Orchid Culture: Water

We have found watering orchids to be subjective. It depends on many different factors and because it is essential we thought that we would discuss this topic in detail.

Orchids have adapted to absorb water from all plant parts. Many have also developed water storage systems, somewhat like camels and cacti. By taking note of the physical structure, one can get a general idea of the water storing capabilities of each genera, species or variety. Also density of leaf and stem tissue and magnitude of the root system can give clues as to how long an orchid can survive between watering. It does not mean you are going to push the limits of drought tolerance, but rather use it as a gauge to determine the frequency and quantity of water that you are going to provide.

Orchids, when young, have a different and less developed water storage system than mature plants. So it is reasonable to assume that watering would be greatly divergent from their adult stage. As commercial growers we wish to optimize the growth and productivity of our orchid range. Watering plays a significant role in not only the quantity, but the quality of growth.

General cultural information about particular generas and even species are available through many published sources, as well as the web. So rather than trying to detail watering, I thought it would be helpful to convey some ideas that are the basis of our watering program.

Orchids not only need moisture at the root zone, but also oxygen. So media plays an important role in the schematics of watering. Some media, like bark, will retain less water than coconut and that may or may not be an advantage. Since we have two distinct operations in two varied microclimates, we have discovered the importance of tailoring the watering to the particulars. Our seedling operation located in Waimanalo tends to have a greater level of humidity, lower velocity of wind, direct sunlight cut short by the towering mountain range and greater collection of cloud cover than our blooming plant operation in Waianae.

Our Waimanalo facility is where most of the orchid seedlings are grown and is much like a rainforest.

Our Waianae facility rests in a parched valley where only Mesquite trees grow naturally.

An over generalization of watering for orchids is that we should water heavily when the media is barely moist. This is a good rule of thumb for most mature orchids with psuedobulbs, but for the commercial grower we may wish to alter this to some degree, to account for stage and season. During the growing season we provide more moisture and nutrients to take advantage of the extra solar radiation. Growing the plants slightly wetter makes sense if you desire rapid growth. Some growers feel you need to "play with your plants".

Remember about those water storage systems? Sometimes by bringing those systems into action we can stimulate the growth of those systems. So if you desire thicker psuedobulbs, it may be reasonable to assume that if you call them into action only occasionally then they will adapt and grow larger. If you overtax them then they will shrivel.

I'm not sure how many different orchids were studied, but an owner of an orchid nursery with stellar quality plants told me that orchids, unlike most plants, open their stomatas at night. What are stomatas? On the underside of the leaves of plants are respiratory openings that allow for gaseous interchange. When the stomatas are open, moisture escapes and thus provides the mechanism for water to move up from the roots. So basically he informed me that orchids like to go to bed with their roots wet but their foliage dry. This prevents the spread of fungus and bacteria that reproduce in wet conditions.

I have found that watering can be accomplished at any time of the day, or night. There seems to be advantages and disadvantages for both. In our Waianae facility we find that during the warmer seasons we can water at night, but during the cooler months fungus is more prevalent for spreading and makes watering at night prohibitive.

We like to keep a schedule in terms of the time of day we water, but we also like to keep the duration and frequency flexible depending on the prevailing conditions. When the plants are considered adults -- about two years from flask -- we water them thoroughly, and allow enough time for the media to dry to a barely moist level before watering again. Seedlings are generally kept moist to barely moist at all times.

Occasionally we may find it necessary to water more than once a day. But generally once a day or every other day is the norm. To encourage blooming some growers put their plants through a drought period. (Some dendrobiums actually require a dry period in order to initiate flowering.) Occasional dry periods seem to strengthen the canes of dendrobiums and encourage the development of more roots.

We don't think that trying to find a simple formula for watering is going to produce the highest quality plants. Adaptive watering, although inconvenient, seems to be one of the more important factors that leads to healthier orchids.