Notes from a presentation by Brian Gerhard, owner of Down Under Native Orchids [DUNO]
Watering: Don’t water orchids. Especially during the winter, cut back on water. Be guided by the psuedobulbs: water only when they start to wrinkle. Watering should increase during spring and summer to every 2 to 3 days. [Watch a video clip of Gerhard talking about watering Dendrobiums.]
Fertilizing: Avoid high Nitrogen fertilizer. An overuse can lead to soft, fungi-prone growth and few flowers. Brian says this rule is true of all orchids. Also be aware of the percentage of urea in fertilizer. “To explain,” said Brian, “if you locate a fertilizer with an N (nitrogen rating of 15, & the percentage of urea was 8% in the overall mix of things, that would be OK, but if it was 15% Urea, NO, NO, look for another.” An 8-5-25 fertilizer is recommended. A 10-20-30 fertilizer in the U.S. translates to 10-9-25 in Austral.
Temperatures: Dendrobiums like a warm to hot environment. They can, however, withstand very cold temperatures for very brief times.
Pot selection: For rapid drainage, pots should have lots of holes in the bottom – more than most U.S. pots have. Plastic pots or clay glazed pots are good because they help retain moisture better than clay pots do during the summer. Elevate the pot so that air can circulate under its bottom.
Light: Bright light is good. Especially important is morning light.
Cool growing native Australian orchids, such as Den. bigibbum, have a drier dry season that other dendrobiums. Between late April and September avoid watering the plant unless the psuedobulbs become excessively wrinkled.