Last weekend I was out with the Kapiti-Mana branch of Forest and Bird, giving them an introduction to ferns. A few weeks back, I gave a similar walking-talk at Otari-Wilton’s Bush in Wellington. Many people find ferns an appealing group to learn. Aside from their iconic status in New Zealand, good learning resources are available, and there are enough different New Zealand ferns to be a challenge without being overwhelming. Most forested sites in New Zealand will be home to between 20 and 50 species of fern.
Te Papa’s online guide to Common New Zealand ferns.
Te Papa’s online guide to New Zealand tree ferns.
When teaching people how to identify a fern plant, I stress that there are four characteristics to initially look for:
1) does it have reproductive structures? Fern reproductive structures occur on the underside (or margins) of the frond. The shape (e.g., round versus elongate into lines) and position (i.e., on the margin or away from the margin) are important. Related ferns almost always have similar reproductive structures, even if their fronds look completely different.
Different groups of ferns are characterised by their reproductive structures, which can come in many forms. Clockwise from top left: 1) Polystichum; shield ferns. The reproductive structures are aggregated into round patches. Each of the black spheres is a sporangium (plural = sporangia), the capsule that produces the spores (in Polystichum, there are 64 spores in each sporangium). A distinct cluster of sporangia is called a sorus (plural = sori). In many ferns the sori are partially covered by protective tissues, called indusia (singular = indusium). In Polystichum, the indusia are round, giving rise to the common name of shield fern for this group. 2) Cardiomanes; kidney fern. The sori occur on the margins and arise from tubular indusia. 3) Gleichenia; tangle ferns. Two or three sporangia (the yellowish dots) occur on the underside of each frond segment. 4) Hypolepis; pig ferns. The sori are on the margin of the frond and are partially protected by the inrolled margin of the frond. 5) Asplenium; spleenwort ferns. The sori occur in lines away from the margin, and are arranged in a ‘herring bone’ pattern. 6) Pteris. The sori line the margins of the frond. Photos Leon Perrie, montage © Te Papa.
The nature of the reproductive structures can be critical for identifying a fern. If I happen upon a fern I don’t know and it does not have reproductive structures, I do not bother attempting to identify it. If you’re learning ferns, I recommend you do the same.
2) does it have scales or hairs or is it naked (glabrous)?
There are two major groups of tree ferns in New Zealand: Cyathea tree ferns are scaly, whereas Dicksonia tree ferns are hairy. Photos Leon Perrie, © Te Papa.
Close up of the scales of Cyathea (left) and the hairs of Dicksonia (right). Photos Leon Perrie, © Te Papa.
Hairs are only one cell wide, but this can only be checked with a microscope. As a general rule, if you can’t decide whether something on a fern is a scale or a hair, call it a scale if it is obviously wider than your own hairs.
3) how divided is the frond? It might be undivided (= “simple”), or once divided, or twice divided… etc.
Loxogramme dictyopteris, lance fern, has undivided/simple fronds. Asplenium oblongifolium, shining spleenwort, has once divided fronds. Asplenium bulbiferum, hen & chickens ferns, has three-times (or nearly so) divided fronds. Photos Leon Perrie, montage © Te Papa.
4) are the fronds tufted, or do they arise along a creeping rhizome (modified stem)?
Left: Blechnum discolor, crown fern, has tufted fronds. Right: In Arthropteris tenella, the fronds arise at intervals along a creeping rhizome; several creeping rhizomes can be seen as brown lines up the tree trunk. Photos Leon Perrie, montage © Te Papa.
Noting these features will help you identify a fern. These features are what I make sure I record when I am collecting and/or photographing ferns.
The Kapiti-Mana Forest and Bird trip was to Mangaone Walkway near Waikanae. Below are the ferns we discussed. Several of them already feature in:
Te Papa’s online guide to Common New Zealand ferns.
Blechnum novae-zelandiae, kiokio. Most Blechnum species have different looking fertile (top left) and sterile fronds. Fertile Blechnum fronds are usually reduced to narrow segments, which are green when young, black when the spores are mature, and brown after the spores have been shed. Most Blechnum species also have only once-divided fronds. Photo Leon Perrie. © Te Papa.
Blechnum fluviatile, creek fern. Photo Leon Perrie. © Leon Perrie.
Blechnum discolor, crown fern. Photo Leon Perrie. © Te Papa.
Blechnum colensoi, Colenso’s hard fern. Photo Leon Perrie. © Te Papa.
Cyathea smithii, kätote. A scaly tree fern. Has a distinctive skirt of dead frond stalks. Photo Leon Perrie. (c) Leon Perrie.
Dicksonia squarrosa, whekï. A hairy tree fern. Photo Leon Perrie. © Leon Perrie.
Asplenium flaccidum, hanging spleenwort. Usually grows from tree trunks. Photo Leon Perrie. © Leon Perrie.
Asplenium bulbiferum, hen & chickens fern. This looks very different to the hanging spleenwort, but they have the same arrangement of their reproductive structures, reflecting their close relationship. (They commonly form (sterile) hybrids.) Photo Leon Perrie. © Te Papa.
Microsorum pustulatum, hound’s tongue fern. Photo Leon Perrie. © Leon Perrie.
Hymenophyllum revolutum. Filmy ferns have very thin leaves, and many look translucent. There are three principal groups in New Zealand: Hymenophyllum, Trichomanes, and Cardiomanes. Most Hymenophyllum species have their reproductive structures enclosed by two separate flaps. Photo Leon Perrie. © Leon Perrie.
Trichomanes venosum. In Trichomanes, the reproductive structures are enclosed by a tubular, often trumpet-like structure. Photo Leon Perrie. © Te Papa.
Cardiomanes reniforme, kidney fern. More closely related to Hymenophyllum than Trichomanes, although the reproductive structures are at least superficially more similar to the latter. Photo Leon Perrie. © Leon Perrie.
Leptopteris hymenophylloides, single crape fern. The sporangia are spread over the frond underside rather than being clustered into sori of regular shape and size. The frond is translucent like a filmy fern. Photo Leon Perrie. © Te Papa.
Tmesipteris elongata, a fork fern. More closely related to ferns than to seed plants or lycophytes. Nevertheless, the relationship is a distant one, and it doesn’t look very fern like. There are at least five species in New Zealand, and they are usually epiphytic on tree ferns. Photo Leon Perrie. © Te Papa.
Lycopodium volubile. A lycophyte rather than a fern. Ferns are more closely related to seed plants than they are to lycophytes, but ferns and lycophytes share a similar mode of reproduction. The leaves of lycophytes are only small, and the leaves bearing sporangia are often clustered into distinct ‘cones’, which are the pendulous, brown structures in this image. Photo Leon Perrie. © Leon Perrie.