Most gardeners have at least some understanding of the term Hydroponics. Hydroculture is a form of hydroponics that has distinct advantages for growing and enjoying orchids. Hydroculture is also referred to as passive hydroponics or semi-hydroponics, a term popularized by Ray Barkalow.
Hydroponics is generally considered to be a high tech (and perhaps expensive) form of gardening without soil. Alternatively, hydroculture is a low cost, low tech, alternative that does not use the pumps and recirculation systems generally associated with ebb and flow, and most other forms of hydroponics systems. There are three important factors which together form the hydroculture system. These components consist of special planters which facilitate water storage and distribution, use of an innate media with specific qualities instead of soil and nutrient solution.
The most common form of orchids grown in the home or greenhouse are epiphytic orchids. They grow in trees in the wild. If an orchid comes potted in a course, quick-draining medium, generally some form of bark, it is likely a type of epiphytic orchid. The quick-draining material is designed to help replicate short but heavy rains that occur in the plants natural environment. Epiphytic orchids and others can thrive in a proper hydroculture environment, and the following popular varieties have been proven to do exceptionally well: Paphiopedilums, Phragmipediums, Masdevallias, Phalaenopsis, Cattleyas, Cymbidiums, Oncidiums, Dendrobiums, Epidendrums, Miltoniopsis, Pleurothallids and Zygopetalums.
Before looking at each component that makes this system successful, let’s take a look at the advantages of growing orchids with hydroculture.
Cleaner than soil or bark – The media used for orchid hydroculture is generally a pellet form of expanded clay similar to a small pebble making it easier to clean up spills and less likely to stain furniture or flooring.
Non-allergic – By growing in an innate composite rather than soil many of the allergies caused by fungi, mildew etc. are avoided.
Grow medium never needs to be replaced – Orchids are generally purchased growing in some form of bark or
other organic media. This organic media is continually broken down by micro organisms and eventually loses its necessary water and air holding capabilities if it has not lost them already. If the right forms of innate media are used, they will not break down and can even be reused if reconditioned properly.
Odor free – Odor problems associated with orchids and other potted plants are generally the result of decomposing organic matter. By growing in an innate medium this problem is eliminated.
Good root aeration – The various hydroponic media available contain more air space than traditional potting mixes, delivering increased oxygen to the roots. This is particularly important in preventing root rot in epiphytic plants such as orchids, whose roots are exposed to the air in nature. When using the proper growing medium, superior and consistent root aeration is obtained because pebbles do not compact.
Reduced Pest Problems – Because many of the pests that cause problems for orchids depend on organic soil, or growing media for food and procreation, pest problems can be greatly reduced or eliminated by using innate growing media.
Greatly Reduced Watering – Depending on the particular planter used, and the reservoir size, orchids grown in hydroculture may only need to be watered every 1 – 3 weeks. This can be a distinct advantage for frequent travelers.
Take the Guess Work Out of Watering – Hydroculture planters make visual inspection of water levels easy. When water reservoirs become dry, they are simply refilled with nutrient solution.
Healthier, Faster Growing Plants – Because hydroculture provides more consistent air, water and nutrient supply, plants are healthier and grow faster.
Less Chance of Over Potting and Need for Repotting – Hydroculture provides a much healthier environment for roots causing plants to have more healthy root systems that require less frequent transplanting.
Less Work – Since routine maintenance is much simplified, passive hydroponics can reduce the labor required for maintaining a large collection of plants.
The goal of a hydroculture planter is to provide a reservoir in which one inch of nutrient solution can remain at the bottom of the planter in contact with the growing medium. The simplest setup is a container with sufficient drainage slots or holes on the sides, from the bottom to one inch up the side, paired with a deep saucer, to allow the bottom inch of growing media to remain submerged by adding one inch of water to the saucer. By using a saucer with a circumference substantially larger than the container, plants can go longer between watering. There is also the benefit of creating a more humid micro climate around the plant through evaporation with this method.
