Yes, you can grow dwarf horseradish plants in an outdoor plant box! Horseradish is a hardy perennial that thrives in containers, provided you meet its basic needs. Here’s how to ensure success:

1. Choose the Right Container: A deep plant box (at least 12 inches) allows room for the taproot to develop. Ensure proper drainage to prevent waterlogging.

2. Soil Requirements: Use well-draining, fertile soil with a slightly acidic to neutral pH (6.0–7.0). Mix in compost for added nutrients.

3. Sunlight: Horseradish prefers full sun but tolerates partial shade. Aim for at least 6 hours of sunlight daily.

4. Planting: Plant root cuttings or crowns 2–3 inches deep, spacing them 12–18 inches apart. Water thoroughly after planting.

5. Care Tips: Keep the soil consistently moist but not soggy. Mulch to retain moisture and suppress weeds. Fertilize lightly in spring.

6. Harvesting: Dwarf horseradish matures in 4–6 months. Dig up roots in fall or early spring for the best flavor.

With proper care, your outdoor plant box can yield a robust horseradish harvest. Happy gardening!