One of the first things that might strike you about this plant is its glossiness, both dry and wet. In fact, dry plants are often easier to identify, because the shoots are smooth and look a little like brown glossy worms.
Habitat is often a good pointer to this species – it is calcicolous (a bit less so than P. platyphylla) and so is rarely found in the same places as P. obtusata, another shiny species of dry rocks.
Other than P. pinnata, all of our Porella species have a distinctive aroma (when fresh). This doesn’t help much with the identification of P. arboris-vitae, but if in doubt, try the taste test. Find a clean shoot (or clean some with water to wash off dirt) and nibble a small piece. Only P. arboris-vitae responds to such treatment with an acrid peppery after-bite.Read the Field Guide account