Cycads - The Plants & Their Cultivation
An introduction to these interesting and ancient
plants.
Andrew Shaw, 15 Ancona Rise, Darfield, Barnsley, South Yorkshire,
U.K.
Chamaerops No. 6, published online 23-10-2002
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Cycas revoluta: just say go.
The living cycads are a group of primitive tropical
and subtropical plants which have changed very little over millions
of years. During the Jurassic period (160 million years ago), cycads
formed the forests of the world. This has led the species surviving
today to become affectionately known as 'living fossils', despite
the evidence pointing to them actually evolving comparatively recently.
Their closest living relatives are Gingko, the Maidenhair Fern Tree,
Gnetum and the curious Welwitschia from the harsh Namib Desert.
Today, botanists recognise four families of cycads
in the order Cycadales. The first of these families, the Cycadaceae,
contains only those species of the genus Cycas. The Zamiaceae encompass
eight genera and represent the largest number of families, namely,
Zamia, Ceratozamia, Chigua (described only in 1989), Microcycas,
Dioon, Encephalartos, Macrozamia and Lepidozamia. A line of thinking,
however, is that Dioon should be 'split off' into a group of its
own. The third family, Boweniaceae, comprises only the genus Bowenia
from Australia whilst the only member of the last family, Stangeriaceae
is Stangeria eriopus from South Africa. In total, these genera contain
around 180 species, many of which are classed as rare, vulnerable
or are even threatened with extinction in the wild.
Cycads are altogether very attractive plants - many
resembling palms in appearance with pinnate leaves and scaly trunks.
Thus, they are in heavy demand for landscaping in the warmer parts
of the world. In cooler climes however, they make excellent pot
plants, certainly a change from the humble Rubber Plant!
Although I am certainly not the last word in cycad
cultivation, I would like to describe the way that I grow them,
and also the observations I have made, which will hopefully help
other growers.
The only real method of propagating cycads available
to the amateur, is from seed. In some families, seed will develop
regardless of pollination taking place or not. This especially applies
to Encephalartos and can cause problems since only seed resulting
from pollination will germinate. Apart from cutting seeds open to
determine the presence or absence of an embryo (difficult and rendering
the seed useless in the process) there is no reliable test for seed
viability. The so-called 'water test', where seeds which float when
placed in water are deemed unviable, in my opinion, does not work.
Several seeds, which I have germinated, floated prior to sowing
and indeed some species of cycads actually have seeds designed to
float to aid distribution. I tend to assume all seeds to be viable
and sow the lot; they're much too valuable to simply throw away
without sowing!
The seed itself may arrive from suppliers cleaned
or with its fleshy seed coat still intact. If the latter is the
case, I soak the seed and then remove the fleshy 'fruit' with a
sharp knife. I do this for two reasons: firstly, the seed coat may
contain germination inhibitors and secondly, its high sugar content
will almost certainly induce fungal contamination. Cleaned seed
I have found to be remarkably resistant to fungus.
The cleaned seed is then either scarified (part
of the hard seed thinned down) and soaked for 24 hours in tepid
water or simply soaked for 48 hours. Both methods seem to yield
similar germination results, at least from my trials so far, albeit
with small amounts of seed.
After soaking, the next treatment is with an antifungal
agent. I have found yellow sulphur to be more effective than proprietary
fungicides such as Benlate. All I do is simply dry the seeds with
a cloth and then roll them in the sulphur.
Next the sowing. The compost mixture I use consists
of four parts peat, two parts of vermiculite and one part of grit
sand.
Once mixed thoroughly it is made only SLIGHTLY damp.
A handful or so is then placed into a polythene bag and the seed
placed on top of this compost, but not fully buried, before the
bag is sealed. I find this method better than using a pot of compost
since it allows the seeds to be checked for germination more easily.
My preferred temperature for germination is around
28°C in an electric propagator, but an airing cupboard works
equally well providing it does not get too hot. I have also germinated
seeds at temperatures down to 17°C. Cycad seeds actually begin
to develop soon after being shed from the parent plant and so may
not germinate for several months after this time.
Seed from commercial sources, if viable, has usually
been stored for some time and so may germinate fairly quickly after
sowing. The shortest time in which seeds of mine have germinated
is 4 days, these being Cycas cairnsiana and Macrozamia lucida. I
generally remove germinated seeds from the bags just as the first
frond starts to show. They are then potted up into a similar mixture
to that used for germination but with extra coarse perlite or grit
added to improve drainage.
As the first frond emerges, I turn the pot so that
the frond points in the direction of the incidental light. After
this time, the pot is NOT moved to prevent the developing frond
from distorting. Even with older plants I do not move them whilst
they are producing new leaves.
As for watering, I allow my plants to become quite
dry before giving them a good watering. They will tolerate drought
better than over watering!
Feeding takes place about every ten days with a
liquid feed.
It may seem from all this that cycads are difficult,
but if good seed is obtained, they are in fact very easy and rewarding
plants to grow.
If possible, I would like to correspond with other
cycad enthusiasts to discuss cultivation techniques and sources
of seeds and I hope to see the observations of others printed in
Chamaerops. Happy growing!
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