Arranging annuals in an outdoor plant box can transform your garden into a colorful paradise. The key is to consider factors like color harmony, plant height, and spacing for a balanced look.

1. Color Coordination: Choose a color scheme that complements your outdoor space. Monochromatic themes create elegance, while contrasting colors add vibrancy. For example, pair purple petunias with yellow marigolds for a striking effect.

2. Height Variation: Place taller annuals like snapdragons or salvia at the back of the box, medium-height plants like zinnias in the middle, and trailing varieties like lobelia or sweet alyssum at the front for a cascading effect.

3. Spacing: Avoid overcrowding by following planting guidelines. Most annuals need 6-12 inches of space to thrive. Proper spacing ensures healthy growth and prevents disease.

4. Sunlight Requirements: Group plants with similar light needs. Sun-loving annuals like geraniums and verbena should share a box, while shade-tolerant impatiens and begonias can be planted together.

5. Seasonal Interest: Mix early, mid, and late-blooming annuals to keep your plant box lively throughout the season. For example, combine pansies (spring) with cosmos (summer) and chrysanthemums (fall).

With these tips, your outdoor plant box will become a focal point of your garden, bursting with color and life all season long!