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March 2016

Sycamore? Or sycamore?

American sycamore, Platanus occidentalis, growing on the New York side of the Delaware River. ©

Gardeners and botanists both use common names as well as scientific names when referring to plants. Using common names for plants is more widespread in North America than it is in Britain, even among botanists, and even though common names are often simply made up if there doesn’t seem to be one already in use. But common names are confusing. After all, there are more than twenty different plants, from around the world, that are called “bluebells”.

Native Americans must have had local names for many native plants when settlers first arrived in North America but the settlers didn’t bother to learn them and simply made up new ones - or, as with birds like the robin, transferred a familiar common name to a plant that looked vaguely similar to one from back home.

So when I saw a large mature sycamore (above) way across the Delaware River the other day, its white branches ghosting against the oaks and maples behind, I was reminded of this: in Europe, sycamore is used for Acer pseudoplatanus; here in North America sycamore is Platanus occidentalis. The leaves are very similar, so I presume settlers simply transferred the name. But surely, native Americans must have had a common name for P. occidentalis. After all, I’m told they used to tap it for sap in the same way as sugar maples.

In Europe, P. occidentalis is the plane tree and its hybrid with P. orientalis is a familiar city street tree. In Paris, large plane trees in the streets are pruned – literally – into a plane with all the branches parallel to the street and none overhanging.

The sycamore of Europe, Acer pseudoplatanus (below) - whose botanical name, by the way, literally translates as “the maple that looks like a plane tree”! - is a menace. There’s a huge one in our neighbor’s garden in England and its seedlings spring up all over the place. What’s worse is that they get their new roots down deep quickly so that even when they’re less than a foot high they can be tough to extract, especially between the cracks in paving.

I’d much rather have the American version.

European sysamore, Acer pseudoplatanus, growing at Parc de Mariemont in Belgium © Jean-Pol Grandmont. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
Acer speudoplatanus image (above)  © Jean-Pol Grandmont. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Australian pelargonium found wild in Britain

One of the most interesting features in the BSBI News, the magazine for members of the Botanical Society of Britain and Ireland, is the section headed Adventives & Alien News. This is where news of the more interesting non-native arrivals is posted.

In the current issue there’s news of two related plants very rarely seen in Britain, one so unexpected that it gets a short article all to itself.

The most surprising news is that Pelargonium inodorum (above), a native of Australia and New Zealand, and not grown in British gardens, has been found growing on the Isle of Wight - off the south coast of England. Spotted last September, it was happily flowering away on a sandy bank near a boating lake in the town of Ryde, across the road from the beach. It seems to have been there for a few years as there are large and small plants.

Interestingly, it is also said to have become established in California, but the California Native Plant Society has no records. So often, when a non-native plant turns up in the wild in America, the reaction is to discuss how to eliminate it. The Botanical Society of Britain and Ireland publishes records and monitors the continuing status of new arrivals so that any such decisions can have a scientific basis.

ErodiumTrifolium700As it happens, there’s news of a related plant that has also started turning up on the Isle of Wight. A heron’s bill that’s native to North Africa, Erodium trifolium (left), was first spotted near Dartford in Kent in 1999, but has now been found in two different places on the Isle of Wight. A large plant was found on an industrial estate and half a dozen plants on a mown roadside verge. That original find in Kent was described as “an extensive weed on walls and roadsides”.

This is a very attractive species which is grown in gardens and listed in the latest RHS Plant Finder as stocked by five nurseries, none of which are on the Isle of Wight.

Other interesting sightings mentioned in this latest BSBI News include:
* Portulaca oleracea, the kitchen garden purslane, native to India, established in two sites in different parts of Sussex;
* the drought tolerant Gaillardia x grandiflora naturalised on sand dunes in Kent and increasingly popular in gardens;
* purple-flowered Verbascum phoenicium, found in Staffordshire in the English midlands.

The point of all this is that recording these plants, and following their status over time, is the basic science from which conclusions can be drawn about their spread – or their disappearance. Indigofera hirsuta is considered invasive in parts of North America, but a plant of the closely related Indigofera heterantha found in Sussex in 2012 has since gone. We need to know when species do not spread as well as when they do. Ripping them out as soon as we see them tells us nothing.

Thank you to Peter Heenan of Landcare Research for permission to use his image of Pelargonium inodorum. The image of Erodium trifolium is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. Details here.