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.
The mininum number of normal trees that still allow all the daily spawnables to appear
animal-crossing-new-leaf
Best Answer
Well, according to the this guide I found that for New Leaf they report that each day, 20 trees produce bells, 2 trees produce furniture and 5 trees have beehives.
But since furniture, beehives and bugs can also fall from non-fruit trees, I guess you would need to have at-least 30 trees. I've never seen an exact counting as it probably varies from day to day due to the random nature of the non-bell drops.