I have used ice cubes before on Phalaenopsis and there has been now harm done. In the process of thawing atop the insulating shredded bark the orchids are potted in the temp does note go down enough to harm the roots. Once the melting point is reached , heat of fusion also raises the ices ambient temperature as it melts and trickles into the media. Orchids have a worldwide distribution and are found in various forms on all continents save Antarctica. To do that some of them have to be a lot more resilient than people give them credit.
