Yes, you can use an outdoor plant box to grow plants specifically for natural leather tanning. Many traditional tanning plants, such as oak galls, sumac, and willow bark, thrive in containers or raised beds, making them ideal for small-scale DIY projects.

An outdoor plant box offers controlled conditions, allowing you to cultivate tannin-rich plants efficiently. Ensure the box has proper drainage and sunlight exposure, as these plants often prefer well-drained soil and partial to full sun.

Popular plants for leather tanning include:

- Oak (Quercus spp.): High in tannins, oak bark and galls are staples in traditional tanning.

- Sumac (Rhus spp.): Leaves and bark provide strong tanning properties.

- Willow (Salix spp.): Bark contains salicylic acid, useful for both tanning and medicinal purposes.

Growing these plants in an outdoor box also helps you avoid chemical treatments, aligning with eco-friendly tanning practices. Harvest the bark, leaves, or galls when mature, then process them into a tannin-rich solution for soaking hides.

With patience and care, an outdoor plant box can become a sustainable source for natural leather tanning, blending gardening with traditional craftsmanship.