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So, I want to try recycling the water I use to rinse the coffee grounds out of my morning coffee.

The thought is, a plant of some description on the (north facing) windowsil of my kitchen. The question is - what sort of plant would a) survive that much coffee b) thrive on the reduced light level c) be edible/interesting in some fashion

Thanks :)

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  • What kind of quantity of water is involved, per day? – Highly Irregular Sep 18 '15 at 20:42
  • 120-200ml/day. While I often drink more coffee, the extra rinse water/coffee grounds will make it to the garden outside. But I dislike going into the garden on a cold, wet, rainy morning before having coffee. – user2702772 Sep 19 '15 at 8:30
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    Do you have a worm farm? You can give the worms the grounds and the water. Once the water filters through the farm you can put it on the garden/plants with the worm juice. Perfect! – Christian Sep 20 '15 at 4:59
  • I do not have a worm farm - more to the point, while I can slide a new (interesting/edible) houseplant round the wife, there's no chance I can get away with a worm farm. – user2702772 Sep 20 '15 at 7:14
  • You don’t have to go into the garden much if you save up the grounds (e.g. in a small plastic sieve) until the opportunity presents itself. – PJTraill Dec 8 '15 at 0:35
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I nearly killed a plant (grape vine) by discarding coffee grounds regularly into the pot, while working at a bar/café. I told the owner it was great for plants, but didn't realise they could actually get too much of it – that plant was getting a lot more than what you want to discard.

Coffee ground is great for composting, as it is rich in carbon, nitrogen (that needs to be degraded to become available to the plant), phosphorus, potassium, magnesium and copper. Worms also like it. But it can be acidic, which is a problem if used directly on the plant – although it might be neutralised quickly and other sources state they are not acidic enough to significantly alter the soil pH. Given that you might really pile it on, you might still want to choose more acidic substrate-loving plants: this page suggests "azaleas, rhododendrons, potatoes and blueberries". This page suggests "leafy vegetables such as spinach, tomatoes, corn, roses, camellias, rhododendrons and azaleas" because they like nitrogen-rich substrates.

My advice would be to go to a nursery and ask the staff for a plant that does not mind a tiny bit of acidity, a heap of organic matter, over-watering and low sun exposure. Also make sure the pot is big enough, and the substrate active enough (by using some healthy soil and compost) so the ground can be processed and the acidity buffered. Nutrient-rich organic material should remain a relatively small part of the whole substrate volume, and should probably be mixed in a bit to promote decomposition. Other (micro-)nutrients than the ones cited might need to be applied eventually, if the ground is the only fertiliser you apply.

side note: coffee grounds are great when added to soap for washing grease off your hands, so dry coffee ground pellets can be kept in a container until you need it after a dirty car or bike job.

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