I really like the idea of a tree planting ceremony instead of the boring old unity candle. The couple waters the tree, then takes it home and plants in their yard. Just as the plant grows, so too will their love grow with time. Either dirt or water.
TOH: How to Plant a Tree - the PROPER way. [Surprisingly, tree planting is often done incorrectly, says Roger. "I see improperly planted trees all the time, many of them put in by professional landscapers.