When it comes to enriching your outdoor plant boxes with calcium, choosing the right plants is key. Calcium is essential for strong cell walls, healthy root development, and overall plant vitality. Here are some of the best plants known for their ability to accumulate calcium in outdoor plant boxes:

1. Comfrey (Symphytum officinale) – A dynamic accumulator, comfrey pulls calcium from deep in the soil and stores it in its leaves, making it an excellent choice for composting or mulch.

2. Kale (Brassica oleracea) – This nutrient-dense leafy green not only provides edible benefits but also helps improve calcium levels in the soil.

3. Nettles (Urtica dioica) – Often considered a weed, nettles are fantastic for accumulating calcium and other minerals, enriching the soil naturally.

4. Alfalfa (Medicago sativa) – A deep-rooted plant that fixes nitrogen and absorbs calcium, making it ideal for improving soil fertility.

5. Dandelions (Taraxacum officinale) – Their long taproots draw up calcium from subsoil layers, benefiting nearby plants.

To maximize calcium accumulation, consider interplanting these species with other garden plants or using their leaves as mulch. Regular soil testing can also help monitor calcium levels and ensure optimal plant health. Happy gardening!