Arranging endangered plants in an outdoor plant box requires careful planning to ensure their survival and growth. Start by selecting a location with the right sunlight and shade balance, as many endangered species have specific light requirements. Use high-quality, well-draining soil mixed with organic matter to provide essential nutrients. Group plants with similar water and soil needs together to simplify care. Incorporate native plants to support local ecosystems and attract pollinators. Regularly monitor soil moisture and protect the plants from extreme weather. By following these steps, you can create a thriving outdoor plant box that helps conserve endangered species while enhancing your garden's beauty.