Ferns

Ferns and Fern Allies

UBC Botanical Garden has a diverse collection of more than 100 different ferns and fern allies. These are represented by 34 separate genera in 14 families. The majority of these are species or variants of species as they occur in the wild—many propagated in our own nursery from spores collected in the wild—and more than 30 species in the collection are British Columbia natives. The diversity of the fern collection is recognized in our affiliate garden status with the Hardy Fern Foundation.

Ferns and fern relatives are known as Pteridophytes. Unlike seed plants, ferns and their allies reproduce by spores. A spore is a specialized cell capable of developing into a new individual, either on its own or after fusion with another spore. The different groups of Pteridophytes are generally recognized on the basis of gross morphology (overall shape and physical features) as well as by the pattern of sporangia (spore-producing structures) that appear. The typical true fern produces sporangia in discrete clusters known as sori (singular sorus) on the undersides of the fronds (leaves). Fern allies, which includes the horsetails, quillworts, water clovers, club-mosses and spike-mosses, among others, have various, often cryptic (not easily seen) features that distinguish them. However, many have sporangia arranged in cone-like structures. The most prominent and familiar of the fern allies include the genus Equisetum, the horsetails, and the genus Lycopodium, the club mosses.

In ferns, the spore germinates and grows into a tiny leafy structure called a prothallus. Sperm and egg cells are produced on the prothallus and when they unite, the true fern structure begins to grow. While spores are somewhat resistant structures, sperm and egg cells are delicate and extremely short-lived. Both spore germination and movement of the swimming sperm to the egg on the prothallus can only take place in a film of water. This requirement generally restricts ferns to moist habitats, but a large number of fern species are also adapted to drier conditions. The apparent paradox is explained by rapid growth and spore dispersal coinciding precisely with the limited rainy season. Desert dwelling ferns also have small fronds that die back to a drought resistant crown when moisture is restricted.

The Garden has a range of both deciduous and evergreen ferns. Our largest evergreens are the chain ferns (genus Woodwardia), so named because the arrangement of sporangial cases on the back side of the fronds suggests links in a chain. Woodwardia fimbriata (giant chain fern) grows vase-like with leaves that can reach 1.7 m long. It is native to California and sparingly to the Pacific coast as far north as Texada Island. The equally interesting W. prolifera (Formosan chain fern) is one of about fifteen species native to China. The Formosan chain fern has leaves that grow to 2 m long and that are viviparous, producing vegetative buds on the upper surface of the fronds, which produce roots and form new plants when they contact the ground.

At the other end of the scale, our smallest is the tiny maidenhair spleenwort, Asplenium trichomanes, which has delicate, pinnate fronds. Normally epipetric (growing on rocks), A. trichomanes is native to both North America and Europe. The alpine water fern, Blechnum penna-marina is another tiny evergreen. It is a pretty, ground-hugging fern, native to southern South America, parts of Australia and some of the Pacific Islands. Like other Blechnum species, B. penna-marina has dimorphic fronds, the fertile, spore-bearing fronds deciduous and borne separately.