Woody waste: shredding and composting
Most gardens produce waste such as twigs and branches from the pruning of woody plants. This can be troublesome to dispose of in a way that is kind to the environment and to neighbours. Unlike burning, shredding or composting is the ideal solution, resulting in a usable organic material for the garden.
Timing Any time
Any woody clippings and prunings, stems, twigs, and smaller branches.
Larger branches, tree trunks and stumps which ultimately rot down in the garden.
How to deal with woody waste
Woody waste can be dealt with in a number of ways, depending on its size and how urgently it needs to be disposed of.
Cutting into smaller pieces
Where small quantities of hedge trimmings or other slender growth are involved, woody materials can be snipped up and deposited back on borders and beneath hedges, or consigned to the home compost bin and mixed in.
If dealing with greater quantities it is best to use a shredder which will quickly reduce the volume of waste, turning it into a useful resource for the garden. Most domestic shredders will cope with woody stems less than 3-4cm (1¼-1½in) in diameter. Many shredders only mill timbers and may not produce fragments. However, milling will still speed up decomposition very effectively even though timber remains rather stringy. For thicker branches heavy duty shredders can be hired, or contractors with access to such machines can be engaged.
The resulting cut or shredded material can be:
Woody waste makes an excellent, long-lasting mulch for paths and borders and saves on costs from buying it in.
Being rich in carbon but low in nitrogen, shredded woody materials will need to be mixed with nitrogen-rich materials such as lawn mowings to increase their decomposition rate. It will take typically 3-4 years for woody chippings to break down into crumbly compost. Shreddings with a larger proportion of greener/younger wood may reduce the time required. Once well-rotted it can be dug into the soil to improve structure.
Used to build log piles and ‘dead hedges’
Unprocessed heavier timbers can be cut into lengths and stacked. When left to rot on their own, over long time periods, these log piles make excellent refuges for wildlife. This requires some space, but is very beneficial for biodiversity within a garden.
Again, where space allows, surplus woody brash that is too small to use in log piles can be arranged into a wildlife-friendly feature known as a ‘dead hedge’. Material is simply woven together into a line or used to infill between pairs of upright wooden stakes driven into the ground at intervals to form the basis of the hedge. As the brash collapses or rots down, more woody prunings are simply added to the top.
Alternative ways to deal with woody waste:
- Some timbers have potential, when sawn into logs or cut up as kindling, to become fuel for open fires and log-burning stoves (unless in a smoke control area)
- When dry, slender woody stems burn well in bonfires. However, bonfires create pollution and may also annoy neighbours. They should be conducted when wind and weather mean that smoke will not enter houses or inhibit others from enjoying their garden. Here are some government guidelines on bonfires in smoke control areas
- Garden contractors will remove and dispose of woody waste
- As a last resort light timbers can be bagged or bundled and taken to a green waste disposal site (seek guidance from your local authority)
Hiring or buying shredders
Whether to hire or buy a shredder really depends on how much use you anticipate making of it. For gardens with a lot of twiggy material from hedges, spent fruit canes and shrubs, it is probably worth buying an electric-powered shredder. These are relatively quiet to use and effective on smaller stems. It is more economical, however, for gardens with thicker or occasional prunings such as from fruit trees to hire a petrol-powered shredder once or twice a year.
Always ask the hire company for a demo or use the manufacturer’s instructions before operating garden shredders. Wear gloves and goggles to protect eyes from flying debris. Never try to force material through the shredder or unblock jams by putting your hand where there are moving parts. Many shredders can be unblocked by putting them into reverse.
As bark mulches rot down, it is not uncommon to find them colonised by white fungal growth or covered in a crop of toadstools. Thankfully these belong to saprohpytic fungi that are harmless to plants; they are simply breaking down the organic material. No action is required.
Studies indicate that wood and bark chip mulch made from diseased trees is unlikely to transmit pathogens to the roots of healthy trees, growing under good soil conditions. It is important that such mulches are not worked into the soil, as this will increase the risk. The RHS do, however, recommend that basal parts of trees infected with honey fungus, Phytophthora root rot, or parts of trees infected with stem diseases such as verticillium wilt or coral spot, are not used, to reduce the risk to plants.
Composting or burning wood from poisonous plants - there is no evidence that potentially harmful substances found in plants such as cherry laurel and yew are emitted when the wood is burnt, composted or used as a mulch. However, material from these plants can be stacked or ‘matured’ three to four months to ensure all harmful substances are broken down before use. For more on risks when shredding and using mulch from poisonous plants see our page on using woody waste as a mulch.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.