Identifying maidenhair spleenwort ferns.

The maidenhair spleenwort is a spleenwort fern (Asplenium) that (supposedly) looks like a maidenhair fern (Adiantum, see below). The 600 or so of the world’s spleenworts are characterised by having their reproductive structures in lines away from the margins of their fronds’ undersides.

asplenium_trichomanes_sori_edit

The reproductive structures (the sori, made up of the sporangia which contain the spores, and their protective indusia) of maidenhair spleenwort, on the underside of a frond.

Two maidenhair spleenworts occur in New Zealand. They look very similar, but one has four sets of chromosomes (tetraploid) and the other six (hexaploid). This difference in chromosome number means they cannot interbreed. In New Zealand, the hexaploid is common, but the tetraploid is rare, only being known from the Hawke’s Bay, and only recently being rediscovered. Outside New Zealand, the hexaploid is rare, being known from only a few places in Australia, while the tetraploid is common and widespread around the world.

Tetraploid and hexaploid plants of maidenhair spleenwort.

Tetraploid and hexaploid plants of maidenhair spleenwort.

distributionmaps

The distributions of the maidenhair spleenworts in New Zealand.

  

Maidenhair spleenworts are most commonly found on limestone rock. They can be out in the open, or under semi-shade, but usually in fairly dry conditions. They often hold their fronds erect, whereas other ferns growing from rock usually have pendulous fronds.

Open, limestone outcrops; a habitat for maidenhair spleenworts.

Open, limestone outcrops; a habitat for maidenhair spleenworts.

The taxonomy of New Zealand’s maidenhair spleenworts is still being researched. The tetraploid may be referable to Asplenium trichomanes subsp. quadrivalens. The correct scientific name for the hexaploid, the most common maidenhair spleenwort in New Zealand, is presently unclear.

Maidenhair spleenworts can be distinguished from other New Zealand ferns by the combination of their typical spleenwort reproductive structures (see above), and their frond stems which are almost black, almost smooth (without hairs and with only a few scales), and undivided (i.e., the stems do not branch). Similar-looking  ferns in New Zealand are described below.

 
Necklace fern, Asplenium flabellifolium.
A spleenwort or Asplenium fern like the maidenhair spleenworts can be most obviously distinguished from the maidenhair spleenworts by its green stem.

 

asplenium_flabellifolium1

Necklace fern, Asplenium flabellifolium.

Maidenhairs, Adiantum.
The maidenhairs are most obviously distinguished from the maidenhair spleenworts by the branching stems of their fronds. The Small maidenhair (Adiantum diaphanum) can sometimes have unbranched frond stems, but it, like all maidenhairs, can be reliably distinguished by having the reproductive structures on the margins of their fronds’ undersides.

A maidenhair fern, Adiantum fulvum.

A maidenhair fern, Adiantum fulvum.

Button fern, Pellaea rotundifolia.
The brown and scaly frond stems and reproductive structures on the margins of their fronds’ undersides distinguish button ferns from the maidenhair spleenworts.

The Button fern, Pellaea rotundifolia.

The Button fern, Pellaea rotundifolia.

Blechnum ferns.
Like most Blechnum ferns, Creek fern (Blechnum fluviatile) and Lance fern (Blechnum chambersii) have very different looking fertile and sterile fronds. Those fronds that are making spores have much narrower segments, are held more erect, and are black or brown (they are not dead despite their lack of greenness!).

blechnum_fluviatile_chambersii

Blechnum chambersii or Lance fern (left) and Blechnum fluviatile or Creek fern (right). The blue arrows indicate fertile fronds.

 

We are still interested in learning more about the maidenhair spleenworts in the southern North Island (south of, and not including, the Waikato). I would be very grateful for notification (and a photo) if you think you have found maidenhair spleenwort in the southern North Island. Please either email (leonp@tepapa.govt.nz), phone (04 381 7261), or write me (Leon Perrie, Te Papa, PO Box 467, Wellington).

4 Responses

  1. Leon Perrie

    Hi Joseph,
    Southern.
    But it could well be any where in Hawke’s Bay, where there is limestone.
    Leon

    Reply
  2. Joseph

    what part of Hawke’s bay was this plant rediscovered am doing a bit of research if anyone could help flip me a txt on 0272220234

    Reply
  3. Annette Thomas

    25.2.09
    Thank you for your email regarding the Maidenhair Spleenwort Ferns. Very interesting but still not sure about ours so have sent you a leaf to see what you think.
    Regard
    Annette Thomas

    Reply
  4. Bruce Clarke

    Thank you for your email with the link to this site.
    Very interesting and informative.

    Regards
    Bruce Clarke

    Reply

Leave a Reply

  • (will not be published)