Bring more Oak Veterans and Giants!
There are several mosshearts which spawn in a semicircle around the Giant Jungle wurm location in Caledon forest, as well as spread throughout the rest of the jungle… in addition to the populations of oakhearts/mosshearts you can find all over the rest of tyria.
I feel that the amount of ‘plants’ is actually ok as it is.
Giants on the other hand are another story…
There are only a handful of giants in the world, two of which are hostile, and neither of which give any loot worth the ten minutes it takes to kill one (by yourself anyway).
I would hope that anet eventually gives players a reward for killing them, or places more of them throughout tyria.