The rule that governs everything
Conifers are not broadleaf trees and they do not respond to pruning like them.
A eucalypt cut back hard will push epicormic shoots from dormant buds under the bark. It may not be good for the tree, but it will regrow. Most cedars, cypresses, junipers and related conifers will not. They have very few dormant buds in old wood, so a cut made back into the bare interior stays bare for the life of the tree.
Everything else about pruning a cedar follows from that.
Rule one: stay in the green
Before any cut, part the foliage and find where the green needles stop and bare brown wood begins. That boundary is your limit.
Cut within the green and the plant responds by thickening. Cut past it and you have made a permanent hole. On a hedge that hole never fills. On a specimen tree it stays visible from every angle.
Rule two: never remove the leader
Cedars have a single dominant vertical leader and a whorled branch structure that depends on it. Remove the leader to control height and several side branches compete to replace it, producing a forked, weakly attached top and a permanently distorted form.
If a conifer has outgrown its position, that is a planting mistake rather than a pruning problem, and removal plus a better replacement is the honest fix.
The same logic applies to Norfolk Island pines, which are everywhere along the Caloundra and Sunshine Coast foreshore.
Rule three: little and often
Light annual trimming keeps a cedar dense and keeps every cut inside the green. Neglect it for five years and the only way to reduce it is to cut into bare wood, which you cannot do.
This is why hedged conifers need a consistent regime rather than an occasional heavy cut.
Rule four: dead and diseased material comes out
Interior dieback from shading is normal and does not need removing. Whole dead branches, storm damage and anything showing canker or fungal infection should come out, cutting back to healthy wood or to the point of origin.
In the Sunshine Coast's humidity, conifers in poorly ventilated positions are prone to fungal problems. Thinning to improve airflow is legitimate and useful - but again, only within the green.
Rule five: get the timing right
Late winter into early spring, before the new flush. A light tidy in early summer once the first flush has hardened is fine.
Avoid the hottest part of summer, because interior foliage suddenly exposed to direct sun will scorch. Avoid prolonged wet weather, when spores colonise fresh cuts fastest. The general timing guide covers the local calendar.
Tools
Secateurs and hand shears for foliage. A pruning saw for whole branches. Powered hedgers are fine on a formal hedge and wrong on a specimen tree, because they cut through whatever is in front of them and leave shredded needle ends that brown off.
Sap is resinous and gums blades quickly - clean them as you go. General technique applies too.
For a conifer that has already been cut too hard, ring (07) 5408 6029 and get an honest assessment of whether it is worth keeping.
Frequently asked questions
Will a cedar grow back if I cut it hard?
Usually not. Most cedars and related conifers have a dead zone of bare brown wood inside the green foliage, and they have very few dormant buds there. Cut back into it and that section stays bare permanently. This is the single most important difference between conifers and broadleaf trees for pruning purposes.
When should cedars be pruned?
Late winter into early spring, before the new growth flush. Light shaping can be done in early summer once the first flush has hardened. Avoid pruning in the hottest part of summer, when freshly exposed interior foliage will scorch, and avoid it in prolonged wet weather when fungal problems spread fastest.
Can I reduce the height of a cedar?
Only marginally, and not by removing the leader. Cedars and most conifers have a single dominant leader and a structure that depends on it. Cut it off and the tree loses its form permanently, and the competing leaders that replace it are weakly attached. If a conifer is too tall for its position, removal and replanting is the honest answer.
What is the brown dead patch inside my cedar?
Normal. Interior foliage that no longer receives light dies off naturally, leaving a shell of green on the outside and bare wood within. It is not a disease. It does mean your pruning has to stay within the green - anything cut back past it will not refoliate.