If you're looking to grow selenium-accumulating plants in an outdoor plant box, you'll want to choose species that naturally thrive in selenium-rich soils. These plants not only absorb selenium efficiently but also add unique beauty and health benefits to your garden.

1. Indian Mustard (Brassica juncea): This fast-growing plant is a top choice for selenium accumulation. Its leaves and stems absorb high levels of selenium, making it ideal for phytoremediation and edible gardening.

2. Sunflower (Helianthus annuus): Sunflowers are not only vibrant and easy to grow but also excellent at extracting selenium from the soil. Their deep roots help them access nutrients effectively.

3. Astragalus (Astragalus bisulcatus): Known as "locoweed," this plant is a selenium hyperaccumulator. It’s perfect for gardeners interested in studying selenium’s role in plant health.

4. Broccoli (Brassica oleracea): Broccoli accumulates selenium in its florets, offering a dual benefit of nutrition and soil enrichment. It’s a great addition to any edible garden.

5. Garlic (Allium sativum): Garlic absorbs selenium efficiently, enhancing its health benefits. Planting garlic in your outdoor box can yield flavorful, nutrient-rich bulbs.

Tips for Growing Selenium-Accumulating Plants:

- Test your soil’s selenium levels before planting.

- Ensure proper drainage to prevent selenium toxicity.

- Rotate crops to maintain soil health.

By selecting these plants, you can create a thriving, selenium-rich garden that’s both functional and visually appealing. Happy gardening!