Water – the source of life

Without water, there is no life. But water is not just water. Whether it is suitable for our orchids or not depends on how many and which foreign substances are in it.

The two most important values that help us to assess the quality of the water available to us with regard to our orchids are the conductivity and the pH value.

The conductivity of water indicates how well electricity is conducted in water. Pure (distilled) water conducts electricity very poorly. The more ions are dissolved in the water, the better the current is conducted. Conductivity (or EC value) is expressed in S/m (Siemens per meter). Since the units for our drinking water or our “orchid water” are significantly smaller than one siemens per meter – they are only in the micro range – the conductivity is usually given in µS/cm (microsiemens per cm).

A high conductivity of z. B. 800 µS/cm shows that there are a lot of dissolved salts (nutrients, trace elements and/or toxins) in the water. However, it says nothing about which substances are contained in it and in what ratio to one another.

In order to determine the conductivity, it is worth purchasing a conductivity meter (EC value meter). Simple entry-level models are already very inexpensive. If you want to deal with the matter more precisely and intensively, you can purchase a professional device that can be calibrated for several hundred euros. It is important that the device also measures the temperature and ideally converts it to a temperature of 25 °C – the conductivity is always specified at a water temperature of 25 °C.

Basically, orchids are so-called weak feeders, which usually do not need many nutrients to grow healthily. The smaller and finer the roots are, the less dissolved salts they tolerate. The following values can be used as a guide:

50 – 200 µS/cm for miniature orchids such as Pleurothallidinae,

200 – 400 µS/cm for small to medium-sized orchids such as Paphiopedilum, Cattleya or Phalaenopsis,

400 – 800 µS/cm for large orchid species such as Cymbidum and many medium-sized hybrids.

The pH value is of immense importance for all living things on earth. Enzymes, which are responsible for biological processes, can only fulfill their important tasks if the pH value is correct.

The pH value is the measure of the concentration of hydrogen ions or hydronium ions in a solution and lies between 0 and 14. The higher this value is, the more alkaline the water is. A pH value of 7 is referred to as a neutral value, which is neither acidic nor alkaline. Anything below this is acidic. Values above 7 are called basic (or alkaline). Only pure water has a neutral pH value at room temperature.

In orchid culture, the acidity indicated by the pH value has an enormous influence on the absorption (uptake) of nutrients by the roots. The best nutrients in the most balanced ratio are therefore useless if they cannot be absorbed by the plant due to an incorrect pH value. (See also: Boess, G. (2020): Heat damage to orchids – why is that? “Die Orchidee” 71(4): 270-271). (You can find the article here as PDF).

An ideal value for the absorption of nutrients is in the slightly acidic range, i.e. below 7. Values between 5.5 and 6.4 are generally the right pH values for a successful orchid culture.

It is always helpful to find out about the soil conditions and therefore also the pH value in the natural habitat of your orchids. Dr. Ernst Avenhaus has published an informative article on the influence of different substrates on the pH value in “Die Orchidee” ??(?), 2019? (You can find the article here as a PDF).

The pH value can be determined quite easily using litmus paper or digital pH meters. Some acids and bases suitable for plants are commercially available to adjust the desired pH value.

Water

Tap water

Although tap water in Germany is of drinking quality throughout the country, it varies greatly from region to region. In some regions it can certainly be used for the culture of hybrids and hardy species. But there are also regions where the conductance is much too high, which can lead to “burning” of the roots. This is reflected in brown areas that are really dry and begin to rot if there is too much moisture.

To assess whether the tap water is suitable for growing orchids, the conductivity and pH value should be measured or checked with the local water supplier.

Rainwater

If you have a garden or balcony, you can collect rainwater. This initially contains only a few dissolved salts, so it is basically well suited for orchid culture. However, there are local conditions that can cause the conductivity to rise too high and make the water unusable for orchid culture, e.g. air polluted by exhaust fumes, a roof contaminated by bird droppings, a corroded galvanized gutter, etc.

Aquarium water

As success in aquaristics also depends on good water quality, you can use the used water when changing the water, provided that the relevant values are maintained.

Distilled water

Distilled water is water that has been freed of all impurities by distillation. It can only be used for orchid culture if nutrients and trace elements are added to the water in the form of fertilizer. If used pure, the orchid would “starve” in the long run. On the other hand, it is well suited to prevent the substrate from becoming too salty, as it likes to combine with salts and flush them out of the plant matter.

By the way: Not every distilled water from the canister is really distilled. Very often it is actually demineralized water.

Demineralized water

This is water from which almost all foreign substances have been removed by a so-called ion exchanger. Therefore, nutrients must also be provided with fertilizer.

Simple water filters based on ion exchange for the kitchen usually remove too few of the substances, so that the water may not be suitable for sensitive orchids even after filtering. Professional aquaristic devices, for example, are much more effective and achieve almost as pure water as with distillation. However, the filter material of the ion exchanger must be chemically cleaned regularly. However, no excess waste water is produced, as is the case with osmosis.

