Mosquitoes can turn your outdoor plant boxes into a breeding ground, but with a few simple steps, you can create an effective deterrent system. Start by eliminating standing water, as it attracts mosquitoes. Add natural repellents like citronella, lavender, or marigolds around your plant boxes. For a DIY solution, mix water, vinegar, and essential oils in a spray bottle and apply it to the soil. Installing mosquito nets or fine mesh around the boxes can also block pests. Regularly clean and maintain your plant boxes to prevent mosquito infestations. These methods will help you enjoy a mosquito-free garden all season long.