A tree for each child, planted from the seed of the parent’s trees.  When the child is old enough and selects a mate, the ceremony includes transplanting the two saplings together in a special garden, and the two intertwine and produce plenty of fruit that can be enjoyed by both humans and dragons.  For girls, their tree is Companionship – for boys, their tree is Commitment.  Once the trees are joined, the ideas of Companionship & Commitment become gender neutral, and the fruit becomes plentiful, sweet, and healthy.  This is of course what’s best…then there’s what’s possible…

 It is possible for the dragons to eat the little bit of fruit that comes from an unjoined tree – doing this weakens the tree, and the fruit is bitter, making the human sick.  (the dragons, however, clamor for this fruit, at increasingly younger ages – many villagers agree that it is best to just give the dragon what it wants to keep it calm) 

 It is also possible for someone to cut one portion of a united tree, at the root, destroying the union and making the fruit less plentiful/sweet/healthy.  (they will have destroyed either the companionship or the commitment – it is also possible to chop down the whole tree).  It is possible for the living portion of a united tree to be joined to another tree, sort of – they’re not saplings anymore, so the intertwining is a little tougher, and the scars of the previous union are visible in the bark.

 It is possible to join two Companion trees, or two Commitment trees, but again the fruit has an off taste, isn’t as plentiful, isn’t healthy, and of course doesn’t provide new saplings. 

 Walking through the garden, villagers can see the different trees and the shapes of the intertwinings – some areas of the garden are brighter and more beautiful, some are a bit spooky.  Each tree pair is tended by its couple, and there are ancient scrolls with the lore of the trees on them, but they tend to be ignored as outmoded ways, too difficult, etc.