Nitrogen fixation is a natural process that enriches soil by converting atmospheric nitrogen into a form plants can absorb. For outdoor plant boxes, selecting the right nitrogen-fixing plants can significantly improve soil fertility and support healthier growth for surrounding vegetation. Here are some of the best options:

1. Clover (Trifolium spp.) – A fast-growing cover crop that adds nitrogen to the soil while suppressing weeds.

2. Peas (Pisum sativum) – Edible and efficient, peas fix nitrogen while producing delicious pods.

3. Beans (Phaseolus spp.) – Bush beans and pole beans are excellent choices for small plant boxes.

4. Lupins (Lupinus spp.) – These vibrant flowers not only fix nitrogen but also attract pollinators.

5. Alfalfa (Medicago sativa) – A deep-rooted plant that improves soil structure over time.

Incorporating these plants into your outdoor plant boxes ensures a sustainable, low-maintenance way to boost soil health naturally. Rotate them with other crops for continuous benefits!