Growing a small redbud tree in an outdoor plant box is possible, but it requires careful consideration of the tree's needs and the container's limitations. Redbud trees (Cercis canadensis) are known for their stunning spring blooms and compact size, making them a popular choice for urban and small-space gardens.

Key Factors to Consider:

1. Container Size: A redbud tree needs ample root space. Choose a plant box at least 24 inches deep and wide to accommodate growth.

2. Drainage: Ensure the box has proper drainage holes to prevent root rot.

3. Soil Quality: Use well-draining, nutrient-rich soil to support healthy growth.

4. Sunlight: Redbuds thrive in full sun to partial shade—place the box in a spot with at least 6 hours of sunlight daily.

5. Watering: Container trees dry out faster than ground-planted ones. Water regularly, especially during hot weather.

While a redbud tree can adapt to a plant box, it may eventually outgrow it. Transplanting to a larger container or the ground may be necessary as the tree matures. With proper care, your redbud can flourish in an outdoor plant box, adding beauty to patios, balconies, or small gardens.