A variation of the above method uses a planting container with a few small holes one inch up the side from the bottom. In this case a saucer is used only for overflow when watering, as there are not holes lower than one inch to allow the saucer to “feed” the container. Because the saucer is not being used as the reservoir, it is necessary to use clear or semi-clear containers for this method so that the water level can be monitored and replenished when empty.
There are also containers available which are specifically designed for hydroculture. These generally consist of an inner pot to hold the growing medium, an outer decorative pot, which serves as the reservoir, and a water level indicator. These are often called “culture” pots, or “self watering” pots. The term “self watering” often refers to a similar system for soil based plants, so care should be taken, when buying these pots, to insure that they are intended for use with soil less medium.
Proper growing medium is at the heart of the hydroculture method. Above all, the medium must have excellent wicking characteristics so that moisture is continually transported from the reservoir in the bottom of the planter upward through the medium to keep it uniformly moist. In addition to retaining water, the medium must be fairly uniform in particle size so it provides ample free air spaces to deliver oxygen to the roots.
The most common media for growing orchids with the hydroculture method is LECA (Lightweight Expanded Clay Aggregate) – This product is manufactured under several different trade names and is sometimes referred to as fired clay pebbles, grow rocks, expanded clay (pellets) or hydrocorns.
It is a good practice to repot epiphytic orchids after purchasing so this is a great time to make the switch to hydroculture. Often these plants have been growing in the same pot for some time and the growing medium may have begun to decompose. By repotting in innate media, one can insure that the orchid is in fresh medium with quick-draining characteristics and that the roots are well conditioned.
Clay aggregate should be rinsed and soaked overnight in water adjusted to a pH of 5.5-6.8. Remove the orchid from the old planter and thoroughly remove the old medium from the roots. Cut away any rotten roots and trim any overlong roots. Next, thoroughly wash all the roots in lukewarm water. Arrange some of the new expanded clay medium at the bottom of the new planter. Place the orchid on top and place more new medium is around, the roots. This can be accomplished by gently shaking the planter as more media is put in, more shaking and so on.
One of the neatest things about the hydroculture method for growing orchids it that is takes the guess work out of knowing when to water. The reservoir is simply filled to allow one inch of water to remain in the bottom and then allowed to dry completely before refilling.
Because hydroculture uses an inert growing medium without organic components, all nutrients needed by the plants must be provided in the nutrient solution that is used for watering. The best option is to use products that are 100% water soluble and designed for hydroponics. Nutrients necessary for plant growth are optimally available to most plants, including orchids, in a general pH range of 5.5 to 6.8. Many commercial water-soluble fertilizers are made to ensure that the resulting dilute solution falls in this optimal pH range, but depending on the water source you are using it is a good idea to check the pH after mixing nutrient solution to make sure it falls within the proper range and adjust accordingly if necessary. Products for adjusting and testing pH are available from some of the sources listed at the end of this article or wherever hydroponics supplies are sold.
Most of the time orchids do well with a balanced fertilizer. It is possible to use a high nitrogen fertilizer to increase lush foliage, but if this is continued for too long, or into the blooming season, the high nitrogen will cause the plants not to bloom. A nitrogen dosage of about 100-150 ppm is sufficient. A high phosphorous fertilizer is needed to give orchids the energy needed to grow new blooms and flowers; so many growers even switch from a balanced to a “bloom” formulation when orchids begin budding.
In order for nutrients to be continually available to orchids grown in hydroculture a nutrient solution is used at every watering, however it is important to avoid over feeding. This is best done by using 1/2 or 1/4 of the recommended strength of balanced 100% water soluble fertilizer with every watering. The exception would be if using a formulation specifically designed for hydroponic orchids, in which case, follow the instructions for mixing the product. Additionally, it is important to thoroughly flush the planter with plain water every month to prevent harmful salt build up.
Dr. Christopher J. Kline is a master gardener and writer living in Paradise Valley Arizona.