There's no limit that I know of, besides however many can actually fit of course. (I don't think there's a perfect fruit tree limit either?)
Sometimes trees/bushes can die if too many are planted at once in the same area, or where they're too closely surrounded by other plants, but you can almost always get around this by planting them one row at a time (like from left to right or top to bottom -- this gives them room to breathe as they grow). Oh and you can't have more than 12 bushes/trees connected in a chain (think this rule's common knowledge, but just in case). Flowers of course have no arbitrary planting rules so you can stuff your town to the brim with em if you want.