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Growing Aussie Dendrobiums
Australian Dendrobiums are becoming a popular plant for orchid hobbyists. Their tolerance to a wide range of temperatures makes them ideal for our weather conditions here in the USA. Aussie Dendrobium flowers are fragrant and come in many sizes and colors. In recent years the Australian breeders have made some significant improvements and their efforts have captured the eye of almost every orchid grower in Australia.
Watering and Fertilizing are related as water carries fertilizer into the root zone. Important for good Aussie Dendrobium growth is to have their roots dry down between watering. In the summer fertilize with every watering using a fertilizer solution of 100 PPM nitrogen; this equates to ½ tsp. in a gallon of water. In the summer when days are long and warm, the plants are in active growth and photosynthesis is at a high rate. As a result, you water and thus fertilize more, usually 2 times a week, however during the hottest period watering may be 3 times a week. During the cooler months, December-February, allow the plants to be totally dry before watering, generally every 10-12 days. In nature most Aussie Dens grow as lithophytes (on rocks) or epiphytes (in trees) which are well drained. The key to good Aussie Den culture is always check that the potting media has dried out sufficiently before watering.
Light levels, Temperature, and Air Movement. These are closely related, as light raises temperature and air movement cools it. Aussie Dendrobiums like light levels of about 2500-3500 foot candles (fc). For optimal growth I suggest growing under 55-65 % shade in winter and 65-75 % shade in summer. This is accomplished by adding a second layer of 30% shade cloth in late spring thru late summer. Also a Southern exposure or a location where the plants will receive plenty of bright, filtered light will work. The plants prefer summer day temperatures of 75-90 F and for winter nights of 45-55 F. Aussie Dens. are quite adaptable and short periods of higher or lower temperature usual don’t damage the plants. In nature Aussie Dens. receive abundant air movement. Your growing area needs to have good air movement for best culture.
Potting mix and Pots: I prefer the ‘Kiwi Orchid Bark’ brand of New Zealand Pine bark for growing Aussie Dendrobiums; it is hard and lasts 3-5 years. Douglas fir bark is also satisfactory. Use 3 parts bark with 1 part perlite. Strive for consistency in the potting media and adjust the particle size based on pot size. For 2-3” pots use fine grade bark and #2 perlite, for 4” pots medium bark and #3 perlite and for 5” plus pots large bark and #4 perlite. Plastic pots work well; they are inexpensive, light weight and readily available. However clay pots may work better in hot humid climates. Aussie Dens. don't like to be overpotted. Select a pot size that will allow for a maximum of 2 years of growth. Oversized pots take too long to dry out, causing root problems; remember, an important key to good Aussie Dendrobium culture is allowing the root zone to dry between watering.
Re-potting and Dividing: Aussie Dendrobiums start their growth cycle in the spring and new growths indicate new roots but always wait until you see new root tips before re-potting. Please don’t underestimate the importance of re-potting when new roots are starting to show, the stress on a newly potted plant is greatly reduced as the new roots will quickly reestablish it. Divisions should be made by cutting with a sterile tool or by pulling the bulbs apart. Try to keep the size of divisions between 3 and 4 bulbs. Remove ‘most' of the old media from the root system. Often the newest roots are so tightly intertwined with the old media and removing it is too damaging to them. As a result I may leave 5-10% of the old media in place in an effort to not damage these tightly intertwined newer roots. They are the most effective roots and minimizing damage will lead to a quicker re-establishment.
Australian Dendrobiums are new to the American orchid grower, the Aussies have been growing them for years, and they are one of the most rewarding orchid alliances. Their adaptability to a wide range of growing conditions, fragrance, and variety of flower color, shape and size makes these an excellent hobby plant. Everyone should have some in their collection. So why not grow and flower an Australian Dendrobium, or two or three, to perfection?
Fred Clarke, Sunset Valley Orchids
