Flower Power

Is your garden in need of stimulation?

Mr. Kalsi, Chemistry Teacher

The idea of a Science newsletter came to mind when I looked at the large number of Science activities Bablake pupils are involved in. These don’t always manage to get a mention in existing publications.

I’m sure you are all aware of the need to recycle objects/materials to reduce waste. Whilst visiting the Morrisons’ store in Leamington Spa, I came across a sign saying ‘used coffee grounds work as a natural fertiliser if your garden is in need of stimulation’.

Many people choose to place used coffee grounds directly onto the soil, thinking that it will act as a fertiliser. However, this may not the case.

Coffee grounds need to be composted with other waste organic matter in order to provide nitrogen compounds that the plants may use. Others say that the benefit of using coffee grounds is as a soil conditioner, improving drainage, water retention and aeration in the soil.

Some think that coffee grounds lower the pH (raise the acidity) of the soil, which benefits certain plants. However, although fresh coffee grounds are acidic, used coffee grounds are almost neutral. If you rinse your used coffee grounds, they will have a pH of around 6.5 and the effect of this acid level(s) on the soil will be negligible.

Other gardeners suggest that using coffee grounds could be ineffective or, worse, harmful to plants. The reason for this could be that coffee beans contain caffeine, which is said to be produced by the coffee plant to suppress the growth of other plants in competition for space, nutrients, water and sunlight. How much caffeine actually remains in used coffee grounds is, however, debatable. In reality, it seems from the vast number of posts and stories on the Internet that many gardeners have indeed enjoyed success using used ground coffee as a natural fertiliser. They suggest that, to work best, the used coffee grounds should be mixed with the soil rather than placed on top.

All of this calls for a scientific investigation to find out if the coffee grounds do stimulate plant growth and how - is anyone up for the challenge?!