The three factors to consider when deciding when to put an orchid outdoors are elevation, latitude and perhaps length of the dry season. The higher the elevation and/or latitude the earlier you can put it outdoors. For example, Dockrillia striolata grows all the way south to Tasmania which is at around 42S latitude. Dendrobium falcorostrum occurs at a lower latitude (around 30S) but higher elevation (around 1400m) where it occasionally snows.
Dendrobium bigibbum, however, occurs at around 12S latitude and at low elevations...where, to my knowledge, it does not experience any significant cold. But...some in the complex experience a fairly long dry season. For example, according to the book, "
Australian Tropical Orchids"... Dendrobium bigibbum var. bigibbum and var. superbum both experience a long dry season lasting around 7 to 8 months. Even though the book recommends that for successful culture they must be kept warm and dry during the winter and spring....so far I have not lost any of the half a dozen or so NOID Den bigibbum hybrids from the typical amount of cold and rain that we experience here in SoCal. They are all mounted so they dry off fast. My theory is that perhaps some of the same adaptations which allow an orchid to survive long dry periods also help enable it to endure periods of relative cold.
So if your Dendrobium bigibbum is one of the long dry season types...and it's not actively growing...you should be able to put it out fairly early in the year...especially if it has excellent drainage and receives bright light. Not sure how frequently it's raining over there but just to be on the safe side I'd recommend protecting it from the rain as well...at least until summer.
To help visualize the dry season here is a
climate diagram of
Normanton, Australia. Dendrobium bigibbum occurs further north but it's the closest location with climate data that most closely matched what was described in the book. The red line represents the average temperature (Celsius), the blue line represents rainfall (mm) and the brown area represents the period of drought...which appears to last around 6 months. The area above the red line and beneath the blue line represents the growing season and should ideally be shaded green but my Google Graph skills fell short.
Source: Weather Reports
Hybrid Mode
