One natural way of controlling fleas that people have used is to put plants in their garden or yard that ward off fleas. It sounds weird, but many plants have natural pesticides as a defense mechanism, and there are a few that you can use to keep your yard and garden flea-free.
First is lavender. Lavender actually got a reputation in the middle ages as a cure for the plague. This was simply because it kept fleas away, and it was used as a scent on clothing. So the people who used it didn’t get bitten and didn’t catch plague from the fleas. Lavender is generally not toxic to dogs or cats.
Second is eucalyptus. You can often get the branches at craft stores if you don’t want the whole plant. They are known as plants that work as flea repellants. BUT – they are generally listed as poisonous to both cats and dogs. So I do not recommend using them.
Third is mint. This is traditionally considered a way to get rid of fleas, and it is safe for cats and dogs (it’s related to catnip).
You should know that putting these plants in your garden or yard may deter fleas from coming in, but it isn’t a cure-all. It won’t keep them off your pet or out of your house, so you’ll have to do something else about that.