Plant
of the Month
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May 2004
Ranunculus
lyallii
Mount Cook Buttercup
by Dr. Mary
Toomey
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Ranunculus lyallii
growing in Mary Toomey's garden
© Mr. Bill O'Sullivan
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Ranunculus lyalli, the largest buttercup in
the world, erroneously known as Mount Cook lily, is
a perennial herb native to New Zealand. It grows wild
in subalpine to low-alpine zones in South Island mountains
from 700 m to 1500 m altitude, chiefly along stream
banks and in wet sites in scrub and grassland. It is
found in the high rainfall areas along the South Island
Main Divide from the Paparoa Range south and reaches
Mt Anglem on Stewart Island. The plant was first discovered
by Dr David Lyall, the surgeon on HMS Acheron, the vessel
employed to survey the southern New Zealand coast from
1847 to 1851. Dr Lyall's collections consisted mainly
of leaves - hence positive identification of the plant
was not possible. A decade or more later, Sir Julis
von Haast and Dr Andrew Sinclair who had collected flowering
specimens identified it as a Ranunculus.
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The glossy green circular
leaves of Ranunculus lyallii
© Mr. Bill O'Sullivan
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Its beautiful pure white flowers and glossy green circular
leaves make it a valuable garden plant. Although the
botanist, Leonard Cockayne in his book, The Cultivation
of New Zealand Plants (1923) stated that Ranunculus
lyalli was difficult to grow, there are records
of its cultivation as early as 1880. There are also
reports that cultivated specimens of Ranunculus lyalli
had naturalised in Dunedin Botanic Garden. Furthermore,
the Bennett family of Broadacres Nurseries near Dunedin
propagated plants for sale in the 1930s. During my visit
to New Zealand a few years ago, the well known horticulturist,
Joe Cartman of Clematis × cartmanii
'Joe' fame, enthused about Ranunculus lyalli.
He informed me about the importance of copious amounts
of water, good drainage and shade in areas with hot
summers for successful cultivation of Ranunculus
lyalli.
Having failed to propagate plants of Mount Cook buttercup
from a packet of seeds I bought in New Zealand, I did
not give up on my wish to grow this buttercup. The plant
growing in my garden came from Blackthorn Nursery in
Hampshire, UK. I planted it very carefully incorporating
sharp sand, plenty of washed lime-free horticultural
grit and peat (to adjust the pH to 5-6) into the planting
hole. Taking into account the plant in its native habitat
grows in infertile wet sites and is intolerant of high
nutrients, I do not mulch or feed my plant excessively
but water it regularly from early spring and throughout
the growing season. The plant has been growing healthily
and vigorously over the past eighteen months and is
in flower right now (mid-May). In New Zealand, the garden
plants flower between November and January although
in the wild they are known to produce scapes (leafless
flower stems) as early as October and as late as May.
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Ranunculus lyallii
© Mr. Bill O'Sullivan
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Description
Ranunculus lyalli grows from a robust, branching
rhizome (swollen underground stem) furnished with a
number of fleshy roots about 40 cm long. The shiny deep
green, large circular leaves are held on strong petioles
(stalks), which are attached to the centre of the leaf
blade. The scapes arising directly from the soil are
long, (30 to 50 cm), stout, fleshy and branched. Each
scape carries anything up to 5 or more flowers, each
measuring 4 - 6 cm wide, with 5 - 6 light green sepals
and 10-20 overlapping white petals and a handsome central
boss of butter-yellow stamens encircling prominent and
firm greenish stigmas. The terminal flowers are larger
than the lateral ones.
Although plants in the wild produce fruits about 2-3
cm long, and made up of numerous very small hairy achenes
(single seeded dry fruitlets) taking about ten to twelve
weeks to ripen after flowering, the plant in my garden
did not bear any fruits last year. I await with interest
to see whether the flowers will set fruit this year.
Ranunculus lyalii is a superb garden worthy
plant, which needs space to grow and flourish.
Contributor
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Dr Mary Toomey,
a keen gardener, international lecturer,
author and broadcaster trained as a biologist,
botanist, entomologist and soil ecologist.
She has been growing and collecting clematis
- a member of the buttercup family, Ranunculaceae
- passionately for over 30 years. She has
studied cultivation of clematis extensively,
both from a practical and theoretical standpoint.
Until recently Mary was the editor of The
Clematis, the journal of the British
Clematis Society. She was elected an honorary
member of the Society in 2000.
Her publications include An
Illustrated Encyclopedia of Clematis
(Timber Press, Portland, Oregon, USA) and
Clematis
- A Hamlyn Care Manual (Hamlyn,
Octopus Publishing Group, London, UK), which
has been published in both English and German.
Mary also participated as a scientific and
linguistic reviewer in the translation of
a major botanical - taxonomical publication,
Släktet Klematis by Dr Magnus
Johnson of Sweden, an internationally renowned
authority on Clematis. The English edition,
The
Genus Clematis was published in
2001.
Mary's wider interest in garden plants
and members of the buttercup family in particular,
was instrumental in the founding of the
much-needed Ranunculaceae Society.
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Photo Credits
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All photos courtesy of Bill O'Sullivan
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