Haptotropism, also known as thigmotropism, is the fascinating growth response of plants to touch or physical contact. Outdoor plant boxes provide an excellent environment to observe this phenomenon. Here are some of the best plants to showcase haptotropism:

1. Climbing Plants:

- Sweet Pea (Lathyrus odoratus): This fragrant climber wraps its tendrils around supports, making it perfect for demonstrating haptotropism.

- Morning Glory (Ipomoea purpurea): Known for its rapid growth and twining stems, it responds quickly to touch.

2. Touch-Sensitive Plants:

- Mimosa pudica (Sensitive Plant): While not a climber, its leaves fold inward when touched, offering a dramatic display of haptotropism.

3. Vining Vegetables:

- Cucumbers (Cucumis sativus): Their tendrils grasp supports tightly, showcasing strong haptotropic responses.

4. Ornamental Climbers:

- Clematis: This flowering vine uses leaf stems to cling to structures, ideal for outdoor plant boxes.

For optimal results, provide trellises or supports in your plant boxes to encourage these plants to exhibit their natural haptotropic behaviors. Observing these plants can be both educational and visually rewarding for any gardening enthusiast.