Arranging indigenous plants in an outdoor plant box is a fantastic way to create a sustainable, low-maintenance, and visually appealing garden. Start by selecting native species that thrive in your local climate, ensuring they require minimal water and care. Group plants with similar sunlight and soil needs together, placing taller species at the back and shorter ones in front for a layered effect. Incorporate a mix of textures and colors to enhance visual interest, and leave enough space between plants to allow for growth. Finally, add mulch to retain moisture and suppress weeds, completing a beautiful and eco-friendly plant box arrangement.