Nutational hyponasty is a fascinating plant movement where stems or leaves exhibit spiral or twisting growth patterns, often in response to environmental stimuli like light or gravity. If you're looking to observe this phenomenon in outdoor plant boxes, certain plants are particularly well-suited for showcasing these dynamic movements.

1. Morning Glory (Ipomoea purpurea): This fast-growing climber is perfect for demonstrating nutational hyponasty. Its twining stems actively spiral around supports, making it ideal for observing growth patterns in real time.

2. Sweet Pea (Lathyrus odoratus): Known for its delicate tendrils, sweet pea exhibits clear nutational movements as it climbs. Plant it in a sunny spot and watch its stems twist and turn.

3. Hop (Humulus lupulus): A vigorous climber, hop plants display pronounced nutational hyponasty, with stems that spiral tightly around vertical supports.

4. Runner Beans (Phaseolus coccineus): These beans are excellent for outdoor plant boxes, as their stems actively seek supports and exhibit noticeable twisting growth.

5. Passionflower (Passiflora spp.): With its intricate tendrils and rapid growth, passionflower is another great choice for observing nutational hyponasty.

To maximize visibility of these movements, ensure your plant boxes have sturdy trellises or supports. Regular watering and ample sunlight will encourage healthy growth and more pronounced nutational behavior. Experimenting with these plants can provide both aesthetic appeal and a deeper appreciation for plant biology in your garden.