28-3-2016
My sister Pip and I went walking today in the sunny, breezy aftermath of a storm which had battered Devon with 70 mph winds and driving rain the night before. Salcombe has interesting routes for walkers to choose from: pretty, high-banked lanes that loop inland through woods and secluded coombes, or climb to bald summits with panoramic views; coastal paths that go tracking out round the estuary's gentle indentations or threading boldly the harsh, sea-girt declivities of Bolt.
There are also paths in the town where the nature of Devon and far-off places are mingled in startling southern conjugations. Wooded slopes too steep for houses show a native flora of oak and hazel, pennywort and primrose enriched by all kinds of exotic garden escapes. The mild oceanic climate means that local gardeners can be adventurous with their choice of plants: one of the footpaths is overhung with a pineapple palm (Phoenix canariensis) from the Canary Islands. Southern species such as the holm oak (Quercus ilex) may last have been native here 10 million years ago in the Miocene, when subtropical forest covered Britain, including elements of the beautiful laurissilva now found in the Macaronesian group of islands off the African coast (e.g. Madeira, Tenerife, Cape Verde). They were later pushed south by advancing Pleistocene ice sheets, but have now returned - with human help.
My most joyous discovery has been the tree echium, Echium pininana, from the Canary Islands. As we followed a wooded path we came upon spectacular, long-stalked, bushy plants, rather like dark-green shaggy clubs. Dried woody remnants of last year's dead stalks towered alongside us, reaching well above head height.
Tree echium has an interesting story, recently deciphered by botanists using molecular genetics [1]. The genus Echium originated as a herbaceous plant living round the Mediterranean, then spread to the Macaronesian islands when they formed, one after the other, by volcanic action over the last 20 million years. As Darwin and other have noted, herbaceous plants on islands tend to evolve a woody growth habit, so a new range of woody Echium species evolved in Macaronesia, able to grow to a remarkable height. Echium pininana is one of them, an endemic of La Palma in the Canaries. Research shows that it arrived in the Pliocene epoch about 3.73 million years ago [2].
I have never visited the Canary Islands, but I have been captivated by photos of their enchanting forests, volcanic mountains and luminous atmosphere. They are on my life's list of places to visit. I would not be put off by the thronging coastal holiday resorts; they'd just be a cheap place to roost in between day excursions to explore the vegetated, rocky interior. If I were on La Palma I'd make a point of seeking out Echium pininana. It is not too late for me to do it.
Tree echium is a monocarpic plant. That means it flowers once then dies. It lays down wood then builds itself up over two or three years before spending itself in one final, magnificent, spire-shaped spasm of mauvy-blue flowers. I may never make it to the Canaries, but I'll be happy to visit Salcombe again one July or August to catch Echium pininana at its moment of Macaronesian glory. The plants I saw this week look as though they are preparing themselves for a mighty show.
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| Echium pininana photographed on Guernsey. Image courtesy La Société Guernesiaise. |
References
1 - Bohle, U-R et al (1996): Island colonization and evolution of the insular woody habit in Echium L. (Boraginaceae); Proc. Natl. Acad. Sci. USA, Vol.93, pp.11740-11745/.
Online at: http://www.pnas.org/content/93/21/11740.full.pdf [April 2016]
2 - Kim, S-C et al (2008): Timing and Tempo of Early and Successive Adaptive Radiations in Macaronesia; PLoS ONE. 2008; 3(5): e2139.
Online at: http://europepmc.org/articles/PMC2367450#pone.0002139-FranciscoOrtega2/. [April 2016]
