out or otherwise failed to thrive.
Along our residential streets, or in parks, I think that trees planted fairly shallowly, with a modest bit of backfilling with topsoil, have a reasonable chance, if lucky, to survive and grow their roots under the surrounding lawns and become established. But I am less confident when the same standards are used for trees planted on top of a 21′ deep drainage bed. An Ottawa landscape architect assures me that the trees have enough soil to hold moisture for “an average Ottawa month”.
I asked what might happen if there was a drought, which seem reasonably common in August or September in recent years. After all, the average isn’t of much use if every so often there is a four week drought and all the trees die. “Ahh” he replied, “we follow the tables and charts and rules and the terms of the contract…”
Meanwhile, there is the area northwest of the station which I hope will be planted soon.
The landscape architects also specified a really cute stone and plant and tree garden right between the Albert overpass and the Confederation overpass. It looks great from pathway level, but from the bridge I am immediately struck by the amount of salt that is going to rain down on these trees every winter. Alas, they are maple trees, not especially salt hardy, whereas something like Siberian Olives are Halophytic or so salt proof they thrive along the Queensway slopes.