Don't make the mistake I did and upgrade more than 1 love tree.
Despite that each tree has to be upgraded individually, (at a cost of 3000 flowers to reach the 3rd level), when one tree is used they ALL go on cooldown, so you can only use 1 tree each 1d 16h if you have 3 of them. The other 2 trees (which are also significant flowers to get in the first place) ONLY help with cooldown.
This is hardly fair, but then, what is? If they're upgraded individually, you'd hope that you could use 3 at one time. Luckily I tested it before doing more upgrades, so I "only" wasted 2000 flowers which I will obviously not get back.
So only upgrade 1, you can move it easy enough to what you want to buff. The nice part is it's a "small" tree and goes more or less anywhere.