Nutational hydronasty is a fascinating plant movement phenomenon where plants exhibit growth responses to environmental stimuli like light, moisture, or gravity. If you're looking to observe this in outdoor plant boxes, certain species stand out for their pronounced and visually striking movements.

1. Mimosa pudica (Sensitive Plant) – Known for its rapid leaf-folding response to touch, this plant is a classic example of hydronasty. Its delicate leaves react to physical contact, making it a captivating choice for outdoor displays.

2. Oxalis triangularis (Purple Shamrock) – This plant demonstrates nyctinasty, a subset of hydronasty, by folding its leaves at night and reopening them in daylight. Its vibrant purple foliage adds aesthetic appeal to plant boxes.

3. Maranta leuconeura (Prayer Plant) – With leaves that rise and fall in a daily rhythm, this plant is perfect for showcasing nutational movement. Its patterned leaves also enhance visual interest.

4. Dionaea muscipula (Venus Flytrap) – While famous for its snap-trap mechanism, it also exhibits subtle hydronastic movements in response to prey and environmental changes.

5. Helianthus annuus (Sunflower) – Sunflowers display nutation as they track the sun (heliotropism), making them ideal for observing directional growth in outdoor settings.

For optimal results, ensure your plant boxes receive adequate sunlight and moisture. These plants not only demonstrate hydronasty but also create dynamic, ever-changing garden displays. Observing their movements can deepen your appreciation for plant adaptability and natural beauty.