Undoubtedly,
one of the highlights of my time at Kew so far has been maintaining and
becoming acquainted with the large Passiflora collection held in Zone 9!
Passiflora is a genus containing over 500 species that are mostly found in
tropical South America, and to a lesser extent in places such as North America,
Southeast Asia and Australia. The simplest way I can describe them is as the
tropical version of Clematis; vigorous blighters that clamber about all over
the shop on tendrils, and with delightfully beautiful flowers that are
consistently showy and fascinating across the genus! These amazing flowers have
been captivating horticulturally-disposed eggs for centuries, as far back as
the 16th century they were being lauded and praised for their
beauty. Spanish Jesuit priests were convinced that these flowers symbolised the
Passion of Jesus Christ, and attributed the complex flower parts to the various
elements involved in the crucifixion. The Latin word passio means suffering, and this religious association continued in
the naming of the genus by Linnaeus.
The
stereotypical Passiflora bloom is large and showy, with a crown around the
flower known as the corona that acts as an attractor and landing pad for pollinators
such as bumblebees. An inner corona leads to the nectar, which the bees extract
in the traditional manner with their tongues! This corona is stunted in species
pollinated by hummingbirds (landing pad not required), but the floral tube
leading to the nectaries is much longer, about 10cm, to account for the long
beak of these graceful birds. The arrangement of the male and female flower
parts is quite unique, with the male anthers pointing down towards the flower.
Pollen transfers from these on to the backs or heads of bees and birds
respectively, as they brush against the anthers before consequently brushing against
other flowers when they cheerfully continue on their pollination rounds. The
female parts are also conspicuously arranged, generally seen in threes and
always standing upright as the flower opens. A period of time elapses after
opening, this quirk dependent on the particular species, after which the stigma
then also begins to slowly point down towards the flower. This brings it
slightly closer to the action where the pollinators are drinking nectar, and
enables it to better receive pollen from the slurping bees and birds. The aim
of this remarkable skulduggery is to limit the chance of self-pollination, by leaving
a window of time in which the pollen on the anthers can be removed by the
first eager visitor. Appearing
after this raises the possibility of coming into contact with pollen from
another flower, which increases genetic variation and creates stronger plants
in the next generation!
In
terms of cultivation, one of the most enticing aspects of Passiflora is their
ability to flower well as container grown plants. The majority of the specimens
in Zone 9 are growing in 5L pots and are regularly hacked back throughout the
year to keep their vigorous growth in check, but in spite of this apparently
rough treatment a large majority of the species flower well, and even at this
time of year with the ever-reducing light levels. For growers in England,
containers and a greenhouse are generally required to get near these
predominantly tropical plants. There is happiness in the world however, as near-hardy
specimens are available to enthusiasts in our less balmy climes, with Passiflora
caerulea the hardiest for cultivation in England. This species will endure
temperatures below freezing when planted in a sheltered spot and offered some protection;
with good drainage the key to limping it through our cold and damp winters (wet
cold quickly croaks the roots). Fortunately P. caerulea hybridises readily, and
the hardiest hybrids available are those involving this species in the parentage.
P. ‘Amethyst’ and P. ‘Clear Sky’ are two notable examples, but there have been
over a hundred created (where there is a will, there is a way!) An unheated yet
frost-free greenhouse or windowsill would obviously be an ideal situation to
overwinter a container grown P. caerulea hybrid, brought in from the garden
after a prune that results in at least some green leaves being left on the plant,
and tied-in to four foot or so of canes to support any winter growth.
I am smitten, as this
rambling on indicates! Enough jabbering, here is some Passiflora glory!
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| Passiflora
umbilicata, a glorious specimen from Argentina and Bolivia. Pollinated by
hummingbirds, it is unique amongst Passiflora as all other species pollinated
in this way are either red or pink |
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| The
ripening fruit of Passiflora foetida. The Latin epithet ‘foetida’ normally
relates to something foul smelling, in this case the flowers smell sweetly but
the hairs on the leaves pong when disturbed |
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| Another
of the hardier hybrids, P. x violaceae, British-born in 1819 and the first
hybrid ever created by crossing P. racemosa and P. caerulea. Flowering in Zone
9 for the past three months! |
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| Many
red-flowering species are difficult to maintain, but Passiflora ‘Lady Margaret’
is amongst the hardiest and flowers freely |
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| Passiflora
siamica, a rare gem from China. Last week a Passiflora expert spent almost
thirty minutes in Zone 9 photographing these blooms, and actually picked three ‘to
take home and dissect’! This eccentric mayhem is explained by the uniquely large number
of male and female flowering parts |
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| One
of the most wonderful hybrids housed in Zone 9, Passiflora x belottii, born from
a cross between P. alata and P. caerulea. Sweet smelling, very free-flowering,
and the contrasting pink petals and white sepals are a thing of beauty! |
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| Passiflora
organensis with the anthers
pointing downwards and loaded with pollen, ready to brush
on to the head of the pollinator as they reach in to claim their nectar reward |
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| Several
of the smaller flowered species have a rich, deep purple to the undersides of
the leaves. This is Passiflora vespertilio, widespread in South America and not
tolerant of cool temperatures. Latin for bat is vesper, while vespertilius
means ‘resembling a bat’; in this case relating to the outline of the foliage |
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| Another
dalzzling hybrid, Passiflora ‘Red Infinity’ |
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| Passiflora
herbertiana is one of three species found in Australia. Aborigines eat the
fruits! This chap is a real bloodhound; self-fertile, relentlessly
free-flowering (sprung straight back into bloom after a recent chopping back),
and very tolerant of cooler temperatures. Worth a look! |
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| The
forming fruit on a recently pollinated flower. After many failed attempts at
crossing species this fruit has finally set for me! A long process ahead of
seed ripening, germination and seedling growth, but Carlos is optimistic about
the parents I chose and the potential hybrids |
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| Another
of the slightly hardier species, Passiflora amethystina, that flowers extremely
well when grown in a pot with blooms up to 10cm across! |
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The
foliage of Passiflora species is the most varied of any genus, often displaying
dramatic lobes such as here with P. obtusifolia. This variation creates a
disguise, in an attempt to bamboozle Heliconius butterflies. These beautiful
creatures lay their eggs on Passiflora leaves, and the following caterpillars
feed ravenously! Other defences used include hairy leaves that trap
caterpillars, foliage with toxins, and nectar glands on the leaves which
attract ants and wasps that will naturally predate caterpillars
|
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| Dryas
iulia, the Julia Heliconian, native to Southern and Northern America and seen
here at Stratford Butterfly Farm |
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| Heliconius
ismenius, the Tiger Heliconian, native to similar regions and again seen at
Stratford Butterfly Farm |
