Succession – the arboreal kind

By Jennifer Humphries

Whether or not you are a fan of the Succession series, there is a kind of succession that matters to our neighbourhood – the kind that keeps our streets and backyards leafy green.

Over the past few months, the Environment Committee of the Glebe Community Association (GCA) has been encouraging residents to plant new trees and protect the ones they have. The eco-role of trees is well known, and there is increasing awareness of their positive contribution to mental and physical health.

We’ve created a map showing tree canopy gaps, and we’ll soon be canvassing blocks where more than 40 per cent of front yards lack a tree. Take a look at the map, and if your block is in the red or yellow, please consider getting in touch with us at environment@ glebeca.ca. Glebe Annex and Dow’s Lake Area are not yet on our map; we hope to add them in the coming months.

Succession planning

We estimate that more than half of the trees in the Glebe are 80-plus years old. The lifespan of a tree can reach well over 100 years, but our trees face the usual city challenges of salt and dog urine as well as an increasing number of massive weather events – think ice storms, derechos and the flood-anddrought seesaw. Many of the elders will be gone within a decade or two. Successor tree planting ensures that we will still have canopy when that happens.

Andrew Boyd, a professional forester and consultant for The IFS Group, answered my questions about successor planting. I hope you find this information as useful as I do. And for more tree selection information, Boyd recommends going to a reputable source such as the Morton Arboretum (mortonarb.org/).

Succession Planting Q and A with Andrew Boyd

I want to plant a new tree in my yard while my mature tree is still healthy, so that when the mature tree dies or is removed, I will have a younger successor tree ready to take its place.

1. How far from the older tree should I plant?

There’s no hard and fast rule about distance. Every tree has a shade tolerance, so if your big tree has a thick canopy, look for a tree such as a red maple that can tolerate shade. And even though trees are used to sharing below-ground space, make sure the new tree has a reasonable amount of room for roots. Also, since the older tree will eventually have to be removed, consider how a company could access it without impacting the successor tree.

2. How big a concern are pipes?

Won’t a tree’s roots work around them? Can the roots really puncture a pipe?

Tree roots won’t puncture a pipe. If a pipe is leaking water, though, roots will grow towards the water. The City of Ottawa uses copper for its water mains and pipes; these are designed not to break or leak. If you have old lead pipes, there is a city program that can advise and offers a loan to make the switch to copper.

3. How big a concern are wires? I understand that communications wires are not as big an issue as electrical wires. Why is that?

Communications wires such as those of Bell Canada are less of a concern, though it is a good idea to prune if branches seem likely to bring a wire down (communications companies do not prune). On the contrary, Hydro Ottawa prunes and often in such a way to disfigure a tree and, by making it asymmetrical and moving its centre of gravity, weaken it. If there are electrical wires overhead it’s best to choose a smaller tree, or to plant as far as possible away from them.

4. Is the species a consideration?

All species are possible, bearing in mind shade tolerance. Another consideration: there are a few species that produce substances that are toxic to other plants and trees. This includes the highly valuable black walnut –good to plant but possibly not alongside your mature tree of another species.

5. With extreme weather events increasing in frequency, are there trees that are more likely to withstand drought, windstorms, etc.?

A recent article from the International Society of Arboriculture recommends the oak as the tree least

Annual General Meeting

Tuesday, June 13, 2023, 7:00 p.m.

In person at the Glebe Community Centre

Neighbours, you are invited to join us for our Annual General Meeting (AGM) where you will hear all about our activities in 2022-23 and GCA members will vote for the Board of Directors for 2023-2024.