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Tuesday, November 29, 2011

California flannel bush, Fremontodendron californicum, Malvaceae

Until the harsh winter of 2009-10 I had a 3m. tall specimen of this lovely Californian shrub growing in my back garden, but sadly the severity of that winter killed it and I haven't yet got around to planting another. It comes from the foothills of the Sierra Nevada, thriving in nutritionally poor soil - which explains why it did do well when it was rooted close to my leylandii hedge, in a very dry spot where nothing else will grow. It's also a good wall shrub, doing well in the rubble around the foundations of a house and trained against a south-facing wall.

The flowers are interesting because, like those of hellebores, the parts that look like petals are actually the sepals - there are no true petals.

It's a very prolific producer of nectar (you can see nectar drops glistening in the image above) so bumblebees love it. 

You do need to be careful when you prune the plant though, because the densely hairy stems and leaves (which account for its name of flannel bush) can cause skin irritation. The cultivar that's most often sold in Britain is usually labelled California Glory.

The plant has traditionally been classified in the family Sterculiaceae, but modern phylogenic studies by the Angiosperm Phylogeny Group, based on DNA sequence data that gives a more accurate reflection of evolutionary relationships, place it in the mallow family - the Malvaceae. Gardeners, and sometimes even professional botanists, often deplore the way in which plant scientific names and classification change so often but they shouldn't - it reflects the fact that someone, somewhere is still taking an interest in the world's flora and that traditional taxonomic botany isn't totally moribund in universities.

Fremontodendron, also know under the synonym of Fremontia, was first discovered by General Fremont near Sacramento in 1846 and was named after him - you can read an account of the colourful life of this soldier, explorer, anti-slavery campaigner, politician and plant collector here.  

Thursday, November 10, 2011

Water hyacinth, Eichhornia crassipes, Pontederiaceae

Water hyacinth Eichhornia crassipes is often rated as one of the world's top ten worst weeds, thanks to its prodigious capacity to spread over the surface of lakes and rivers. It's said that just one plant can multiply to cover an acre of lake surface in eight months, thanks to its ability to produce stolons that sprout new plants from their tips. While vegetative spread explains its local abundance, its short-lived but beautiful flowers have also played a part in its current worldwide distribution in the tropics. It comes from South America but is now a problem in Africa, India and the Far East where it has been introduced as an ornamental species that has quickly rampaged out of control. It carpets parts of Lake Victoria in Africa, impeding navigation,  and within a year of being introduced onto the Sudanese Nile in 1957 it had spread along 620 miles of river.

Water hyacinth isn't hardy in Britain, although there were a couple of reports of it surviving outside through the winter in Norfolk a few years ago. The last two severe winters would certainly have killed any plants in garden ponds, but it does make an attractive plant for a conservatory. Here it's sharing its indoor pond with another notorious aquatic weed, water lettuce Pistia stratiotes, which is equally prolific.

Water hyacinth owes its buoyancy to these inflated leaf petioles. When you cut these open ...

... you find that they are sub-divided into hundreds of small, rectangular compartments with thin walls of papery cells.

Although water hyacinth is a problematic weed there's a lot of research going in into useful applications of this plant. These include bioremediation - using its capacity to absorb and sequester toxic metals like mercury, chrome, lead, cadmium, zinc and arsenic via its fibrous root system that dangles in the water. Numerous trials have been carried out for waste water treatment. It has also been used as animal feed (from plants grown on clean water) and there's extensive research into using its rapid biomass production as a source of energy, by using the harvested plants to produce biogas or bioethanol.

Wednesday, November 2, 2011

Rose grape, Medinilla magnifica, Melastomataceae

Rose grape Medinilla magnifica is high on my lamentable list of 'plants that I wish I'd taken better care of'. I bought one in the spring, it flowered well through the summer, struggled through a winter in my cool  conservatory, had a final flourish of flowering in the following spring then keeled over and died. But while it lasted it lived up to its specific name and was truely magnificent. It's an excellent plant for growing in a pot on a high shelf, so that you can look up and appreciate its spectacular dangling inflorescences.

Medinilla magnifica is native to the island of Luzon in the Philippines, where it often grows as a large epiphytic shrub on trees. I visited Luzon a couple of times about 25 years ago, without being lucky enough to see it flowering in its native habitat - but if I could afford a fully heated conservatory with supplementary lighting in winter, it would be first on my list of plants to acquire again.
The Melastomataceae is a tropical family - you can find more on another member of the family that's much easier to cultivate as a house plant here.