Every two collected will automatically create as many healing syringes as you have space for in your syringe bag. Every one collected if you have the Harvester skill, which is one of the better ones to get at the start of the game.
Note however that although Green Leaf items stack in one slot, the loot bag goes by number of items, so you can run out of space fast early on when your loot bag isn't upgraded very far if you collect too many Green Leafs.
One thing my buddy did that was intereseting was put the garden in at the Ghale family estate and it only has crafting supplies. So he uses alot of all different types of syringes (while I only use health shots), and he just runs out to the garden and takes every plant there and has a large supply that never runs out, cause the next time you fast travel there they are ll grown back.Originally Posted by Ranger_Vet68 Go to original post