uses for coffee grounds in your garden, coffee cups, coffee pots, poster

7 Uses for Old Coffee Grounds in the Garden

There are a few regular tea drinking readers who may be thinking “Uses for old coffee grounds in the garden are all well and good for you, Marie, you drink lots of coffee! But what about me?”

Would I forget you? No! You can be sure that –
1] there will be a blog on used tea leaves in the garden soon
2] you don’t have to be a coffee drinker in order to get hold of used coffee grounds

Explanation first:
Old or used, coffee grounds are those which have had hot water passed through them to make a cup of freshly brewed coffee.
The type of coffee – espresso, filter – is not important. Neither, for the most part, is the variety of coffee bean.

 

Where to get hold of free old coffee grounds:

  • Your own kitchen
  • Coffee drinking friends without gardens
  • Local independent coffee shop or café
  • National / international coffee shop chain

Important point
Like other organic and artificial materials you add to your garden, used coffee grounds do not suit all methods or all plants. So whilst you’ve read the ‘coffee grounds are magic’ you may also find ‘coffee grounds are rubbish’ in your internet searches. I have done my best to clarify why these conflicting claims have arisen and suggest useful uses for old coffee grounds in the garden!

 

Uses for Old Coffee Grounds in the Garden #1 Use as a Mulch

This use is where many people have issues. There are two main reasons why: –
1] caffeine is allelopathic. This means it may release chemicals which suppress the growth of plants nearby.
2] coffee grounds are, by their nature, fine particles. If you’ve tried to scoop out wet grounds from the bottom of a cafetière you’ll know how they stick together. On the surface of the soil as a mulch this may create a solid barrier which prevents moisture from reaching plant roots.

One of the solutions to #1 is to experiment. Not all plants will be affected and also caffeine levels vary, between beans and between processes. For example, I have found that tomatoes seem to be affected, whilst Hostas are not.

These solutions work for both problems:
Lightly rake the coffee grounds in to the soil so it isn’t lying directly on the surface. Mix the coffee grounds with another organic material. This is not necessarily by composting, but by chopping up leaves and using the two together as a mulch.

NB The caffeine in coffee is toxic to dogs. If your pooch eats everything it can, then this may not be a suitable use.

mulch, rhubarb, chives, kitchen garden, edible garden, compost, perennial fruit, perennial herbs

Uses for Old Coffee Grounds in the Garden #2 Add to your Compost Bin or Wormery

Despite its brown colour, coffee is a green element in the compost bin, having a higher level of nitrogen than carbon.

Compost Bin
You can throw in any remaining water in the coffee pot as well as the dried grounds to help keep your compost moist. As part of a mixed compost this is the easiest way to recycle coffee grounds. Some have declared the coffee acts as a compost activator, others have noticed no difference.

Wormery
Start slowly with adding coffee grounds. Worms seem to treat them like marmite! This is experiential evidence from my own wormery and those of clients. Due to the ‘caking’ effect, it is best to break up dried grounds and sprinkle them on.

pouring juice from wormery, liquid fertiliser, composting

Uses for Old Coffee Grounds in the Garden #3 Turn into a Liquid Fertiliser

Strictly speaking, a liquid fertiliser is made from fresh plant material so coffee grounds would be more like a cross between that and a compost tea. Be that as it may, the resulting liquid can be used to give your plants a nutrient drink.

However, choose your plants carefully, as some will just curl up and die. Others will lap it up. Yes, we’re back on topics such as caffeine poisoning and allelopathy!
For example, most Clematis hate it, Azalea are happy, Hostas don’t care.

If you’re experimenting, my advice is to keep the brew weak to begin with. Try 1 cupful of coffee grounds in a bucket of water. This is suitably vague as the coffee, and the water (tap, rain) are all variables.

