Oncidium not doing well..Leaves dropping

[cass2828]

Hi guys... My oncidium is not doing well.its leaves are turning black from the leaf and dropping off

[estación seca]

Hi cass2828, that looks like either sunburn, water with too many minerals dissolved in it, too hot temperatures or not enough water.

It's in large bark and the bark looks dry, so I'm going to guess you might not be watering often enough and this might be an Oncidium that doesn't tolerate much heat. You previously said you're in south India, where it's warm. Oncidiums would need a lot of water when it's warm. And I would try to keep it in a cooler spot but still with bright shade.

[cass2828]

Mmm I guess my water is too hard for the plant..

[Dollythehun]

Every oncidium seems to take different tds. I agree with ES. From my oncidiums, too hard, too little, but it's a water problem, not rot.

[Roberta]

If water is hard, you can compensate somewhat by flushing well (water until it runs out of the pot) This keeps salts from building up. With the exception of some cloud forest species that can be quite picky, most orchids (especially the more commonly-purchased hybrids) will tolerate pretty nasty water, depending on the mineral content. (If high in calcium they'll tolerate a lot more than if high in sodium, for instance)

[Tommyr]

Since I collect rain water for my carnivorous plants I also use it on my orchids and other house plants. Rainwater is the best source, nearly zero total dissolved solids. Usually 2ppm.