Games : What is the mininum number of normal trees that still allow all the daily spawnables to appear?

I'd imagine I could find out if I chop every tree down in my town, then buy a sapling from Leif and plant one tree a day, and then shake every adult tree every day until I get the same amount of stuff two days in a row. After that I'd just have to chop an adult tree down and the three growing trees.