Epinasty is a fascinating plant response where leaves or stems curve downward due to environmental stress, often caused by factors like excess water, pathogens, or ethylene exposure. If you're looking to observe this phenomenon in outdoor plant boxes, certain plants are more likely to exhibit epinasty clearly.

1. Tomatoes (Solanum lycopersicum) – Tomatoes are highly sensitive to ethylene and waterlogged soil, making them ideal for demonstrating epinasty. Overwatering or poor drainage can quickly trigger this response.

2. Petunias (Petunia spp.) – These popular ornamental plants often show epinasty when exposed to ethylene gas or root stress, making them a great choice for visual observation.

3. Impatiens (Impatiens walleriana) – Known for their delicate leaves, impatiens can display pronounced epinasty under excessive moisture or fungal infections.

4. Eggplants (Solanum melongena) – Like tomatoes, eggplants are part of the nightshade family and react strongly to ethylene and water stress, showcasing noticeable leaf curling.

5. Peppers (Capsicum annuum) – Pepper plants may exhibit epinasty when overwatered or exposed to ethylene, providing a clear example of this stress response.

To observe epinasty, ensure your plant boxes have controlled conditions—such as varying water levels or ethylene exposure—while monitoring plant reactions. This not only helps in studying plant physiology but also improves gardening practices by identifying stress triggers early.

By selecting these plants, you can effectively demonstrate and study epinasty in an outdoor setting, enhancing both your gardening knowledge and experimental observations.