This is a dwarf sheffelera that had been trained for many years as bonsai, then planted inside the rock. They sell these at the airports and several stores across Hawaii. They all come from the same source, Fuku Bonsai located on the big island of Hawaii. I have visited here, and it is what started me down the road of bonsai. Here is a link to their site and more info about these trees and how to care for them. The owner David has done some amazing work with sheffelera bonsai and my local bonsai instructor here in PA knows him well and has fond respect for him and what he is doing. The class I took with there in Hawaii does recommend to water for 30 minutes so the water can fully penentrate all the pours of the rock and pull in fresh oxygen when removed. I'd follow what David suggests for this Bonsai.
www.fukubonsai.com