The branches and leaves are very acidic so can upset the balance of your compost heap and later, your soil. The resin can also be toxic, so be careful of that.

Even shredded into small pieces or run over by a lawnmower, conifers take ages and ages to rot down (three to five years isn’t uncommon). (Their acidity and their rubbery leaves make it difficult for composting bacteria to do their magic.)

If you’ve got a lot to get rid of (and if you’ve got leylandii trees, that’s very possible), consider starting a special slow compost heap to avoid interfering with the speed of your normal one. Or find another use for them: some people take advantage of their slow-rotting nature and sprinkle them on muddy garden paths.

Alternatively, you can use your council’s local green waste recycling service to get rid of them: they might be unsuitable for a basic compost heap but industrial composting processes can deal with them much more successfully.

Also see: How can I reuse or recycle leylandii/conifer trees and branches?

The smell of rotting meat or other meat products is likely to attract rats and other animals to your compost heap so best to avoid adding it if possible.

(Some people with completely sealed bins or very active wormeries are happy to add meat, particularly just little scraps.)

You should also avoid adding things that have come into contact with meat (eg, during cooking), even if you could normally compost them. For example, onions are fine to compost but onions cooked underneath a pork or beef roast will have soaked up meat fat and juices so shouldn’t be composted.

Similarly, bones including chicken carcasses should not be composted – not only might they attract rats and the like, they will take years and years to break down.

Most condoms are made from latex (rubber), a natural biodegradable substance, so they will break down in time – but that will take far too long for basic garden compost heap. The latex is often usually adulterated with synthetic materials too – either in the material or due to added lubricants etc – which might slow or impact its decomposition.

Non-latex condoms are typically made from polyurethane – a synthetic non-biodegradable plastic – so they won’t break down at all. Neither will the plastic & foil wrappers that condoms are sealed in prior to use – definitely leave those out of your compost heap too.

(As much as we hate sending things to landfill, the best way to dispose of condoms is simply wrap them in a little tissue paper/toilet roll and throw them in your regular rubbish bin. Flushing them is even worse than trying to compost them. It causes lots of problems in the sewerage process and can, in some circumstances, end up in the sea or rivers with other waste water. They also won’t break down as easily in water – there aren’t enough decomposition microbes around – so they’ll end up bobbing around for years.)

Though wet wipes are usually made from paper (“air-laid” to make it soft, fluffy and absorbent), they sometimes include synthetic fibres to increase softness or durability. Synthetic fibres will not decompose on a compost heap – they will break up rather than break down, leaving lots of tiny synthetic fibres throughout your lovely soil.

The “wet” bit of the wipe is also problematic – depending on the type of wipe, they’re impregnated with various chemicals such as moisturising lotions, detergents or perfumes. Most people do not want unknown chemicals introduced into their compost, especially if they will be using it on veg beds or the like. Anti-bacterial wipes or those containing isopropyl alcohol can also have disrupt the delicate microbes in your compost heap – the ones that are essential for speedy and efficient decomposition.

Finally, items cleaned up using wet wipes can cause composting problems too: oils/greases or dairy products might attract rats or other unwanted visitors to the heap; human fecal matter may introduce nasty pathogens to your compost; cleaning products, especially those containing bleach or other antibacterial properties, can kill off friendly composting bacteria; and finally, things like paint or engine oil can have a serious environmental impact.

As well as not being added to a compost heap, wet wipes should never be flushed down a toilet – they can cause problems for sewerage works as they do not break down like regular toilet paper. If you are worried about the amount of wet wipes you are sending to landfill, consider moving onto washable cloths instead of wipes. Reusable cotton wipes can be composted at the end of their lifespan – which will be a whole lot longer than a single use wipe.

Two reasons:

1) Use of plastic and chemicals in the absorbent layer – they won’t break down but it might break up and contaminating the rest of the compost.

2) The human faeces issue

Disposable nappies, unfortunately, have to be sent to landfill.

Bindweed, whether an undesired weed or a desired pretty flower, shouldn’t be composted because it’s so dang determined to regrow.

The tough, creeping roots can regrow from a small fragment just an couple of inches long and it is aggressively self-seeding, with each plant producing up to 500 seeds which can remain viable for 20-30 years!

Even if your compost heap is hot/efficient enough to break down the roots, the seeds can hang around in the compost once you’ve spread it back on the garden and voilà, bindweed a go go.

It’s just not worth the risk.

Glossy paper, such as that used in catalogues or take-away menus, is often coated in plastic or otherwise uses synthetic materials to achieve shinyness.

The inks used on brightly coloured brochures can sometimes be toxic too.

(Newspaper-like catalogues – black and white print on low quality paper – can be composted as if they are newspapers though.)

If you’d prefer to reuse them or can’t recycle them in your area, they can be used as the raw material in various crafts.

Also don’t forget to reduce if you can – unsubscribe from mailing lists and only pick them up in store if you really need them.

Glossy paper, such as that used in magazines or take-away menus, is often coated in plastic or otherwise uses synthetic materials to achieve shinyness.

The inks used on brightly coloured magazines can sometimes be toxic too.

(Newspaper-like magazines or zines – black and white print on low quality paper – can be composted as if they are newspapers though.)

If you’d prefer to reuse them or can’t recycle them in your area, they can be used as the raw material in various crafts.

Also don’t forget to reduce if you can – some magazines let you switch to the greener (and often cheaper) option of reading them online or through phones/e-readers. Or if they’re popular, your local library might hold them. Finally, if you must buy them, pass them on to others before recycling them.

It doesn’t matter whether it is sponge, pastry or fruit/mousse-based like in the picture – it won’t add a lot of nutrients or bulk to your compost heap and while it will rot down quite quickly, they might attract rats or other vermin to your compost heap in the meantime. The reward isn’t worth the risk.

Instead, use it up – even dry or going stale sponge cake can be turned into treats. Use in a trifle, as part of a pie biscuit crust or bake them into biscotti or sweet croutons. For more ideas, see our Recycle This page about things to do with old cake.

The benefit of adding waste cooking oil to a compost heap are vastly outweighed by the potential problems. Not only can they attract rodents and other undesirable creatures to your compost heap, they can cause problems for the composting process: the oils can form water-resistant barriers around other material, displace water and reduce air flow in a heap, thus slowing down the composting process.

However, vegetable oils such as rapeseed oil, sunflower oil, corn oil or olive oil can be composted in very small quantities as long as they haven’t come into contact with any forbidden food stuffs (like meat, cheese or fish). If you’ve soaked up a bit of oil with some kitchen roll, that’ll be ok to add but don’t pour the contents of a deep fat fryer into your compost bin.

Large quantities of used vegetable oil can be recycled – your local council should be able to advise if it is possible in your area.

Some people use leftover cooking oils that are solid at room temperature to make bird feeders (fat balls) for the garden.

Waste cooking oil should NOT be poured down the sink – it can clog pipes and sewers.