Crystallotropism, a fascinating plant movement response to crystalline structures or directional stimuli, can be beautifully observed in outdoor plant boxes. Certain plants excel at showcasing this phenomenon, making them ideal for educational or decorative purposes.

1. Sunflowers (Helianthus annuus): Known for their phototropism, sunflowers also exhibit crystallotropism by aligning their stems and leaves toward reflective surfaces or light-diffracting objects. Their large, vibrant blooms make them a striking choice.

2. Morning Glories (Ipomoea purpurea): These climbers respond to crystalline structures by twining around them, demonstrating how plants use environmental cues for growth. Their rapid growth and colorful flowers add charm to any setup.

3. Bean Plants (Phaseolus vulgaris): With their tendrils and leaves sensitive to light reflections, bean plants subtly adjust their growth toward crystalline or reflective surfaces, making them excellent for demonstrations.

4. Passionflowers (Passiflora spp.): Their intricate vines and leaves often orient toward light-refracting objects, showcasing crystallotropism in a visually appealing way.

5. Climbing Roses (Rosa spp.): While primarily phototropic, some varieties also respond to crystalline stimuli, making them a versatile choice for outdoor plant boxes.

For optimal results, place reflective or crystalline objects near these plants and observe their gradual movements. This not only highlights plant adaptability but also creates a dynamic, ever-changing garden display.