If properly designed and maintained, rain gardens should not attract mosquitoes. Mosquitoes need standing water for at least 7 to 12 days to breed. A well-designed rain garden should allow water to infiltrate the ground within 24 to 48 hours, well before mosquitoes could breed. However, if water stands in the garden for longer periods due to poor design or drainage issues, it could potentially become a breeding ground for mosquitoes.