The surprising thing about pruning is how much volume a small amount of plant produces. Cutting thirty centimetres off eighteen metres of hedge removes about twelve cubic metres of envelope, and the pile that results is around seven — because branches are mostly air, and a pile of them is more air still. That is three or four times what anyone expects from looking at the hedge, and it is why a job that seemed like a morning’s work ends with a pile that fills a trailer. This sizes the pile, converts it into bags or bins, and shows what a chipper turns it into.
Hedge, cut and disposal
A hedge cut produces a pile several times the size of the material in it.
Depth off the top and the sides. 0.3 m is a hard cut; 0.1 m is a trim.
Branchy material piled loosely is about 60% of its envelope; leafier, less.
A garden waste bag or wheelie bin is commonly 240 L.
Result
Why branches are mostly air
A hedge is a solid-looking object that is, in volume terms, largely gaps. Cutting thirty centimetres off the top and the sides of eighteen metres of it removes an envelope of about twelve cubic metres, and the material in that envelope — the actual wood and leaf — occupies a fraction of it. Piled, it occupies about sixty percent of the envelope, because piling adds new gaps between the branches.
That sixty percent is the number that catches people out, and it moves with the material. Woody prunings from a shrub pile loosely and sit near sixty percent. Leafy, soft growth compacts and sits nearer thirty. Fresh green growth is heavier per cubic metre than dry woody material, because of the water in it — a pile of green hedge clippings can weigh twice what the same pile weighs after a fortnight of drying.
Disposal is the real job
Cutting the hedge is the part people plan for. Moving the material is the part that takes the afternoon, and it is the part that decides how the job is done. Seven cubic metres is thirty filled bags, or five trailer loads, or one visit from a grab lorry — and thirty bags is a genuinely long afternoon with a barrow and a bag.
The options in order of effort are: chip it and keep it, take it to a green waste facility by trailer, use a council collection if there is one, or hire a skip. Chipping and keeping it is by far the best outcome where there is anywhere to put the mulch, because it turns a disposal cost into a material you would otherwise buy.
In most places it is an offence to cut a hedge during the bird nesting season, which typically runs from March to August, if there are birds nesting in it.
Cut outside that window, or check carefully before you start. A hedge in full leaf hides a nest completely.
Chipping changes the arithmetic completely
A chipper reduces woody material to roughly a quarter of its piled volume, and it turns it into something worth having. Seven cubic metres of hedge becomes under two cubic metres of chip, which is a mulch that would cost real money to buy and that goes straight onto the beds it came from.
The catches are noise, cost and what the chipper will take. Hiring a machine for a day is reasonable, and it makes sense for a hedge of any size; buying one only makes sense with a lot of woody material every year. Most hired machines have a maximum branch diameter of around 40 to 75 millimetres, so thick stems have to be cut out and dealt with separately.
| Material | Best route | Volume out | Note |
|---|---|---|---|
| Soft hedge clippings | Compost heap | 40% | Mix with browns or it goes slimy |
| Woody shrub prunings | Chipper | 25% | Best outcome: mulch |
| Thick stems over 75 mm | Firewood or tip | 100% | Chippers will not take them |
| Ivy and bindweed | Tip, not compost | 100% | It will regrow from the heap |
| Diseased material | Tip or burn | 3 to 100% | Do not compost it |
| Conifer clippings | Chipper or tip | 25% | Slow to break down |
A worked example
- EnvelopeEighteen metres by 2.2 metres by 0.3 metres is 11.88 m³ of hedge.
- PiledAt sixty percent density the pile is about 7.13 m³.
- BagsThat is 7,128 litres, or 30 bags of 240 litres — at $4 each, $120 to dispose of.
- Or chippedThrough a chipper the same material becomes about 1.78 m³ of mulch, worth roughly what the disposal would have cost.
- Or loadedUntreated, it is 5 trailer loads at 1.5 m³ each.
A hundred and twenty dollars of disposal against a couple of cubic metres of free mulch is the whole argument for hiring a chipper for the day, and it gets stronger the bigger the hedge.
Timing, tools and aftercare
Cut hedges in late winter or early spring, before the nesting season and while the structure is visible. Evergreens are better cut in late summer or early autumn, when growth has slowed but there is still time to heal before cold weather. Avoid cutting in a hard frost, which blackens the cut ends.
Use the right tool: shears or a hedgetrimmer for soft annual growth, loppers and a saw for anything thicker than about 20 millimetres, because tearing woody stems with a trimmer leaves ragged cuts that die back. Cut with a slight batter — wider at the bottom than the top — so the lower growth is not shaded out by the top.
Clear the base before you start, because finding the bottom of the hedge under a season of clippings is how cuts end up uneven. Where the clippings are being composted rather than chipped, the compost bin figure says whether there is room, and the haulage figure sizes the trip if they are not. The mulch figure is what the chipped output is worth putting on.
Do
- Cut outside the nesting season, or check first.
- Use loppers or a saw on anything thicker than about 20 mm.
- Chip woody material and keep the mulch rather than paying to remove it.
- Cut with a slight batter, wider at the bottom.
- Clear the base before starting so the cut line is visible.
Avoid
- Cutting in the nesting season without checking.
- Tearing woody stems with a trimmer, which leaves them to die back.
- Composting ivy, bindweed or anything diseased.
- Underestimating the pile and running out of bags.
- Cutting in a hard frost, which blackens the cut ends.
Where the numbers stop being true
The sixty-percent pile density is a general figure for branchy material. Very leafy clippings compact to nearer thirty percent; straight, woody prunings stack densely and stay nearer eighty. If the material is of one kind, adjust it; if it is mixed, sixty is reasonable.
The envelope calculation assumes the cut is uniform over the whole face of the hedge. Reducing the height by thirty centimetres and the sides by ten is two different volumes, and it is worth running them separately if they differ much.
Nothing here accounts for water. Fresh clippings carry a lot of it, and a pile that weighs a tonne when cut weighs half that after a fortnight of dry weather — which matters for a trailer's weight limit far more than for its volume.
How the figures are produced
The envelope is length times height times the depth being cut off. The pile volume is that times the density percentage, which accounts for the air between the branches and the air in the pile. Bags are pile litres divided by bag size, rounded up, and trailer loads use 1.5 cubic metres. Chipped volume is twenty-five percent of the pile, which is the typical reduction for woody material through a chipper.
Questions people ask
Why is the pile so much bigger than I expected?
Because a hedge is mostly gaps, and cutting a face off it creates a pile that is mostly gaps too. An 18 m hedge cut back by 30 cm makes about seven cubic metres.
How many bags will it fill?
About thirty bags of 240 litres for seven cubic metres. It is a long afternoon.
Is chipping worth hiring a machine for?
For a hedge of any size, yes: it turns a disposal cost into mulch you would otherwise buy, and it removes four fifths of the volume.
When can I cut a hedge?
Outside the nesting season, which is generally March to August. Late winter for deciduous, late summer for evergreen.
Can I compost hedge clippings?
Soft growth yes, mixed with dry browns. Woody material takes years unless it is chipped first.
What should not be composted?
Ivy, bindweed, anything with running roots or viable seed, and anything diseased. Those leave the garden.