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Saturday, April 30, 2011

Bird of Paradise flower, Strelitzia reginae,Strelitziaceae

I've waited a long time for this. I bought this Strelitzia reginae as a small plant several years ago and made the fundamental mistake of planting it in a large pot, so it's been producing leaves rather than flowers until now. Back in November a flower bud appeared but its growth slowed right down in our unheated conservatory, but April's warmth has brought it into flower

There's no doubt that the Strelitzia bloom is very bird-like. It's also pollinated by birds - sunbirds - in its native South Africa
Hummingbirds in the New World hover in front of flowers and so burn up a lot of energy as they refuel with nectar, but sunbirds have a far more relaxed strategy, using the blue stamen of the flower as a perch

The stamen is a complex structure, formed by two elongated, fused blue petals and tipped with the white pointed stigma. The third blue petal that you can see here at its base is much smaller and conceals the nectar.

When the bird lands on the stamen its weight pushes it downwards, splitting the fused petals longitudinally and exposing the white pollen, which sticks to the bird's feet

When it visits another flower it lands on its stamen and while it's shuffling around probing for nectar it transfers pollen to the pointed white stigmatic surface that you can see above

A new flower rises from the inflorescence spathe every day. This is day two and I'm expecting three more

This is a flower deemed fit for a queen and was named by Sir Joseph Banks in honour of Charlotte of Mecklenburg-Strelitz (1744-1818), King George the Third's Queen-Consort, who was an avid botanist and great patron of Kew Gardens.

Wednesday, April 20, 2011

Puya chilensis, Bromeliaceae

A few years ago I was given some seed of Puya chilensis that germinated quickly and produced attractive small pot plants that had one particularly annoying trait. The arching whorls of leaves were fringed with vicious little recurved spines that were forever catching in my clothes or lacerating my skin, so one by one I gave them away to friends who had more space to grow them. On Tuesday, when I visited the National Botanic Garden of Wales I rather regretted that I hadn't been more patient, because their Puya chilensis had a magnificent three metre-tall flower spike. If I'd hung onto my plants for another decade, maybe............

.... or maybe not. I'd probably be permanently scarred by the Puya leaves by now, and you really need a glasshouse like that at the NBGW to flower this magnificent plant reliably. In the wild those recurved spines in the leaves have been known to impale birds and small mammals.

Puya chilensis comes from the coastal mountains of Chile and can be grown outside here in the mildest frost-free areas of Britain, such as the Tresco on the Scilly Isles. But what you really need is ......

........ a glasshouse like this - the magnificent structure designed by Sir Norman Foster for the NBGW.

This is the largest single-span glasshouse in the world, dedicated to displaying the flora of our planet's hotter, drier regions.

The stunning architecture of the building complements the natural architecture of the plants that it houses..........

........ while at the same time blending with its natural surroundings.

The glasshouse follows the contours of the land and reminds me of the carapace of a tortoise. A truely inspirational structure in an inspirational new botanic garden run by passionately committed, enthusiastic people.

Wednesday, April 6, 2011

Walnut, Juglans regia, Juglandaceae

When I was a kid my grandfather used to make little boats with half-walnut shells, fitting them with a matchstick mast and paper sail. Their association with childhood pleasures goes back a long way - apparently the Romans had a ritual at weddings whereby the bridegroom threw walnuts to children, symbolising the casting off of childhood preoccupations and the beginning of adult life.

One of the many botanically interesting aspects of walnuts is that they are not - botanically speaking - nuts. They are classified as drupes - fruits with a fleshy outer coating and a single hard seed inside, which groups them with peaches and plums whose outer coat is succulent. The tough outer coat of walnuts eventually splits to release the hard seed inside but it has its own special properties - it produces a deep brown dye. I discovered this for myself by accident when I was showing some visitors around Durham University Botanic Garden and picked up a fallen fruit and idly pulled it apart to show them the walnut seed inside - and it took three days for the brown stains to disappear from my fingers.

For about twenty years I had a walnut tree in my own small garden but it was foolish to plant such a fast-growing forest tree in such a small plot. It quickly outgrew the garden and I had to cut it down - and that revealed another interesting sensory aspect of the tree - its foliage and wood have a distinctive fragrance, that to me smells of apricots.
Walnut produces male and female reproductive structures separately on the same tree (monoecy) - the male flower being these fat catkins....

........... and the female being the ovary with a short style and twin stigmas that you can see between the leaf stalks at the top of the picture above. Solitary trees sometimes fail to produce nuts because there is a time differential between stigmas becoming receptive and the catkins shedding pollen (dichogamy).

Aside from its edible 'nuts', which were always an enduring feature of Christmas in our house when I was a child (no one could ever find the nut-crackers, which were not as elegant as the pair you can see here), walnut is famous for the beauty of its timber which is widely used for cabinet-making and for gun stocks. The tree originates from extreme south-east Europe and the Near-East (hence the alternative name Persian walnut) and can be killed in extreme winters. In 1709 there was a winter in Europe that killed thousands of walnut trees, which were felled and bought by Dutch merchants who foresaw an impending shortage and made a handsome profit by cornering the market for walnut timber in the years before new trees could be established.
There is an old saying that walnut trees are more fruitful if their branches are beaten. The likely origin of this is that walnuts used to be  harvested as soon as they began to ripen, while still attached to the tree, by knocking them down with long poles - otherwise birds and squirrels would get them first. This assault on the tree broke the tips of twigs and promoted the growth of fruiting spurs, producing a better crop of fruits in the following year.