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eported that, with the notable exception of Cyathea contaminans, few tree-ferns occupy
major disturbance sites.
Alastair Wardlaw and Martin Rickard chaired a discussion on the conservation of treeferns.
Clive Jermy, unavoidably absent, had prepared a useful handout with some key points
for consideration.
Much discussion took place on whether the bureaucracy surrounding CITES (Convention
on International Trade in Endangered Species) and other legislation designed to protect
either the ferns themselves or the rights of the country of origin was in fact hampering the
process of conservation. It is difficult to obtain material of different species of tree-ferns for
ex situ conservation. Chris Page spoke about one Darwin Initiative Project that had helped
in the conservation of the ferns of Mauritius. Flora & Fauna International’s indigenous
propagation projects were also mentioned; these aim to provide a viable replacement for
trade in indigenous plants.
Barry Thomas then gave us an illustrated talk on the fascinating subject of ‘Fossil treeferns’.
He showed us how the earliest land plants such as Cooksonia evolved within a short
space of time to give larger descendants of which some started to grow upwards to exploit
the advantages that size gave. The problems of recognising tree-ferns in the fossil record
were outlined and the advantages of finding anatomically preserved stems stressed. The
range of fossil remains of tree-ferns was reviewed from the Palaeozoic to the present day,
including much new work published in the last few years. Two types of stem anatomy are
known to have evolved several times in different families of ferns. The commoner type
increases in size by dividing its vascular strand as is found in the Marrattialeans (known
from the Carboniferous onwards), the Osmundaceae (that were largest in the Permian), the
Cyatheaceae and the Dicksoniaceae. The other stem type (such as in some new
Carboniferous petrified stems and in the Mesozoic Tempskya, although none are known
today) was actually a series of interwoven stems and, like the other type, covered in a dense,
supporting root mantle. Although rather different, both forms were strong and flexible.
Visually, though, the two stem types were rather different. The commoner tree-ferns, that
we all know, have a crown of fronds, but the others grew leaves along the lengths of their
interwoven stems. We clearly do not know enough about tree-fern evolution yet, but Barry
was optimistic that new discoveries would continue to increase our knowledge of it.
In his talk ‘Tree-ferns growing outside in Britain’, Alastair Wardlaw reported that tree-ferns
have been grown in Britain since at least 1786. Only one, however, according to the The New
Atlas of the British and Irish Flora (2002) has become established in the wild, and that is
Dicksonia antarctica. Although the limit of latitude in which tree-ferns grow in the southern
hemisphere is equivalent to the middle of France, in gardening we do not have the same
constraints since we are not hostage to the prothallus stage and can even ‘avoid’ the early years
of the sporeling’s growth. As early as 1872, Arthur Smee was describing his cultivation in both
pots and in open ground in London and this was at the time immediately before the Thames
froze over in many winters. Alastair went on to describe a number of experiments that he had
carried out to protect his plants in the Glasgow region. He had also measured the temperature
inside and outside his various coverings as well as in the crowns of the plants and interpreted
these temperatures in the light of any damage to the plants the following year.
A general discussion then ensued on the day’s proceedings, when mention was made about the
nature of hardiness of the southern-most colonies of the commonly grown tree-ferns and why
it may not be possible to replicate these conditions in a typical northern hemisphere garden.
Our hosts for the day thanked our distinguished guests and were in turn thanked for
organising such an informative and interesting day. About 65 people were counted at one
point of the day, which is quite a large fraction of the inland membership.
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