Contents
of the Summer 2013 Northants News
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A
Cucurbit Conundrum
Roland Tebbenham
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Some
years ago I purchased a mixed box of fairly tatty plants at an auction of
a sadly neglected collection. I trimmed and propagated the living plants,
but I could not identify one greyish-brown stick with a few ragged
thickened leaves, so I ‘parked’ it. A couple of years later it started
to grow after an accidental spring watering, and shortly afterwards I saw
a photograph on the BCSS Forum of a plant that looked vaguely similar to
my neglected specimen. I did some research and identified it as Xerosicyos
danguyi. I
took a tip cutting from the original battered ‘bin-end’ to obtain a
more vigorous plant. It rooted quickly and the stem extended well, growing
some nice clean new leaves last year, and then in the middle of winter it
produced two clusters of small, strange flowers.
Xerosicyos
is a small genus of shrubby dioecious cucurbits that grow in south &
south-west Madagascar on limestone or gneiss in dry bush and dune
habitats. They are mostly climbers with bifid tendrils, but one (Xerosicyos pubescens)
has an above-ground caudex. Xerosicyos
danguyi has
succulent leaves, a characteristic that is unusual in the cucumber family:
compare the large caudex plants in the genera Corallocarpus, Gerrardanthus,
Ibervillea, Kedrostis
and Momordica.
The flowers are borne
on 10mm pedicels in loose fascicles (bundles) and are generally green or
greenish-yellow. The male flowers are ‘square’ and open with four 3mm
long petals and distinct stamens with pollen. The female flowers have
similar sized petals and pairs of stigmas – as is the case with my
plant. The fruits are, like many succulent cucurbits, brownish-orange
ovoid objects; in this species they are 20mm long and dry. However I have
yet to see any on my plant owing to the absence of a male flowering
coincidently.
This species has a
common name ‘The Silver Dollar Plant’ – quite appropriate since the
leaves are circular and silvery-green in colour. It is sold as a
houseplant and whilst it may not be the most sculptural succulent, it is a
tough addition to any collection. My, admittedly limited, experience
indicates a neutral, well-drained compost works fine and my old plant is
tolerant of 5C when kept dry over winter. However I kept the cutting above
12C and watered it all year in a propagator and it flowered; so you take
your choice. I read that it flowers in the summer like other caudiciform
cucurbits.
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If
you appreciate the beauty of green flowers contrasted with silvery
foliage/bodies like the cactus Echinocereus
viridiflorus
or the terrestrial orchid Cymbidium lowianum
this is a plant for you! Also if any member has a male Xerosicyos
danguyi please
get in touch as I would like to try to pollinate mine.
Roland
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References:
[1] ‘Illustrated
Handbook of Succulent Plants’ ed. U Eggli [Springer 2002]
[2] ‘Succulent
& Xerophytic Plants of Madagascar’ W Rauh [Strawberry Press 1998]
[3] ‘Succulent
Cucurbits’ Leo A Martin [Central Arizona C&S Soc]
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Rock
Garden Delosperma
Trevor Wray
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I have recently replanted a rock garden and made
the tour of my favourite nurseries for new plants. These days, beside the usual
Sedum and Sempervivum, several new kinds of succulents are available from alpine
specialists. I bought Rosularia
sempervivum and a
couple of Delosperma,
D. congesta ‘Gold
Nugget’ and D. ‘Ruby Coral’.
On their online encyclopaedia the
Alpine Garden Society say of Delosperma...
“In
general the genus is too tender and sensitive to excess moisture to be of value
of the rock gardener. However, a few will stand light frost and can either be
grown on the rock garden, raised bed, dry wall or alpine house.”
So
probably not a long term prospect. Delosperma
nubigena. sometime
called ‘sp. Basutoland’. comes from 3200m, (guess where?), and has been
around for some time. I tried it once outside and bits survived the first winter
but not the next. In a cold frame covered for the worst of the winter it has run
amok so probably just as well it is not too hardy outside. Whether these new
species will survive will be tested. Naturally I will take a few cuttings as
hostage to fortune. All the Delosperma I grow have been fine in a cold
greenhouse. Delosperma
sphalmanthoides is a
little beauty.
While I was looking on the AGS site
I tried Rosularia and read,
They
“are
mainly frost-hardy but dislike winter wet, so need alpine house conditions, or
an overhung crevice or dry wall in the lee of rainbearing winds.”
Maybe another one to take an offset
from before winter. I have tried to give these plants a chance; they are planted
in full sun on several inches of rock chips: so excellent drainage. It would be
nice if these plants could be accommodated outside because they look so much in
keeping with the more classic alpines. Perhaps with global warming coming…
Trev
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Left:
Delosperma
congesta ‘Gold
Nugget’
Right:
Delosperma
‘Ruby Coral’. This seems to be fairly new to general cultivation with
internet information from Holland and Germany. It is not clear what the
species is though one site says alpinum and this seems feasible.
These
plants open their flowers at lunchtime on sunny days. The plants have just
been planted out and are more or less as bought.
So
let’s see what happens in winter. |
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