Osmosis water

Similar to demineralized water, osmosis water is also filtered water that contains very few additives. Osmosis systems for private use are offered quite cheaply. Here, too, the orchid lover can set the right values after filtering with the right fertilizer and make the water usable for the culture.

A disadvantage of reverse osmosis is that it produces waste water whose conductance is then extremely high and is therefore no longer suitable for orchids. However, it can still be used in the garden and with insensitive indoor plants. Regular filter changes are also required for reverse osmosis.

Waters

Well water, spring water and water from rivers, streams and lakes vary so much from region to region that in some places it may be suitable and in other places it is definitely not. If you have access to such water, you can determine the important values and thus check whether it is high-quality “orchid water“ or not.

Water from the condensation dryer

This is where the experiences of orchid lovers differ. While some highly recommend it because it is essentially distilled water (through evaporation and condensation), others demonize it because the water may contain detergent and fabric softener residue, as well as residual fibers from the dried fabric. Again, the measuring devices help here, but also the human senses. If the water smells of detergent and perfumes or looks contaminated, it should not be used.

Water temperature

Last but not least, the temperature of the water also plays a role. It should be at room temperature and not deviate too much from the orchids’ normal ambient temperature. Plants that are very warm should also be watered with lukewarm water. On the other hand, orchids that are cultivated in the cold stairwell or in the cool area of a greenhouse in winter should not be given water that is too warm.

Even water in its coolest form – the ice cube – can be used in orchid culture. As Thomas Jacob explains in his article on Disa uniflora, he places ice cubes on the substrate on hot summer days to keep the roots cool. Disa uniflora grows in Africa right next to mountain streams and rivers, whose cold water regularly washes around the roots.

Dipping – watering – spraying – semi-hydro

Now that we have thought about the water quality, let’s look at the watering itself. For this we have to look at the climate in the natural range of the species to be cultivated. What are the temperatures? How much precipitation is there? How is it distributed over the year? Is there a dry season? How long does it last?

Some orchid species go through a distinct dormant period with little or no rainfall. If you water too much during this time, there is a high risk that the plant will rot and die. If in doubt, you should water a little less and watch the plant, because orchids rot rather than dry up.

In general, one can say that at higher temperatures in the culture room, more water is required, especially in summer during the growth phase.

Depending on the requirements of the plants, the time of year and the temperature, the following methods of watering orchids have proven effective:

Dipping

When dipping, the entire pot or, in the case of tied or bare-rooted plants, the entire root area is immersed in water and allowed to soak for a few minutes.

Too dense or old, decomposed substrate dries very slowly after diving. Therefore, potted plants should be carefully watered rather than submerged, especially during the cooler winter months.

One disadvantage of dipping is that you have to pick up every pot.

Watering

The famous “shot glass a week”, which is supposed to be enough for orchids, is usually not enough. Nevertheless, the normal watering, as we practice it with many other potted plants, can also be used for orchid culture. The substrate does not soak up so much water and dries off more quickly, which reduces the risk of rotting roots.

Especially in the cool winter months, watering is a good choice for many species and hybrids that do not want to be too moist and are going through a more or less pronounced rest period. Depending on the plant’s individual moisture requirements, watering can be either thorough or sparing.

Spraying

Spraying is generally a very natural way of watering. Finally, it simulates the rain in nature. However, there are some difficulties here, especially when it comes to culture in the living space. With insufficient air movement, water on the leaves or in the heart can cause rot if it doesn’t dry off quickly enough. This is especially true at lower temperatures. Fans can help.

Spraying to increase the humidity in the room is mostly useless. Although the humidity rises sharply for a short time, it falls to a similarly low level as before after just a few minutes. Humidity lasts much longer in a greenhouse or orchid display case. For this reason, special attention must be paid to factors such as temperature, air movement and air exchange when spraying.

Semi-hydroponics

In contrast to hydroponics, with semi-hydroponics the roots of the plant to be cultivated do not grow in water, but in the planting material, which either stands in a little water or is kept permanently moist using the wicking method and a water reservoir. Such systems can be bought ready-made or built yourself.

In another method of semi-hydroponics, the plants are planted in a closed container in which some water always remains at the bottom. When it’s used up, it’s poured again. Transparent vessels help control the moisture in the plant matter. The method is also known as SGK (substrate glass culture).

If the right plant material is used, semi-hydroponics is suitable for those orchid species and hybrids that like to be constantly moist.

Some species of orchids also like wet foot culture. Here the pot is in a bowl, in which there is always some water. This method is particularly recommended for mineral substrates and is very successful even in normal bark substrates, for example with Phragmipedium . The big advantage of semi-hydroponics is that you only have to spend a very short time supplying the orchids with water.

Conclusion

Taking a quick drink of water from the tap is usually not enough for orchids. If you are serious about your culture and want to achieve success, you should also deal with your water and watering behavior. A large part of the cultural mistakes can be found in the subject area around water.