If you think a tree looks sweet you have to be certain before you bite into it. Trees are really hard, and usually pretty bitter (believe me) so if you don't want a mouthful of broken teeth, sap, and sadness, you really need to be sure it's the one before you start munching.
If you really want to be certain, and not just guess, take out your bowling (ぼう) ball and roll it as hard as you can into the tree. If its the right one it will let out a sweet smell, if it's not the tree will punch you.
Currently there are no similar looking kanji which exist in the WaniKani learning system