Watering plants - what to look for in water?
How often you water a plant depends on the type of plant. There are plants that need quite little water. Other plants need very good and regular care and watering. Before water is used for watering, the water hardness, pH value, salt content and conductivity should be determined. The reason for this is that plants in the garden and potted plants have different requirements - not only for the soil, but also for the water with which they are watered in order to grow, thrive and blossom and bear "fruit".
The quality of the water used for watering plants depends on several factors. First and foremost, this includes the water hardness, whereby a distinction is made here between the total hardness and the carbonate hardness. The total hardness is the sum of all alkaline earths dissolved in the water. This is essentially calcium and magnesium. Carbonate hardness is also referred to as the so-called temporary hardness, which is ultimately decisive for the overall assessment of water quality. The reason for this is that the carbonate hardness has a decisive influence on the pH value of the water. As the term carbonate hardness already implies, this range of water hardness for pouring water refers to the amount of alkaline earths dissolved as hydrogen carbonate in the water, which leads to the notorious carbonate deposits when boiling or boiling down. Decisive for the quality of the water used for watering potted plants and garden plants is therefore the proportion of calcium and magnesium in the water used for watering plants. Too high a carbonate hardness value has a negative effect on the root zone, as the pH value of the soil or substrate increases. In addition, such a high value also leads to lime deposits in the irrigation system, i.e. the garden hose lines or any sprinkler lines.
Tap water vs. rainwater
If tap water is to be used as watering water for garden and potted plants, great caution must prevail. The reason for this is that tap water in some regions is very cold. This high lime content can be very harmful, especially for houseplants. For this reason, an appropriate filter must be used in this case. This filter reduces the lime content in the water. Some potted plants also tolerate mineral water - still water, mind you. The local authority will tell you whether tap water is suitable for watering. Of course, the garden and all its plants can also be watered with rainwater, which saves money and energy. Watering plants with rainwater should, however, only be carried out if it is ensured that the rainwater is obtained via non-polluted pipes and containers. In principle, the use of rainwater is considered to be hygienically safe for watering plants. Above all, watering garden plants with rainwater makes more sense than with tap water. This is because most garden plants tolerate rainwater better than tap water, which often contains lime. Rainwater, however, has no carbonate hardness and is therefore the ideal water for watering.
Rainwater is ideal for all plants
Indoor plants and thus potted plants - including orchids - can generally be watered with rainwater. However, the rainwater should be mixed with diluted condensation water in a ratio of 1:3. This water is then completely free of minerals and lime. However, the rainwater should be clean and fresh. Fungal spores, viruses and bacteria can thus not spread so easily. Rainwater that runs over roof surfaces made of zinc, bitumen and copper should not be used for watering the garden and potted plants, if possible. The collected precipitation should be collected in sealed containers. However, nutrients, i.e. calcium and magnesium, are missing when rainwater is used. This can be compensated for by substrates in the form of fertilisers added to the soil of the plants.
Rainwater is cleaner
Watering plants with rainwater has several environmental aspects. First of all, you save money. Rainwater is the oldest use for irrigation. Not only is rainwater clean - even though it lacks calcium and magnesium, it still has a high mineral content. It is important that the rainwater used for watering potted plants and for watering plants in the garden is in good order. While the plants cope well with algae and other things found in the rainwater, pumps and pipelines suffer greatly from contamination.