Trouble getting Renanthera to bloom?
The plant must be matured.It must reach a certain height depending on the parent plants. Those with storei parentage in the family tree take higher to spike, sought of 1 ft and above.
There are basically 2 types.
First type has monopodial growth like Storei and Coccinea.
The second one is shorter and and tend to be clustering and can not withstand very strong sunlight. Example Matutina and Monachica.This one can be grown hanging like Vandas.
Root system must be strong and established.Look for sign of damaged root tips.
Insect especially cocroaches like to feast on the tender root tips at night.
So are earthworms. Since roots are the main souce for fertilizer absorption any injury will have profound affect on the plant.
Types of fertilizer. When it is young use fertilizer with higher nitrogen composition. It can be organic or straight chemical base mixed by the manufaturer under various brand name. But I prefer to alternate these 2 sources.
As the plant matures shift it to fertilizer with higher phrosperous content.
Third is quality of sunlight. When newly planted locate it in a less sunny part of the garden, preferably morning sun. Try to avoid mid day or afternoon sun. If you water the plant at this hour, the water droplets on the leaves may become a magnifying glass capable to scorch the leaves surface. It is burning in the tropics at this hour especially during the hotter and drier season.
Provided all the above are met, now come the weather. This is something that we can not control if we plant it in the open air like in the tropics.
In the greenhouse condition it is possible.
Normally most of the Renantheras in my garden will spike after the raining reason followed by a hotter season.In my locallity the raining season is in November and December. Then January and February is the hotter season. At his point I can see many of my Renantheras and its hybrids starting to bloom. Therefore it require a drop in the temperature followed by an immediate rising temperature for spike to initiate.
Research has been conducted for orchids in general to bloom, it takes changes of 8 to 10 degrees Fahrenheit Height between the night and day temperatures. You can try this if you have a controlled environment or greenhouse.
Some plants especially hydrids may not flower at all even if I grow untill
6 or 7 feet.The same is also applicable to mericlones. I remembered about 20 years ago, one nursery man in our locality went to Hawaii to take a 3 weeks course in mericloning. On the way home he bought some flasks with young plants at protocorm stage. He divided the clusters, put it into hundreds of new flasks with his new mericloning recipe, mount on the shaker and generate thousand of seedlings for sale. He made money because mericlones were taking the industry by storm. I also bought 10 plants from him they all never flower. The other types I bought 30 plants. The plants flowered but bearing shorter spike with not more than 5 flowers and almost every spike ended up with rotten buds. Whereas the original plant had 11 flowers per spike earning an AM/AOS award.