Why Trees Die after Construction

 Here's a few interesting casualties that manifested this spring...

I am not a certified arborist, so these are observations from experience and my apprenticeship courses at Kwantlen and general research (the UBC Botanical Garden forum is a good source).

This first photo is of a Cypress spp. that showed stress early this spring and looked like this by June. The owner (a neighbour to one of my clients) raced over to get my (free) diagnosis en route to an appointment.

I noted that the interlocking-paver driveway, installed with the house reno/reconstruction five years ago, had probably removed the rootzone critical to the tree's survival. It was already marooned in a narrow space next to the road, and trees can take a surprisingly long time to die, as they draw on dwindling resources.

There is evidence of cypress tip moth on the branches (next photo) but these little critters only attack stressed trees. The cypress behind this one is fine--so another factor (excavated rootzone...?) had to weaken the tree first.

 The next photo (right) is of the trunks of a mature Arbutus unedo/strawberry tree hedge, buried in a temporary gravel access path installed on a construction site next to another one of my gardens. Several pines and a hardy hibiscus were also buried in the construction landslide from next door!

When I called the construction company to complain, they called back immediately with profuse apologies and removed the gravel the next week, building a temporary retaining wall to keep it on the property line. Nevertheless, the gravel had already been in place for at least a month. If the soil was compacted too much in that time, the plant roots won't get enough air/water/etc. and the plants could start to fail sometime in the future. The company has assured me they will pay for any damages...but if I hadn't called they would have simply got away with it. When construction companies jump, you know they're doing something they darn well know they shouldn't be doing.

The last photo is of a formerly lovely and mature Arbutus menziesii specimen on the same street--also on a site that underwent major construction about five years ago. The problem here is that the wild genus of Arbutus cannot handle rootzone disturbance of any kind. These trees naturally grow out of oceanside bluffs, or seed in the driest of understories, and defy any measure of cultivation. On this site, well-meaning designers installed an irrigated garden bed around the base of the tree with this result...several years later.

So the moral of the story here is if a tree is in massive failure or clearly dead, the cause may be traced to changes in the rootzone during and after construction.