Garden Q&A: Red cap lichen and what to use to make raised garden beds
By Ellen Nibali
Jan 02, 2020 | 7:00 AM
Found these guys growing on some very old firewood. Mushrooms? They’re stiff and short, like bristles.
These are red cap lichen, commonly called British soldier lichen, because their red caps are reminiscent of those worn by red coats — British soldiers — during the Revolutionary War. The caps are the sexual fruiting bodies of the lichen, perched on the ends of its gray-green stems.
Lichen are part fungus and part plant, living in mutualistic symbiosis, meaning both benefit from the arrangement. The plant’s chlorophyll creates nourishment while the fungi absorbs water and nutrients. Often you see lichen on an organic surface, for example, a tree trunk, as a support but, as you’ve found, Cladonia cristatella can be on stumps, logs or fence rails in the sun. As wood ages, it can becomes almost sponge-like holding water, thus good for lichen. These lichen reproduce primarily from broken fragments or spores. They work well in terrariums due to their diminutive 1” size.
This spring I plan to buy treated lumber for raised vegetable beds. Please give me a heads up on treatment options of lumber. CCA is out. ACQ is supposed to be somewhat safe.
CCA treated wood is no longer available for residential use as of 2004. The relatively new chemical treatment ACQ (alkaline copper quaternary) is safe to use in food gardens. Some of the copper may leach over time from the lumber, but the risk to human health is considered to be low. From research we have seen, a toxic level of copper would kill the plants before the edible fruit, roots, or plants would be harvested.
If you still have doubts, select a different material such as brick, stone, and untreated or plastic lumber. You can forego any enclosure by mounding soil 4-6 inches above grade, leveling the top and sloping the sides. Search the Home and Garden Information Center’s website for materials for building raised beds.
University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.