I think the only way is to cancel the beautiful town ordinance for a day, leave a rotten turnip or a piece of candy on the ground, and wait for ants and flies to swarm it. Then, you can turn on the ordinance again for 20,000 bells. Only four flowers wilt per day, and you can revive them that day by watering them. I think that's the only way to do it.
If you time travel, it could go much quicker, but it carries a lot of risks if not done properly.