Tuesday, 27 May 2008

Acacia

Robinia pseudoacacia is known as Acacia in France. Of course, as a good Australian, to me this tree is False Acacia. Real Acacia or Wattle, is Australia's national flower, and in France is called Mimosa.

A couple of years ago the taxonomy police mounted one of their regular campaigns to split the genus Acacia which would result in many being renamed. The type species ie the first Acacia to be scientifically described, is in Africa. Traditionally, when renaming and splitting of a large genus occurs (there are about 1300 species of Acacia worldwide) the type species is the one to retain the original name. But there are precedents, when there are good arguments against going with 'tradition', where the type species fails to retain the old familiar name and it goes to a more newly described species. Many Australian botanical taxonomists, and indeed, many ordinary Australians, outraged by the thought having to refer to Racosperma, argued successfully to the International Botanical Congress that as Australia has about 1000 of the world species, it made sense that the largest genus in the reclassification should be allocated the coveted name. Part of the reasoning behind this was entirely pragmatic - it is a time consuming and expensive process renaming herbarium specimens and what about all those field guides and gardening books put instantly out of date, if not obsolete?

However, all of this is a distraction from the main topic at hand, which from now on I will refer to by its 'proper' name of Robinia. In the UK it used to be known as Black Locust, or often, just Locust Tree. Where we live in England is in what is called a 'Conservation Area' (meaning that the village has many buildings of architectural and historic significance, and permission must be sought to make alterations to ensure the area is maintained sensitively). This protective regulation doesn't just cover the buildings and infrastructure. Many of the older and more impressive trees are 'listed' and (theoretically) cannot even be pruned without permission, much less cut down. A number of the listed trees in our area are Robinia, but it took me a while to figure this out. The listing was done in the 1960s, and surprisingly, scientific names were not used. Our Robinia are listed as Locust Trees, and as an Australian, a Locust Tree to me is Gleditsia triacanthos, a plant that is classified as a noxious weed, as it self-seeds so readily and escapes into the bush. No wonder I was confused.

A Robinia in the churchyard next to our house in England, taken early one winter morningRegular readers of our blog may be interested to know that Robinia pseudoacacia was introduced to the UK c1630, the same time as Cedar of Lebanon. Like Cedar of Lebanon, Robinia came to France earlier than to England. It arrived sometime before 1606 and was grown by the royal gardener Jean Robin. It is very fitting that the tree now bears his name, as by the time it was introduced to England (as a gift from Robin to John Tradescant Senior) it was thriving in the Louvre garden established by Henri IV and as those familiar with the French countryside will know, is now naturalised throughout France. It flowers May-June, and veils many a French woodland in its fragrant white clusters of pea-flowers.

Robinia casting its haze of flowers over the woodland across the river from Yzeures sur CreuseWhen it was first described it was classified as a Mimosa and named Acacia americana Robinii (it is native to North America). The flowers are very attractive to bees and miel d'Acacia is a very popular and widely available mild tasting honey in France. Always one of the last trees to come into leaf in the spring, in the autumn they turn yellow. It turned out to be very tolerant of smoke and soot, so it was a popular park tree once the industrial revolution kicked in, and was frequently planted on railway embankments.

Robinia dangling over a disused railway line which is now a vélorail trackTo complete the rather circuitous nature of this narrative, I would like to add that when I was a child we lived on a farm in the Australian state of Victoria. In the home paddock there were two enormous and spreading False Acacias. I remember these as by far the biggest Robinia of my acquaintance, but, having never seen these trees after moving away, it is difficult to know if this is just a trick of childhood memory.

Susan

3 comments:

  1. Extremely interesting post and, consequently, I'm extremely confused, not by what you are writing but why the tree is
    called "pseudoacacia".
    You say, and I quote : "When it was first described it was classified as a Mimosa and named Acacia americana Robinii (it is native to North America)."
    Why the name was changed from something to false something is beyond me.
    It is or it is not an acacia, so let's drop the pseudo thing and call it Robinia melliflora, and be done with it?
    I navigated for hours in the mimosa, acacia and pea choppy waters and the shore is still out of sight!

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  2. R melliflora is an excellent choice - let's mount a campaign and run it by the IBC :) I expect the pseudoacacia epithet was the result of a botanist with Grumpy Old Git Syndrome, fed up with 'his' tree being constantly referred to as a Mimosa, when he'd done years of research to establish that it was a Fabiaceae.
    Susan

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  3. It's nice to see the black locust getting its due. Locusts here (Pennsylvania) are fairly short-lived trees, but their wood is useful for fenceposts since the wood doesn't rot in damp soil. High BTU content makes their wood suitable for heating; it's a staple in our woodpile. Because they don't grow very big, a 7' section of trunk isn't too heavy or thick for me to drag to the tractor.

    When the trees flower, you can see just how many there are on the hillsides. Unfortunately, locust borer hits them hard in some years.

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