I have had a lot of trouble with Oncidium Alliance hybrids for 2 reasons.
1. Most of these are mass produced in places like Taiwan, grown too fast and forced to bloom too early. To speed things up they are provided very specific conditions for each phase of development that we can not duplicate in the house. So unless you buy from a grower who grows for people interested in keeping their plant even after the pretty centerpiece fades, your plant may have to make a major shift in the way its genetic programs are expressed to cope with a new environment the likes of which it has never seen before. At best- all this takes time.
2. Some will only grow well if you can keep temperatures 55-85 F. Many times I can find recommendations the people at Orchidworks provide for their growers. They are American growers in Hawaii who sell plugs they produce, wholesale. If they don't say the plant can be grown warmer than intermediate I don t buy it.
The Orchid Works
Click on Click on Plant Archive or Current List and find out recommended growing conditions for the growers
You are in luck with Dart Vader:
P140 Mtssa. Dark Star 'Darth Vader'
General Requirements
Temperature 55 - 90 Degrees Farenheit
Humidity 50% - 80%
Light 3000 foot candles
Balanced fertilizer (6N-2P-4K-2Ca-1Mg) @ 100-150ppm of nitrogen
This is one of those plants that will withstand just about anything. A good choice for South Florida summers. It has great color, size and general eye appeal. This is the progeny of Mtssa. Charles M. Fitch which has been a standard for over 20 years