Growing Angraecum Orchids using Semi-Hydroponic Techniques. By Chris Johnson After I found Tom’s great Angraecum orchid blog and the related Facebook page, I sent Tom a few questions regarding Angraecum culture and made a few posts to his blog. One day I was repotting some Angraecum magdalenae seedlings to larger pots and I sent Tom a photo (Figure 1) of one of the seedling’s roots growing in semi-hydroponic media before repotting. After seeing the photo, Tom thought that other folks growing Angraecums might be interested in learning more about growing them (and other orchids) in semi-hydroponics.

Figure 1. Angraecum magdalenae seedling growing in semi-hydroponic media, ready for repotting to a larger pot.

I started growing orchids the way I suspect most people do. I’d purchased a wonderful orchid at the grocery store, but I was unable to get it to bloom again. I started reading about orchid culture on websites and in books and figured out that our very dry weather in Salt Lake City was not optimal for most orchids. I decided to purchase an Orchidarium, which is basically a Wardian case in which one can control temperature, humidity, and air flow. You can purchase (or build)

one to suit your orchid needs and budget. My first orchidiarium is shown in Figure 2. As you can see, at this point, all of the orchids are potted in traditional media.

Figure 2. Orchidiarium (Grand Cayman option). After having significant success in growing orchids in my orchidarium, I purchased a second and then a third orchidarium and I eventually built a greenhouse to hold my expanding collection of mostly fragrant orchids, including Angraecums, Cattleyas, Dendrobiums, Lycastes, and Zygopetalums, among others. As my collection grew, however, I realized that the various orchid types had different culture needs and, in particular, different watering schedules. For my job as a Professor of Computer Science and director of a large research institute, I have to travel both nationally and internationally multiple times a year. There was no practical way I could keep up with so many orchids with so many different watering needs given my travel schedule. Fortunately, I happened upon an article in the November 2006 American Orchid Society’s Orchids magazine called “No Longer a Killer” by Charles Rhodes (http://firstrays.com/semihydroponic-culture/no-longer-a-killer-aos-article-by-charles-rhodes/). In the article Charles describes using a technique called semi-hydroponics, created by Ray Barkalow, that can be used to grow most kinds of orchids. Barkalow developed the technique in part because he had a busy travel schedule and

needed an easy way to water all of his orchids at the same time. Fortunately, Ray keeps a wonderful website dedicated to using semi hydroponics to grow orchids (http://firstrays.com/semi-hydroponic-culture/general-semi-hydroponicsinformation/), which I devoured. I then started experimenting with semihydroponics myself. One main feature of semi-hydroponics is that instead of using an organic potting medium such as bark or sphagnum moss it relies on an inert clay aggregate media called LECA (Lightweight Expanded Clay Aggregate). There are many brands of LECA, including Hydroton and PrimeAgra. The LECA won’t decay over time like bark and sphagnum moss and so provides a stable medium, maintaining a constant supply of moisture with good wicking capability and providing good air flow to the roots. According to the technique, I plant my orchids in plastic pots with one or two ¼” holes drilled about one inch from the bottom of the pot to provide a water reservoir. I water them by filling up the pot to the top with water and allowing the pots to drain. The frequency of watering is determined by the season, temperature, and specific orchid (as with all orchid potting materials).

Figure 3. Angraecum magdalenae potted in a plastic pot with PrimeAgra LECA media. A ¼” hole has been drilled one inch above the bottom of the pot. You will notice the ¼” black tubing with a flow rate valve. All of my orchids are watered (pots filled to the top and allowed to drain) using an automatic watering system shown in Figure 4.

Figure 4. Automatic watering system. More details of the watering system can be found here: http://www.firstrays.com/forum/viewtopic.php?f=5&t=294

One of the most important considerations when moving orchids that have been growing in traditional organic media to semi-hydroponic LECA media is timing. You want to make sure there is new root growth on the orchid before transferring it to LECA, as when transitioning an orchid from any type of growing medium to a considerably different type (or even from the same medium if the old medium is quite decayed, as the medium properties will be significantly different between old and new media). It takes a while for the orchid roots to adapt to the new medium. Here are two good links that describe the process of moving orchids from traditional media to LECA: http://www.interiorwatergardens.com/cultural_files/hydroponics/a%20simplified% 20method.html and http://firstrays.com/semi-hydroponic-culture/general-semihydroponics-information/repotting-into-sh-from-traditional-media/

Once the orchids are well established, they grow very well. Repotting is very easy because you can just lift out the orchid from the old pot and then put it in a larger plastic pot and fill it up with more LECA. I have orchids growing in small 3” pots all the way up to large orchids growing in 18” pots using semi-hydroponics.

I’ve had a lot of success growing a number of Angraecums in semi-hydroponics, as you can see in the photos below. If you are looking for an easier way to grow Angraecums and other orchids, you might give semi-hydroponics a try.

Angcm. Memoria ‘George Kennedy’

Angcm. Crewtwood ‘Tomorrow Star’

Angcm. Longiscott

Angrcm. Magdalenae

Angrcm. Lemforde White Beauty

Angrcm. Sesquipedale

Angrcm. Sesquipedale ‘Phantom Flourish’ x ‘Flambouyant’