Hydronasty, the movement of plants in response to water, is a fascinating phenomenon that can add dynamic beauty to outdoor plant boxes. Certain species are particularly adept at showcasing this trait, making them ideal choices for gardeners who want to observe nature's responsiveness up close.

1. Mimosa pudica (Sensitive Plant): Known for its rapid leaf-folding reaction to touch or water droplets, this plant is a classic example of hydronasty. Its delicate foliage curls inward when wet, creating a striking visual effect.

2. Dionaea muscipula (Venus Flytrap): While famous for trapping insects, this carnivorous plant also exhibits hydronasty by closing its traps when stimulated by water, such as rain.

3. Oxalis triangularis (Purple Shamrock): Its leaves fold downward at night or when exposed to excess moisture, demonstrating a subtle but elegant hydronastic response.

4. Maranta leuconeura (Prayer Plant): This tropical plant raises and lowers its leaves in response to humidity changes, making it perfect for humid outdoor boxes.

5. Neptunia aquatica (Water Sensitive Plant): Similar to Mimosa, its leaves collapse when wet, offering a dramatic display of hydronasty.

For optimal results, place these plants in well-draining soil and monitor moisture levels to encourage their natural movements. Incorporating hydronastic species into outdoor plant boxes not only enhances visual interest but also provides an educational glimpse into plant behavior.