Clover can be seeded by broadcasting onto snow in late winter–February or March in Massachusetts. The freeze thaw cycle works the seed into the soil so that it can germinate when things warm up. Frost seeding clover by drone works well because the application rate, 10 lbs per acre, is light. Drone seeding can be done when fields are too wet to work with a tractor. And why run a tractor over the land when such a light seeding rate is required?