The two exp are not related at all.

Level up exp is gained when YOU water OTHERS and yourself

reward exp is gained when OTHERS or you water it.

So you could be gaining 0 level up exp a day if you don't do any watering yourself yet still claim the reward if there are enough watering the tree for you.

Also, level up exp is 1 exp per watering, always. Whereas the reward exp is tied to friendship level and you can get up to 3 for a single watering.

Edit: sometimes you can view the tree of others, are you sure it is YOUR tree that is lv 8?

Also, have you checked how much exp your tree have? hover your mouse over the level and it will tell you.

Yes and read what i wrote I said i water peoples tree everyday, I always water max peoples trees until i can't water peoples tree anymore. Instead of trying to pick holes into me why don't you accept what i said and admit there is a problem. People in my group have logged in less than me missing some days and are still level 8 trees while I have not missed a single day in this game and have watered every single day max times I was able to do so.

Also just so you know if you claim the reward you can still water peoples trees. by clicking the x *on and it then brings you to your friends trees that allow you to water them.