Sick orchid - leaves turned yellow and dropped off after re-potting

[SouthPark]

lemonslice - Roberta also asked what sort of pot you use ---- and asked if it has good drainage.

Good drainage (enough holes on the bottom of it) is good for the plant. It allows water to drain right out, and also allows air to flow through the pot - provided that the media is airy enough to allow for good air-flow. Good air-flow across the roots and through the media in the pot is beneficial to the health of the plant.

So - to give the orchids growing conditions:

1. good drainage pot (maybe with a grate or stand so that the bottom of the pot doesn't get the holes blocked by whatever the pot rests on).

2. airy media that doesn't become water logged, but allows some moisture to be retained during watering ..... eg. scoria or bark pieces ------ but the bark pieces need to be suitable for orchids - not ones that might contain chemicals or compounds that could kill an orchid. Eg. a lot of growers use 'Orchiata bark'. The choice of media size needs to match the size of the roots. If the pieces are too small - waterlogging can occur. Too large, and the roots might not get enough contact with the media, and the plant dehydrates and dies slowly.

3. comfortable temperature for the orchid - should be maintained.

4. suitable light level and duration are required.

5. good air-flow around the whole plant (leaves, stem, roots, media) ----- avoid still-air growing environments. Still-air invites certain unwanted issues - certain unwanted fungus, and can also get in the way of good water/oxygen movement through the pot across the roots and media.

In your case - maybe your pot is not good draining. And maybe you haven't had good air-flow (eg. movement of air by breeze and/or fan). Or - as Roberta mentioned - that particular type of bark may be poisoning the orchid.

Another thing is - dry bark won't easily get wet unless it's being bombed by water for a relatively long time. Water runs straight off dry bark, as very dry bark repels water. So this needs to be considered. If the pot stays 'light' after watering - it can mean that the bark hardly absorbed any water. If this happens - the plant won't get much or any water into it, and can die slow - as in yellowing leaves, and dropping leaves.