THE TREE FERNS OF THE KLAASSENBOSCH
GREEN BELT
Since 18
months ago we have seen many small tree ferns appearing in the moist areas at
the top of the arboretum. I knew these would not be Cyathey capensis which is indigenous on the Peninsula, because they
produce almost no offspring here in the west. As a second prize I had hoped
that these would be Cyathea dregei
(indigenous to the Cape South Coast and up to tropical Africa).The previous
owner of a property adjacent to the green belt had planted 9 of this species in
the garden and they have produced spores now for 50 years, but without
offspring. Unfortunately the new juveniles in Klaassenbosch are probably Cyathea cooperi, an invader from
Australia. This tree fern creates problems in many parts of the world. Some
information is supplied below which can help identify specimens.
This is part of a leaf of Cyathea dregei. The number of sori varies
between about 3 to 7. The trunks can reach 500 mm after 50 years, and the
height of the crown some 5 m.
This is part of a leaf of Cyathea cooperi. The sori are in pairs
of two, but there are typically 8 pairs, which makes it easy to distinguish
from dregei.
The trunks are
thinner than dregei, closer to 250 mm
diameter after many years. Cooperi
has spread to various parts of the Cecilia forest and (possibly Newlands?).
The locally
indigenous species is Cyathea capensis.
They grow in the Cecilia forest, near the waterfall. It is seen that the sori form a zig-zag
pattern, unlike dregei and cooperi. Capensis grows at higher altitudes (e.g. more than 800 m) and may
not thrive at the Klaassenbosch altitude of about 100 m.
Capensis can be bought at one nursery for R
550 each, but it does not help to plant
a scarce species if the conditions are not ideal.
A very interesting feature of capensis is the presence of a strange
woolly growth in its crown, called aphlebia.
This is a prehistoric feature and Wikipedia puts the matter in context. In the
glass house in Kirstenbosch such a plant can be seen, near the stones with
fossils.
Further down the stream (at GPS S 34 55.555 and E 26 666.666) in Klaasenbosch a few
adult Cyathea’s are growing. Two are dregei, planted by the previous owner of
an adjacent property.
The other
one has a trunk of some 400 mm in diameter, but to my surprise the leaves had
more than 4 pairs of sori, which ruled out dregei.
I am not willing to take a guess which of the other few hundred Cyathea species it might be. We need an
expert here to identify the species on the left.
Often nurseries sell tree ferns
without identifying the species. One may easily buy an invader without
realising it. This is probably a Cyathea,
but the pattern is not a typical cooperi.
I had
thought for a long time that there are Dicksonia tree ferns along the stream.
They have slender trunks and the sori are not spaced close together, as shown
on the left.
Dicksonia
antartica is a popular tree fern sold by nurseries worldwide.
I have tried
to find any specimens in the green belt (escaped from neighbouring gardens),
but fortunately could not find any. Those with the slender trunks all turned
out to be cooperi.
These notes
were not written by a botanist, but for further reading the following excellent
book is recommended:
» Author: Neil Crouch; Ronell Klopper; John Burrows; Sandra
Burrows » Title: Ferns of Southern Africa: A Comprehensive Guide » ISBN:
9781770079106 » Format: Softcover » Release Date: September 2011 » Imprint:
Nature » Pages: 760 » Price: R420.00 - See more at:
http://www.randomstruik.co.za/books/ferns-of-southern-africa-a-comprehensive-guide/4357#sthash.wFvHYQzz.dpuf
Also visit http://www.fernsoc.co.za.
Picture
acknowledgement:
(The photographs were
taken of leaflets in the green belt and the Cecilia forest and were not taken
from copyrighted sources, except for the dicksonia.
An attempt will be made to photograph a leaflet at a nursery.).