 

Uses for Old Coffee Grounds in the Garden #4 Pest Repellent

Slugs and Snails
I’ve used this myself when the slugs and snails are heading towards my Hostas and its too cold for nematodes. Lightly raked into the soil to prevent a water proof cap, coffee grounds have worked as a deterrent. Improved by the addition of a few crushed eggshells sprinkled on the surface.
I’ve found coffee grounds less successful used as a pest repellent on the allotment. But that could be down to other factors such as playful foxes scraping soil and leaving gaps for molluscs to crawl through.

Cats, Foxes, Rabbits
Some people have found coffee grounds deter cats from using parts of their garden as a toilet.
Hasn’t worked for me; my cats like the smell of coffee (!) And it doesn’t seem to deter foxes either. Has put off a few pet rabbits of my acquaintance though.
Remember not to use coffee grounds too close to a seed bed or seedlings or germination and growth could be affected.

coffee grounds, coffee beans

Uses for Old Coffee Grounds in the Garden #5 Blooming Roses and Bananas

Brewing up a tea of old coffee grounds and banana skins and watering your roses with it does generally seem to result in a mass of blooms! And its not too smelly a liquid for humans. Make small quantities at a time and use promptly. A very rough ingredients ratio is 1 cup of grounds, 1 banana skin chopped small and a bucket of rain water.

A variation of this is to add the coffee grounds and chopped banana skin to the base of planting hole or trench when planting new rose bushes. Mix them with the compost / soil and they’ll work as a slow release fertiliser at root level.

Rosa bright ideas, bi-coloured flower, pink and white, repeat flowering rose, scented, deciduous shrub

Uses for Old Coffee Grounds in the Garden #6 Colour your Garden Furniture

Not necessarily a long-lasting fix, but a fun – and free – way to give your untreated wooden furniture a vintage look. There are various recipes and techniques out there, some involve vinegar, some use the grounds, some just the coffee water.

Try the colour out a couple on a spare bit of wood. Use the same wood as the garden bench you want to stain, as different woods have different absorbency rates. You’ll need to sand down the bench, table or chair first.

I have only tried this on a piece of wood, and it came out a pleasant sepia tone. I now have my eye on staining on a deckchair frame for next summer.

 

Uses for Old Coffee Grounds in the Garden #7 Use on your BBQ

Use on your BBQ or burn in your Chimenea. Not the loose grounds, but a ‘fire log’ made from compressed old coffee grounds. Now, before you start complaining about the amount of effort this might involve, may I just remind you that you can collect bucket loads of free coffee grounds from your local cafe. And it’s recycling a waste product rather than, for example burning charcoal.

Hands up, I haven’t actually made a log from coffee grounds (yet). Although I have burnt coffee logs. Because, if you don’t want the faff of making them you can buy them. I used those from a British, London based company, and I do know that there’s at least one American company as well.

Photo by Andrei Bocan on Unsplash, coffee, jug of coffee, record player

Uses for Old Coffee Grounds in the Garden – a few more tips

  • Coffee grounds generally have good levels of nutrients, including the three major plant nutrients of nitrogen, potassium and phosphorous.
  • They are also slightly acidic. However, coffee alone is not going to lower the pH of an alkaline soil, not even when you drink 10 espressos a day!
  • Slightly warm coffee grounds are okay to use. Temperature test: could you comfortably hold them in your hand?
  • Although you can store them for a couple of days, the grounds will start to go mouldy, this of course is fine in the compost bin, but not for all the uses.

 

Fresh coffee grounds also have their uses in the garden, and along with those used tea leaves, will be looked at in a later blog. What I wanted to focus on in this article was the re-use, re-cycle element benefits of old coffee grounds in the garden. Hopefully I’ve given you something to think about, a different way to look at that coffee you’ve been drinking whilst reading this!

Would you like to know how best to recycle, compost and generally have an efficient garden? Get yourself a copy of the monthly Plews eNewsletter and check out Plews Gardening Courses and Garden Consultancy services – they may be helpful to you.

 

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