Mature Plants
If you are planning to try growing Disas, it is probably easiest to start with mature plants. The five main species (D. uniflora, D. racemosa, D. tripetaloides, D. aurata and D. cardinalis) and their hybrids can be grown under broadly similar conditions. D. racemosa might do best being kept drier in the summer (that is what happens to it in nature), and D. cardinalis isn't all that easy to grow. In nature, the evergreen Disas grow on stream banks, cliff faces or waterfalls where cool, aerated water is constantly moving through their root systems. The soil is derived from decomposing sandstone, with little or no clay particles; the water is very low in nutrients but contains humic substances that make it decidedly acidic. The habitats are open mountainsides, exposed to a bright sky but usually with some shading from too much direct sunlight. By bearing in mind the Disas' natural environment, one can better create the right conditions for them in cultivation. The "Disa culture" summary alongside should be helpful. For a more detailed description, click here. For even more detail, get hold of a copy of A Disa Companion, by Cywes, Harley and Linder (available on Amazon as a pdf) If you can't supply good quality water (low dissolved solids or TDS) don't even try Disas. Mike Gallagher, a good friend and Disa grower, would not sell a Disa to anyone who didn't have a TDS meter for measuring water quality. If your water measures over 100 ppm, try to find another supply. You will probably find it necessary to spray your plants with fungicide and insectide. Since Disas need to be constantly moist, frequent watering is essential. With just a few plants, you can stand the pots in a shallow saucer of water that gets changed at regular intervals. Or, you can water from above, just do it more often than for most other orchids. Large scale growers have been successful using "water tables". These are level tables, lined bottom and sides with waterproof material such as pond liner. Water is pumped in at one end of the table and flows to a drain at the other end, where it returns to a large reservoir that contains the pump. The pots simply stand in the water that is about 1-2 cm deep and get watered and fertilized by capillary action. The water flow can be continuous or be switched on and off with a timer. The plants should occasionally be watered from above to prevent a build up of salts in the medium. Since I only get to visit my plants once a week, I employ automated irrigation methods using a timer and some sort of pump. A complete, dilute, water soluble fertilizer is used in the irrigation water during growth periods. The plants can be watered in various ways. Regardless of what irrigation method is used, I try to change the water every two weeks. WINTER is the worst time for Disas in cultivation! Make sure they get the best light possible and plenty of air movement. If necessary cut back on watering, in order to avoid too wet a medium. Watch out for a stem rot that can overtake your plants if they don't like their living conditions. 1. Flood and drain (ebb and flow) Most of my plants currently grow on 6 ft x 4 ft water tables, lined with pond liner, that can accommodate twelve standard 10 x 20 inch flats, each containing 18 three-inch square pots, or more smaller pots. A timer controls a submersible pump that sends water onto the table, filling it to a maximum depth of about 1.5 cm. Once the timer switches off, the water drains from the table through a slow leak. A sketch of the water table system is shown on the right. The overflow water returns to a large reservoir (about 40 gallons) containing the pump. For many years my potting medium was Supersphag/Perlite, with a top dressing of crushed gravel that is intended to maintain a dry surface and limit the growth of algae and mosses. See sketch on the right. Recently I switched to coconut husk chunks and fiber, thoroughly leached to remove contaminating salts. This works well on its own or mixed with Perlite and/or peat. 2. Live sphagnum If you can grow sphagnum moss, you should try growing Disas in it. In nature, Disas are often found growing in association with sphagnum and other mosses. My Disas that are grown in live sphagnum do remarkably well, especially when they are in net pots. Here is a sketch showing how sphagnum can be grown. The main bulk of the moss is above the water level and gets fed and watered by capillary action. Water quality must be excellent and fertilizer levels need to be very low. Live sphagnum is also a wonderful "hospital" medium for ailing plants. If this doesn't cure them, nothing will! 3. Other options I have tried various other methods on my Disas, and have abandoned all of them. Here is a summary: Drip irrigation: Some plants did well, but the drip system was unreliable and some pots did not get evenly watered. Aeroponics: Initial response of the plants was great, but long term maintenance was a problem. Spray irrigation: Unless you take adequate precautions, this can encourage algae and unwanted mosses to grow on the surface of the potting media. Also, it is important that enough of the spray gets to all the pots. 4. Disa companions Another South African genus, Stenoglottis, seems to do well in broadly similar conditions to the Disas. Cultural details are a little different, since Stenoglottis have a short dormant period. While growing Disas in live sphagnum, I have also started growing Droseras (sundews) in the moss. These are very easy to grow (provided you don't use fertilizer on them!) and in my experience they are incredibly good at catching and devouring fungus gnats! That is a useful benefit, since fungus gnats seem to love being around Disas and the damp Disa media. For a more detailed, printable summary of Disa culture, click here. |
Disa culture
Water quality: critical; low TDS; no “hard water” Temperature: 0°C/32°F to 25°C/75°F Air: 50-75% humidity, good air movement Light: bright, use about 50% shading in summer Growing media: see below Fertilizer: complete, water soluble, very weak Watering: medium must never dry out! hydroculture Repotting: every year, usually in Fall Fungicides: may be necessary, unfortunately Insect pests: aphids, thrips, fungus gnats Media
General requirements: Constantly moist but never waterlogged Excellent drainage and aeration Mildly acidic Some specific solutions: Coarse quartz sand/grit (popular in South Africa) Supersphag:Perlite, 1:1 or 1:2 Sphagnum moss – alive or dead Peat:Perlite, 3:2 (Parkinson Orchids, UK) Composted pine bark, screened (fines) Coconut husk chips with peat and/or Perlite . |