Now imagine an orchid in its native tropical rainforest environment. It is hot and humid, you spot an orchid which is growing from the crevice of two tree branches. Upon closer look you see its roots have wrapped around the trunk and leaf debris has fallen into the branch crevice creating a small nest of moisture retention for the orchid roots (aka your moss/bark mix). The sun beams break through the tree canopy above, basking the orchid for brief moments with light. When it rains, the rain trickles down the tree trunk running over the orchid roots that absorb bits of each drop as they pass. At the same time, water catches in the orchid leaves and are directed down into the roots. The orchid roots never stay too wet, they are usually put through a dry spell between rain showers. They do however have the luxury of absorbing moisture through the humid air and the leftover moisture that the tree bark has absorbed during the last rainfall.