Yes, you can grow a small redbud tree in an outdoor plant box, but it requires careful planning and proper care. Redbud trees (Cercis canadensis) are known for their stunning pink or purple spring blooms and heart-shaped leaves, making them a popular choice for gardens. However, their growth in containers demands attention to a few key factors.

First, choose a dwarf or compact variety, such as 'Forest Pansy' or 'Ruby Falls,' which are better suited for confined spaces. The plant box should be large enough—at least 24 inches deep and wide—to accommodate the tree's root system. Ensure it has adequate drainage holes to prevent waterlogging.

Use well-draining, nutrient-rich soil and place the box in a spot with full sun to partial shade. Regular watering is essential, especially during dry spells, but avoid overwatering. Fertilize lightly in early spring to support growth.

Prune the tree occasionally to maintain its shape and remove dead branches. While redbuds can thrive in containers for several years, they may eventually outgrow the box and need transplanting to the ground. With the right care, your redbud tree can flourish in an outdoor plant box, adding beauty to your patio or balcony.