If you're looking to create a thriving outdoor plant box in iron-rich soil, selecting the right plants is crucial. Iron-accumulating plants not only tolerate high metal concentrations but also help detoxify the soil. Here are some top choices for your garden:

1. Sunflowers (Helianthus annuus) – These vibrant flowers absorb heavy metals like iron while adding a splash of color.

2. Indian Mustard (Brassica juncea) – A fast-growing plant known for its ability to extract iron and other metals from the soil.

3. Spinach (Spinacia oleracea) – Surprisingly effective at accumulating iron, making it both edible and functional.

4. Ferns (Pteris vittata) – Also called the "brake fern," this plant excels at absorbing iron and other heavy metals.

5. Alfalfa (Medicago sativa) – A deep-rooted plant that improves soil quality while accumulating iron.

For best results, pair these plants with well-draining soil and regular watering to prevent metal toxicity. Happy gardening!