Nutational rheotropism, the fascinating phenomenon where plants exhibit slow, spiral movements in response to environmental stimuli, can be beautifully observed in outdoor plant boxes. To showcase this natural behavior, certain plants are more effective due to their growth patterns and responsiveness.

1. Climbing Beans (Phaseolus vulgaris): These fast-growing plants exhibit pronounced nutational movements as they search for support, making them ideal for demonstrations.

2. Morning Glory (Ipomoea purpurea): Known for their twining stems, morning glories display clear rheotropic movements as they climb trellises or other structures.

3. Sweet Peas (Lathyrus odoratus): Their delicate tendrils actively move in spirals, perfect for observing nutation in confined spaces like plant boxes.

4. Hops (Humulus lupulus): A vigorous climber, hops exhibit strong nutational growth, especially when trained vertically.

5. Passionflower (Passiflora spp.): With their rapid tendril movements, passionflowers vividly demonstrate rheotropism in outdoor settings.

For optimal results, ensure your plant boxes receive ample sunlight and provide lightweight supports like thin poles or strings. Regular watering and monitoring will enhance the plants' natural movements, offering a captivating display of nutational rheotropism in your garden.