Dendrobium hasseltii is a variable species both in plant size and flower color. My plant is very small, only 8 cm, and the 2 cm flowers have very good color. I've found the plant difficult to bloom and this is only the second flower I've had on it. It requires cool to cold temperatures and I am providing that, but learned recently that it likes to be dried out a bit in the winter, so I'll have to do that and see if it produces more flowers then.
