A flea problem can be frustrating. They make you itch, they're nearly too small to see, and they seem to be everywhere -- even in your garden. However, even though they're small, it's relatively easy to get rid of fleas in dirt. But first, eliminate the source of the problem. Fleas never stray too far from their animal hosts. Fleas in the dirt around your house indicate that it's time to take your pet to the vet or guard your garden from stray invaders. Otherwise, the fleas will just keep coming back.
Expose as much of the dirt to the sun as possible. Fleas prefer moist, shady areas. You'll likely want to keep your plants, but any weeds, plant debris or other non-essential items should go. Also consider replacing any organic mulch in your garden with cedar mulch. It will serve the same purpose, but fleas are not fond of its smell.
Introduce nematodes into your garden. Nematodes are tiny worms that feed on flea larvae. They will not eat adult fleas, but they can interrupt the reproductive cycle if the fleas are laying their eggs in your garden. Products available at your local garden supply store can be mixed with water and sprayed onto the affected dirt according to the packaging instructions.
Sprinkle food-grade diatomaceous earth (DE) over dry dirt. DE is composed of the sharp, fossilized remains of hard-shelled algae. When adult fleas come into contact with it, the sharp edges of the fossils penetrate their exoskeleton and dehydrate them in a matter of days. This product is quite safe, and can even be sprinkled on your pet or in the house if the flea problem has spread. However, wear a dust mask when applying it. The tiny, light particles are easy to inhale.