The gum at the back of a Castle Hill block has grown well past the roofline. The lilly pilly planted as a screen in a Kellyville estate is taller than the second storey. Someone has offered to "just take the top out". It sounds sensible. It's a job we won't arrange, and the reason has nothing to do with being fussy.
What topping actually is
Topping, or lopping, means cutting the main stems of a tree back to a set height, regardless of where the branches join. The cuts land wherever the saw happens to be, usually leaving thick stubs with nothing growing from them.
Good pruning works the other way. Every cut is made at a natural point: back to the branch collar where a limb meets the trunk, or back to a smaller branch that can take over the growth. That's the basis of AS 4373, the Australian standard for pruning amenity trees. All the pruning we arrange is done to it, and that's why topping is off the table.
What happens to a tree after it's topped
A topped tree doesn't stay the height it was cut to. In most cases it responds in a predictable sequence.
- It loses a large share of its leaves in one go. Leaves are how a tree feeds itself. Take most of them and the tree draws on stored energy to replace them fast, which weakens it.
- It throws out a mass of new shoots. These sprout from dormant buds just below each cut, often dozens per stub. Eucalypts are especially good at this. Their epicormic buds sit under the bark ready for exactly this kind of damage, which is why a lopped gum can look like a green broom within a season or two.
- The new shoots are weakly attached. A branch that grows from the trunk normally has wood laid down around its base year after year. Epicormic shoots grow from the outer layers and don't have that anchor. As they get heavy, they're prone to tearing out.
- The stubs start to decay. A large cut with nothing growing from it can't seal over well. Fungi and rot get in and work down into the main stems, often out of sight.
Put those together and the result is a familiar one. The tree grows back to the same height, it's denser than before, and the new limbs sit on top of decaying wood. It's now heavier at the top and weaker underneath. That's a worse tree to have over a roof or a driveway than the one you started with.
Why spring makes it obvious
Spring is when trees in the Hills put on their growth surge. A tree topped in winter often reshoots hard as the weather warms, and by the time summer storms arrive it's carrying a full head of soft new growth on weak attachments. That's exactly the load a southerly buster finds.
It's also why topping has to be repeated. Once a tree has been lopped, the regrowth usually needs cutting again every few years, and each round leaves more stubs and more decay. A tree that was a one-off job becomes a standing cost.
What to ask for instead
Most people asking for a tree to be topped want one of a handful of things: less height, more light, clearance from the roof, or less risk in a storm. Each of those has a proper pruning answer. These are the terms worth knowing when you talk to anyone about tree pruning.
Crown reduction
This lowers the height or spread of a tree by cutting branches back to a smaller branch that can take over as the new tip. The tree keeps its natural shape, just smaller. A common rule of thumb is that the branch you cut back to should be a reasonable fraction of the size of the one you remove, so it can carry the growth. Done properly, a reduction tends to hold its size far longer than a lop.
Not every tree takes a big reduction well. Some species tolerate it; others, and older trees in poor health, don't. A qualified arborist will tell you how much a given tree can lose.
Crown thinning
This removes selected branches through the canopy to let light and wind through, without changing the outline much. It's the usual answer for a dense tree shading a backyard or catching wind like a sail.
Crown lifting
This removes the lower branches to give clearance over a driveway, path, fence or roof. It's common on the narrow side access of older Baulkham Hills and Winston Hills blocks, where a single low limb is the whole problem.
Deadwooding
Dead branches are usually the first thing to come down in a strong wind. Removing them is often the most useful storm-season job you can do on a big gum, and it barely changes how the tree looks.
Clearance pruning
Cutting back specific limbs off a roof, gutter or wall. Note that anything near powerlines is a different matter. Nobody other than an authorised worker should go within 3 metres of them.
When the honest answer is removal
Sometimes a tree has simply outgrown its spot. A blue gum planted on a small block, or a fast-growing screening tree three metres from the house, may need reducing so hard to fit that it can't be done to standard.
In that case, topping it just postpones the problem and makes it more dangerous in the meantime. The better options are usually to accept a properly reduced tree with a bit more height than you'd like, or to remove it and plant something suited to the space. We'd rather tell you that than arrange a job that has to be redone every few years.
Council controls apply to pruning too
People often assume council rules only cover removal. In many areas they also cover pruning, particularly heavy pruning on larger trees. Topping a protected tree can attract the same consequences as removing one. The controls vary by council and by property, and parts of the Hills sit across council boundaries, so check before any significant work. Our page on council tree approval explains how the system generally works.
Questions to ask whoever does the work
If you're getting quotes for pruning, these sort out the arborists from the loppers quickly:
- Do you prune to AS 4373?
- Where will each cut be made: to a branch collar or a smaller branch, or to a set height?
- Roughly how much of the canopy will come off?
- Will the work be done by a qualified arborist (AQF Level 3)?
- Is there public liability insurance, and can I see the certificate?
An answer like "we'll take it down by a third across the top" is a lop, whatever it's called on the quote.
What to do next
If a tree has grown bigger than you want, start with what you're trying to fix: height, light, clearance or storm risk. Then ask for the pruning that targets it. Photos of the whole tree, plus a few of where it meets the house, fence or driveway, are usually enough for a ballpark. Send them through the quote form and a qualified arborist will look at what the tree can sensibly take.