Yes, you can grow dwarf plum trees in an outdoor plant box! Dwarf plum trees are ideal for container gardening, as their compact size makes them perfect for small spaces like patios, balconies, or urban gardens. Here’s how to ensure success:

1. Choose the Right Variety: Opt for dwarf or semi-dwarf plum tree varieties, such as 'Starkrimson' or 'Dwarf Santa Rosa,' which thrive in containers.

2. Select a Suitable Plant Box: Use a large, sturdy container (at least 18-24 inches in diameter) with good drainage to prevent root rot.

3. Soil and Sunlight: Plant in well-draining, nutrient-rich soil and place the box in a spot that receives 6-8 hours of sunlight daily.

4. Watering and Fertilizing: Keep the soil consistently moist but not waterlogged. Fertilize with a balanced fruit tree fertilizer during the growing season.

5. Pruning and Care: Regularly prune to maintain shape and encourage fruit production. Protect the tree from extreme weather by moving the box if necessary.

With proper care, your dwarf plum tree can yield delicious fruit while adding beauty to your outdoor space. Happy gardening!