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On 13/06/2023 at 05:33, Onoff said:

More coffee Sir? Ring fencing the plants with grounds, so far so good:

Maker

Why used coffee grounds may be doing your plants more harm than good

We are often told to add used coffee grounds to garden soil to perk up plants. But the science doesn’t support this, says James Wong

14 June 2023

By James Wong

R126CH Unrecognisable woman in casual clothing holding a box of used coffee ground to use as compost in her garden.

DGLimages/Alamy

WANDERING around an achingly cool San Francisco coffee shop a few years ago, I was fascinated to see huge, open-topped barrels filled with used coffee grounds and a sign saying they were free for customers to scoop into recycled bags and take home to perk up their plants. I realised that we had reached peak hipster.

Indeed, the claim that coffee waste dramatically boosts plant growth has been a staple of organic gardening books since at least the 1970s, and seems to be seeing a modern renaissance. Proponents everywhere wax lyrical about how the spent grounds are not only rich in nitrogen – a key plant nutrient – but can help lower the pH of garden soils for species whose roots require acidic conditions, like blueberries. It all sounds like such a brilliant idea: upcycling industrial waste into free, organic fertiliser. It is just a shame that in reality it is probably doing the exact opposite. Let me explain…

Coffee grounds, even after brewing, are still a rich source of caffeine. This compound seems to be produced by coffee bushes – at least in part – as a herbicide to suppress the growth of smaller competing plants. The phenomenon is called allelopathy and is a strategy loads of plants have evolved to help reduce the competition for light, space, water and nutrients around them.

Leaching out of the grounds, the highly soluble caffeine percolates through the soil and has been repeatedly shown to severely stunt the growth of small, neighbouring plants’ roots and slash the rate of seed germination, even at relatively tiny concentrations. Not exactly what the plantfluencers of social media promise.

The weirdest thing about how often this tip is recommended is that we have known about the allelopathic potential of caffeine in coffee plants for decades. The first paper I could find on this was from 1980, and its conclusions have been echoed by study after study. So effective is caffeine at suppressing plant growth, it has been investigated as a potential novel herbicide for agricultural use, both in the form of direct application of coffee grounds on farms in Brazil and even tea leaves (which also contain caffeine) on plantations in Vietnam.

This effect is so pronounced that over years of intensive cultivation, the accumulated caffeine in the soil of long-established coffee farms can reach levels where it doesn’t just hamper the growth of small weed seedlings, but even the mature coffee bushes. Studies have been conducted to see if underplanting coffee with more resistant herbs, like sage and oregano, could help reduce the caffeine contamination in the soil by drawing the compound up through their roots, while providing farmers with an extra crop to harvest. I wonder if the world is ready for caffeinated herbs. But that’s another matter.

James Wong is a botanist and science writer, with a particular interest in food crops, conservation and the environment. Trained at the Royal Botanic Gardens, Kew, he shares his tiny London flat with more than 500 houseplants. You can follow him on Twitter and Instagram @botanygeek

For other projects visit newscientist.com/maker.

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@SteamyTea the bloke who wrote that is wong...

 

Seriously though, point taken though a bit late now :( On the effectiveness as a slug/snail deterrent it's either that or the garlic water that's keeping them away it seems. Only two plants out of 50 have been nibbled and I found the culprit on one and dealt with it (small slug). I've also been putting human hair around the plants. 

 

If the caffeine is having a suppressing effect I wonder if it's worth giving each plant a liquid feed now?

Edited by Onoff
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53 minutes ago, SteamyTea said:

 

(expletive deleted)ing hippy.

 

Small weeds are still growing up around the beans so I'm not so sure the coffee is doing major harm? 

 

2023-06-17_11-49-11

 

Edited by Onoff
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Looks good to me.

Diy fertiliser has to be best. When it stinks so badly it must be effective.

 

For new readers.

Collect weeds especially the succulent green ones like dandelions and nettles.

Place in bucket and compress.

Fill with water and weight down with anything

2 weeks or so later it will be brown and stinky. Decant into a large plastic bottle, or lots of small ones.

Use slightly diluted.

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1 hour ago, saveasteading said:

Looks good to me.

Diy fertiliser has to be best. When it stinks so badly it must be effective.

 

For new readers.

Collect weeds especially the succulent green ones like dandelions and nettles.

Place in bucket and compress.

Fill with water and weight down with anything

2 weeks or so later it will be brown and stinky. Decant into a large plastic bottle, or lots of small ones.

Use slightly diluted.

 

Got as far as filling a bucket with nettles last year after a tip on here. Promptly forgot about it until it dawned what the smell was! Then the bucket dried out. Seem to recall you're supposed to dilute 10:1 as it's strong stuff.

 

Just given the soil around each plant about 100ml of this made up, organic fertiliser:

 

Screenshot2023-06-17140831.jpg.4e6948eaa0e291f413cf47713109ea77.jpg

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2 minutes ago, Onoff said:

Diy fertiliser has to be best. When it stinks so badly it must be effective.

Clearing the garden to my new cottage I came across a plastic bin full of this, when I took the lid off I nearly passed out, stank like a pig farm. 😵‍💫

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3 minutes ago, Onoff said:

supposed to dilute 10:1 as it's strong stuff.

I mix it at about that but I can't see it can do much harm, especially if from a good mix of plants.

It gives me some satisfaction to put nasty weeds through this useful end.

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Do they still use composted housse waste? Should be ok

 

I bought dobbies and westland but they seem identical certainly plants donplants don't like them: scrunched up trees I use it as a much because no weeds will grow.

 

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Now I'm scared! 😬

I thought I'd seen whatever it is the other evening but now there is no mistake.

I was just out slugging on the bean patch. There was "something" on the ground about 4" long. As the torchlight hit it disappeared underground but so fast I thought I was hallucinating. Where it went underground was a say 5mm dia hole. I gingerly probed it with the Leatherman blade but backed off as it's dark and I've seen Tremors!

Any ideas?

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A relative suggested they've had excellent first years growing veg then the second year seen the plants decimated by pests. Maybe "they" are then in the soil, multiplying ready for next year?

More hair applied to the nibbled beans tonight, purple dyed hair to be exact!

Dyed hair withstanding I'm trying not to use anything artificial. That extends to oil used on the gardening tools. Rather than 3 in 1, WD40 etc is vegetable oil an option? Was even thinking to spray inside my box section frames.

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I once tried to become a children's magic entertainer. Rather that make pigeons appear from a hat, or rabbits disappear, I put my hand down my trouser front, rummaged about a little, then produced two hairs.

Was not successful.

Should I have got my slug out?

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