Plant 216

Selaginella species (Selaginellaceae)



Selaginella, a genus of approximately 700 species of moss-like plants, is similar in appearance to the clubmosses (e.g., Lycopodium). However, the two groups differ as the tiny leaves of spikemosses have a scale-like flap (ligule) at the base of their lower surface and they produce two types of spores.

Common names can be misleading. Spikemosses are not mosses, which lack a vascular system, but are true vascular plants. This means they have a well-developed system of specialised cells for moving water and photosynthates around the plant, enabling them to grow upright and much taller than mosses and their relatives. Although traditionally grouped with other spore-producing plants such as whisk ferns, horsetails and ferns, we now know spikemosses and clubmosses are not closely related to other spore producers.

Spikemosses and clubmosses are often referred to as 'living fossils', as they look very similar to their fossil relatives that lived 370-400 million years ago. However, present-day species differ dramatically in size from fossil species. Present-day 'living fossils' are usually less than one metre tall, whereas their ancestors reached forty metres or more in height. These giants are now extinct; only the smaller sorts survive.

Selaginella is found in most parts of the world and can tolerate a wide range of climates, from the tropics and subtropics, where most are found, to temperate regions and a minority in the Arctic. Most species need moist soils in humid, shaded forest habitats. However, there are few dryland species, such as Selaginella lepidophylla, a native of the deserts of Chihuahua, Mexico. This particular species, also known as the resurrection plant due to its ability seemingly to come back to life from the dead, can withstand years without water. However, following rain it will sprout new green leaves. Spanish missionaries apparently noted this property when they arrived in the New World, using it to illustrate the concept of rebirth to potential converts.

Spikemosses are grown in cultivation for their foliage which comes in various shades of green, with some cultivars being golden or variegated. Selaginella willdenowii is a species with iridescent blue foliage. The colouring is a consequence of elaborate structures on the upper surface of the leaves. Species with underground runners make good ground cover, but they can become invasive under appropriate conditions. For example, in New Zealand the common greenhouse species, Selaginella kraussiana is prohibited from sale and commercial propagation because it is considered invasive.

Further reading

H├ębant C et al. 1984. Ultrastructural basis and developmental control of blue iridescence in Selaginella leaves. American Journal of Botany 71: 216-219.

Huxley A 1999. The New Royal Horticultural Society dictionary of gardening. Groves Dictionaries Inc.

Scott K and Willis K 2016. Botanicum. RBG Kew.

Lucinda Lachelin