''I read somewhere that coffee grounds are a great natural deterrent to snails & slugs. My grandad and nanna used to empty the tea leaves in their garden at the back door and, after many years, it grew into a thick carpet. Anne won't allow that, but she did start piling coffee grounds around her veggie patch. Then disaster. The pea plants seem to have objected to the coffee grounds. The stems turned a sickly grey before they died. Failed experiment, no peas this year.''

Coincidentally I'd just come in from throwing out yesterday's coffee grounds to make a new pot. We do tend to produce a lot of coffee grounds. So I sent back this:

"Slugs and snails are not very bright and so are reputed not to like caffeine, and so avoid coffee grounds. I've tried using strong coffee as a snail and slug repellent on lettuces, but it didn't work, so suspect the slugs and snails avoid the rough coffee grounds rather than any caffeine content, as the grounds irritate sensitive under regions. Use a barrier of coffee grounds around the lettuce, and slugs will mostly avoid it, though the odd slug of great machismo may see it as a challenge to be conquered.''

I use coffee grounds a lot in the garden, mostly because I have a fresh batch of grounds to throw out at least once each day. Coffee grounds are excellent fertiliser, especially for coffee bushes, but I also pour mine on the pelargoniums and thyme bushes - the grounds also act as mulch covering the old thyme stems, so they put out new healthy shots. Coffee grounds added to the dry dust under the leaves can help turn it into fertile, moisture-retaining soil.

But a thick layer of coffee grounds can also become cloggy, and breed extremely interesting moulds and mildew, as anyone who doesn't clean their coffee pot often will discover. Peas will sigh and fall victim to any mould or mildew within a 5-kilometre radius (this is a metaphor, not peer-reviewed science) so don't mulch pea stems with anything that might be mouldy or mildewy. This sometimes includes lucerne and other hays. Peas also need a loose mulch for the same reason, and coffee grounds are most definitely not.

Keep the coffee grounds for the plants that love them, and you'll have the most magnificent pelargonium display in the neighbourhood.

So what else can happily land on your garden beds? Tea leaves, with the same proviso as coffee grounds, but not tea bags, as they have nasty threads that might wrap around the legs of lizards et al. Tea bags must be composted (which needs a whole other article to explain). Never buy tea bags that have those tiny bits of metal stapling them together. Invest in a metal tea bag if you don't want to go the tea pot route, and fill it afresh each time you want to make a cuppa.

Just about anything else that has once lived, from bristle doormats to cotton night dresses, can be composted, though it speeds up the process by a few years if you shred them all first. Odds and ends of wool I threw away decades ago soon vanished, but after 20 years I finally emptied a compost bin to find a natural wool beanie I had knitted and accidentally thrown away still entirely intact.

It may be tempting to think of cabbage leaves or limp silver beet as mulch, but they will smell a bit as they do so - elderly cabbage is not the perfume you want to waft through your back door - and they will also stop small rain showers penetrating the soil.

I'm not sure how long it takes for a geriatric cabbage to turn back into soil, as I've had chooks most of my life. A happily guzzling mob of chooks gets rid of a surprising amount of what other households might think of as waste. Paper also tends to create an impermeable barrier on top of the soil for a pressingly long time, as in months or sometimes years, unless you shred it up with lots of coarser material like wood chips, or have an extremely large garden with lots of larger mulch loving trees, where you can scatter scrunched up pages and let the lyrebirds shred them and return them to the soil. One lyrebird can turn over 150 tonnes of soil a year, though it seems like a lot more when they get into the strawberry bed.

Lacking lyrebirds, you will need to shred and compost. Meanwhile, don't waste the coffee grounds.