The hardness of the water is determined by the calcium and magnesium salts dissolved in it. It is influenced by the nature of the soil. In areas with a subsoil of water-impermeable or water-insoluble rocks – like quartz rock, Sandstone, crystalline shale and similar formations -will become the well- and spring water, similar to rainwater, be soft. The opposite can be found there, where water-soluble minerals occur in the soil; which influence ground and surface water to more or less great hardness. It is often very difficult to determine this; the waterworks will provide information in larger cities. It is usual, express the hardship in numbers; it is given in "German degrees of hardness" = ° dH. One should not use water for orchid care, whose value is above 4 ° dH. How to get suitable water, should therefore be quoted.
It is best to use rainwater, except in areas, where large industrial plants cause increased pollution of the air and the collecting areas. The washouts from the atmosphere, which contains the rainwater, make it possible for orchids to exist at home in the first place. Let’s bring ourselves to mind, what in the airspace, which the falling rain measures through, is included. The atmospheric dust contains mineral components of the soil, Rock- and wood particles, Pollen grains and other vegetable parts, Spaltpilze, Excrement u.a., what is thrown up by storms from the earth, Comes back to her through the rain. It is an enrichment of substances, which naturally correspond to the nutrition of the plants. However, they also change the pH value, which can be different for rainwater depending on the location and time of year. It should be measured occasionally. This is done through indicator paper, which one – immersed in the water and then compared with the supplied color scale – enables effortless reading of the displayed value. Small fluctuations are irrelevant, there is a margin of ph 5-7 in the area of portable stands. On the way to earth the rain becomes saturated with air. It contains about 78% nitrogen, 21% oxygen, 0,03% Carbon dioxide and traces of ammonia, Ozone, Iodine u. a. Fabrics. When storing rainwater for a longer period of time, there is no oxygen, which has recently been accorded great importance for the flourishing of plants. Oxygen has to be brought steadily to the plant substrate, both through adequate fresh air circulation and through oxygen-containing water. With this we promote the development of micro-organisms, which the disintegration of organic bodies into simpler ones, cause compounds that can be absorbed by plant roots. These aerobacteria need a lot of oxygen to exist. If the moisture in the plant matter is constantly too high and if there is a lack of oxygen, the plant matter will be decomposed by anaerobic bacteria, who live without oxygen, much faster. This leads to a compaction of the material, which is detrimental to the roots of the epiphytic orchids, which also need very much oxygen, and causes them to die off. It is of course impossible, constantly fresh – d.h. to have oxygen-containing rainwater available. However, you can re-oxygenate the stale with an aquarium ventilator; a possibility, which is recommended. Another method is that, Allow the plant material to dry out before watering it again and supply the necessary moisture to the plants under pressure atomization or misting in frequent repetitions.