Two forests that used to cover this ridge
Before subdivision, the deep shale soils along the North Shore ridge carried Blue Gum High Forest — a tall wet sclerophyll forest of Sydney blue gum, blackbutt and turpentine, with a lush understorey. It was some of the most productive forest around Sydney, which is exactly why it was cleared first.
What survives is a tiny fraction of the original extent, in scattered remnants. Dalrymple-Hay Nature Reserve at St Ives is the best-known. Both that community and Sydney Turpentine-Ironbark Forest, which occupies the shale-sandstone transition through Ryde, Lane Cove and the lower slopes at Pymble, are listed as critically endangered.
Why this matters to a private owner
Because the remnants are not all in reserves. Individual trees and small stands survive in back gardens across Gordon, Pymble, St Ives, Killara and Turramurra, on blocks that were built around them in the 1920s and 1950s.
A tree that forms part of a listed endangered ecological community attracts protection over and above the ordinary council tree controls. In practice that means applications to remove are assessed far more strictly, refusals are common, and unauthorised removal is treated much more seriously.
How to recognise the species
Sydney blue gum has a smooth blue-grey to white trunk shedding in long ribbons, often with a short rough stocking at the base, and grows tall and straight. Blackbutt has a distinctive rough, dark, fissured bark on the lower trunk — the "black butt" — with smooth white bark above. Turpentine has persistent, deeply furrowed reddish-brown bark all the way up and leaves with a distinctly pale, hairy underside.
Those three growing together on deep shale soil, forty metres tall, with a native shrub layer underneath, is what a remnant looks like.
Living with a protected tree
This is where most owners end up, and it is more workable than it sounds. The real risk from a mature eucalypt is falling deadwood and over-extended limbs, not the trunk. Regular inspection, deadwood removal and targeted clearance from the roofline handles that, and generally sits within what councils permit without a full application.
What does not work is topping. Cutting a mature blue gum back to stubs produces a mass of weakly attached regrowth that is more hazardous within a few years, and on a protected tree it is an offence as well as bad practice. The pruning page explains the alternative.
Green waste and the back fence
One more thing worth saying. Dumping garden waste over a back fence into an adjoining bushland reserve introduces weeds and nutrients into exactly the remnants that are left. Councils across the North Shore pursue it. Green waste from any job we quote leaves with the truck.
Ring (02) 9090 4915 to have a tree assessed. See also the St Ives and Pymble pages, and the rest of the blog.
Frequently asked questions
How do I know if my trees are part of a remnant?
It is a judgement about species mix, soil and site history rather than a single tree. Tall Sydney blue gum, blackbutt and turpentine growing together on deep shale soil with a native understorey is a strong indicator. Councils hold mapping, and a consulting arborist or ecologist can assess it properly. Do not decide from the footpath.
Does an endangered listing mean I can never remove the tree?
Not never, but the bar is high and the process is longer. A tree with a genuine structural failure can still be dealt with, supported by proper assessment. What will not succeed is an application based on leaf drop, shade, height or a view. Management rather than removal is the realistic expectation.