Are you related to the old guy with the flat-top haircut in Tacoma with the stark white bungalow and Astroturf yard who came out when he saw me looking at the locally very rare 'Pink Perfection' Japanese cherry street trees and asked, hopefully, if I was there to cut them down?

The fallen petals, you see, made an awful mess requiring him to get out his blower every year.

In Japan there is a tradition of having a picnic and watching the petals fall from cherry trees.

For recent related discussion...

Here is a link that might be useful: Can you prevent fruit from forming - UBC Botanical Garden Forums

This is just a suggestion, but I think it might be easier just to get rid of the tree altogether if you're not wanting the blooms or the fruit.

-Audric

I, for one, can understand the problem. It's all about location of the trees, which I expect he enjoys for the most part. There is nothing odd about someone wishing to do something about a messy fruit when the trees in question are located over a side walk, or patio, porch, parking area.

I'm afraid that there isn't a household product that will do what you want it to. But, as mentioned in another forum, you can purchase Florel, which will work nicely. However, Florel applications need to be timed just right or you will be wasting your time and money.

It might be helpful to see if there is someone at the local extension office who can help you will this issue (timing).

Regarding Florel, see end of discussion at my link (above).

Florel is a great idea. It is a wonderful product that causes irritation to nasal passages and lungs. Its toxicity is unknown to birds. But you are only spraying two trees, it shouldn't have any effect on the birds.