Tmesipteris growing on Dicksonia in an English garden

Tmesipteris or Fork Ferns are a small genus of primitive ferns related to the Whisk Ferns, Psilotum. They originate from Australia and islands in the South-west Pacific. Occasionally found on imported trunks of tree ferns, usually Dicksonia antarctica they are rarely seen now as trunks are vigorously cleansed of all epiphytes. I have occasionally noticed Tmesipteris on trunks of tree ferns grown undercover and once on a Dicksonia in a Cornish garden. I have also been notified of plants in an Irish garden but usually they do not seem to persist for long. Therefore it was of some interest that Colin Pope, a volunteer at Ventnor Botanic Garden, Isle of Wight, reported finding several plants growing on Dicksonia in the gardens. Earlier this week Andrew Leonard and I met with Colin on the Isle of Wight and he showed us the colony. The Dicksonias were planted in 2005 in a small gulley. Some were imported from Tasmania and supplemented with smaller plants obtained from Logan Botanic Garden. The Tmesipteris were seen on 4 trunks of the Tasmanian specimens and around 30 ‘fronds’ were present. It is difficult to work out if some of these ‘fronds’ were separate plants or if some were arising from a hidden rhizome. Most of the fronds seemed healthy and the colony seems to be thriving. Colin said that some of the smaller ‘fronds’ appear to be recent so the colony may be increasing in size. 2 fronds bore ‘sporangia’, correctly termed synangia, and I was able to identify them as probable T. obliqua which is endemic to South-east Australia. Microsorum pustulatum and Rumohra adiantiformis were also present on some of the Dicksonias. It is of great interest that this colony has been noticed and can be monitored for signs of decline or increase in the future.

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3 thoughts on “Tmesipteris growing on Dicksonia in an English garden”

  1. Have other fern genera been found on Dicksonia or Cyathea imported from Australasia? One unsubstantiated theory about the arrival of the Australasian micro-moth Musotima nitidalis (pictured) in the UK, first recorded in 2009, is that it ‘hitch-hiked’ on a tree fern even though these are not the larval food plants. But did it come via an epiphyte and are there records of e..g. epiphytic Adiantum or Asplenium in Australia or New Zealand, or indeed in the UK?

  2. Yes is the simple answer. There are a fair number of ferns and allied plants and an even greater number of bryophytes which have obviously hitch-hiked. I published on this in the Fern Gazette back in 1993 when recording Polyphlebium venosum in a Cornish garden. In my own garden a small Dicksonia produced a Microsorum but only a year or so after it had been growing here – the propagules/rhizome fragments must have been deep between the leaf bases and resisted the “cleaning” which things are now subjected to. This route has also been suggested to be how the New Zealand flatworms entered this country.

  3. A belated thanks for your reply. Recent work on the moth suggests UK individuals are closer to Australian than NZ populations, not that this gets us any closer to elucidating the mode of import.

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