Hi ntnete0! For this year's Spring Event, Cherry Trees are marked as Incidents that can occur in your city and, therefore, there could be times where you will get some Cherry Trees in your city for a given day, as well as times where there will not be any Cherry Trees at all...but, fear not! You do not need those extra Cherry Trees to ensure that you can get your hands on a Level 7 Pagoda; all you need to do is to complete each and every Quest and to log in at least once a day to collect your extra Lanterns and you will be rewarded with a nice Level 7 Pagoda at the end of the Event!
Those Cherry Trees are like a bonus for FoE players, so keep you eyes peeled!