Depending on the type of gardener you are, you probably spend a lot of time investigating the type and quality of the water you use.  For normal recreational gardening and watering the lawn, tap water is just fine.  However, if you’re working with sensitive plants like orchids or young seedlings in a greenhouse distilled water is your best bet as all the harmful chemicals and impurities have been removed.

Below we take a look at how these two types of water affect different plants:

If your tap water comes from a well or municipal plant, it might be too hard for gardening and water softeners often contain ingredients like potassium and sodium which can be harmful to certain types of plants.

Greenhouse or indoor plants are especially vulnerable to contaminants in tap water as it causes chemical build-up around the roots. Unlike outdoor environments that are exposed to rainfall, impurities do not wash away in such a contained environment and remains trapped in the soil surrounding the roots.  This is why some people prefer to use rain or distilled water to irrigate their greenhouses and water their house plants.  Whichever type of water you use, always make sure it is room temperature, as ice cold or hot water can shock and even kill houseplants. If you have no other choice but to use tap water, leave it standing out overnight for the chlorine to evaporate.

The main reason distilled water is preferred for greenhouse gardening and hydroponics is because of its purity.  All unsavoury elements have been stripped and gardeners simply re-add the required nutrients in the form of liquid fertiliser or calcium and magnesium supplements to ensure their plants’ health.  Using distilled water allows you to adjust the mineral content to each plant’s unique requirements. Tap water is simply too hard and contains too much calcium and magnesium for these types of plants to flourish.