Arranging perennials in an outdoor plant box requires thoughtful planning to create a visually appealing and thriving garden. Start by considering the height of each plant—place taller perennials like delphiniums or hollyhocks at the back, medium-height plants such as lavender or salvia in the middle, and low-growing varieties like creeping thyme or sedum at the front. This layered approach ensures all plants receive adequate sunlight.

Next, focus on color harmony. Group complementary or contrasting colors for impact, or opt for a monochromatic scheme for elegance. Pay attention to bloom times to ensure continuous color throughout the seasons. For example, pair early bloomers like bleeding hearts with late-season flowers like asters.

Spacing is crucial to avoid overcrowding. Follow the recommended spacing for each perennial to allow room for growth and airflow, reducing disease risks. Incorporate evergreen or foliage plants like hostas for year-round texture.

Finally, consider maintenance needs. Group plants with similar water and sunlight requirements together for easier care. With these tips, your outdoor plant box will become a vibrant, long-lasting garden centerpiece.