Upper North Shore Sydney Australia

Coffee and Firelight


A cup of fresh coffee in front of a fire might do more for your garden than you would have first thought.

Having recently moved to my new home in the leafy, bush suburb of Berowra, NSW I acquired a very efficient wood burning heater and purchased a new coffee machine both provide me with recycling waste. Apart from the sheer pleasure of enjoying the brew and the firelight what is left from this activity is grounds and ash. Both of these products can be used effectively into assisting you to build up the health of your garden soil.

Ash (from hardwood fires please) has many components that the soil requires. FireCalcium is the most abundant element in wood ash and gives the ash properties that are similar to agricultural lime. Ash is also a good source of common elements extracted from the soil and atmosphere during the tree’s growth cycle; potassium, phosphorus, magnesium, and aluminium. In terms of commercial fertilizer, average wood ash would probably be about 0-1-3 (N-P-K Nitrogen-Phosphorus-Potassium). In addition to these macronutrients, wood ash is also a good source of many micronutrients that are needed in trace amounts for adequate plant growth. Wood ash contains few elements that pose environmental problems. Heavy metal concentrations are typically low and not in a highly extractable or available form.

Field and greenhouse research have shown that wood ash has a comparative liming effect (lowering the PH value) of between 80 and 90% of the total neutralizing power of lime and can increase plant growth up to 45% over traditional limestone. Ash is best added to compost. If applied directly to soil do it in autumn or winter (how apt) well before planting or early growth emergence as you risk, short term, concentrated, alkaline conditions that could interfere with plant growth.

Coffee Grounds used directly on the garden should be laid out on a tray to dry in the sun then lightly raked into the topsoil. The easiest usage is simply add to your compost pile.  Research shows a varying in acidity depending on the age of the grounds;

from the fresh espresso puck (coffee grounds) – pH 5 to 5.5,

to grounds buried under soil layers (in a compost for example) for nine month – ph 6 to 6.5,

to vermicast from a worm farm fed a diet comprising 25% coffee grounds – ph 8.5 to 9.

So usage of these recyclables depends on what you want from them with regards to ph balancing.

If your soil needs a PH rebalance you can add ash to lower acidity or coffee to raise acidity. If you already have neutral soil then add the material to your compost and over time their PH will neutralise.

I particularly like the idea of feeding coffee grounds to my worm farms – there is  growing world-wide practice of collecting the grounds and also the husks off the coffee cherries to recycle as nutrient rich soil.