Creating an outdoor plant box with an ER bridge theme combines functionality and aesthetics, offering a unique way to enhance your space. The best plants for this setup are those that thrive in shaded or partially shaded environments, as bridges often limit direct sunlight.

1. Ferns: Ideal for shady spots, ferns like the Boston Fern or Maidenhair Fern add lush greenery and require minimal maintenance.

2. Hostas: Known for their striking foliage, hostas are perfect for shaded areas and come in various colors and sizes.

3. Heuchera (Coral Bells): These plants offer vibrant foliage and tolerate shade well, adding a pop of color to your plant box.

4. Ivy (Hedera): A classic choice for vertical growth, ivy can cascade beautifully from the plant box, creating a natural, flowing effect.

5. Begonias: These flowering plants thrive in partial shade and provide bright blooms throughout the season.

For low-maintenance options, consider succulents like Sedum or Sempervivum, which can tolerate varying light conditions. Pairing these plants with decorative elements like small rocks or miniature bridge replicas can enhance the ER bridge theme.

By selecting plants that suit the light and moisture conditions of your outdoor plant box, you can create a visually appealing and sustainable display that complements your ER bridge theme.