Perennial Rocket in Heaton Mersey

Last Saturday (22.08.2009) the regular Manchester Field Club walk was at Mersey Vale, Heaton Mersey. Several interesting plants were encountered including French Hawksbeard (Crepis nicaeensis), Sand Spurrey (Spergularia rubra) and a few other slightly obscure ‘treasures’. As you can imagine this was just up my street!

As it happens I was the walk leader and I had chosen this walk for its botanical interest. I had done a number of reconnaissance visits in the previous few months and knew that a walk with fellow enthusiasts was likely to be interesting and productive. Mersey Vale is a ‘linear’ park so any walk is basically ‘there-and-back-again’. On the return trip I spotted the remains of a plant that I had noted in flower on a previous visit back in June. I had determined that this plant was Perennial Rocket (Sisymbrium strictissimum) – which is, if anything, even more obscure than some of the other species that we found on last Saturday’s walk. It is an introduced plant, native to central and eastern Europe, from France and Italy eastward to Russia and Bulgaria (ref. 1). How it became naturalised in a few places in England, from Durham to Surrey (ref. 2), is not at all clear. Seeing it again jogged my memory. Back in June I had meant to look something up but hadn’t managed to get round to it. So I now found the entry for S. strictissimum in ‘Travis’s Flora of South Lancashire’ (ref.3 –Note that Heaton Mersey may be in Stockport, and hence in Cheshire, but for botanical recording purposes it is in Vice County 59, South Lancashire). The note read: “On land surrounding the Mellard and Coward bleach-works at Heaton Mersey ... First Record about 1890, Bailey (1905)”. An interpretation board near where I found the plant informed me that the nearby modern industrial estate had once been a bleach-works and other members of the Field Club confirmed this.
So it would appear that Perennial Rocket had been growing in that small area for at least 119 years! I wonder how long it had been there before that?

‘Bailey’ refers to Charles Bailey (1838 – 1924), an amateur botanist who also happened to be a rich Manchester businessman. He took up botany after attending a series of evening classes given by William Crawford Williamson who was Professor of Natural History at Owen’s College (later Manchester University). Bailey amassed a private herbarium containing some 300,000 specimens of mainly European plants which, on his death, was bequeathed to Manchester Museum and now forms an important reference collection. Many of these (pressed, dried, labelled and mounted) specimens were purchased via auctions but he does seem to have done some collecting himself in the South Manchester area. He also seems to have been intrigued enough by his Perennial Rocket find to write a paper about it for the Manchester Literary and Philosophical Society (Bailey, C., 1905. Notes on Sisymbrium strictissimum at Heaton Mersey, Man. Lit. Phil. Soc. Proc.). I’ve not seen this paper but must see if I can find it in Central Library.

The name ‘Rocket’, by the way, is applied to a number of members of the Cabbage or Mustard family (Brassicaceae). ‘Rocket’ seems to be derived from the word, ‘eruca’ that the Romans used for the peppery, somewhat bitter herb which is now a trendy (although beginning to slip out of fashion) salad ingredient, the scientific name for which is Eruca sativa (or Eruca vesicaria subsp. sativa - depending upon which expert you consult): “Just drizzle it with a little balsamic vinegar dressing, darling!”

I don’t know whether you can eat Perennial Rocket (with or without balsamic vinegar dressing) but, as with all wild plants, I’d thoroughly check its toxicity first. On the other hand it is quite rare so that’s another reason for not dining on it!

References:

1. ‘The Wild Flowers of the British Isles’ by Ian Garrard and David Streeter, Macmillan, 1983.

2. ‘New Flora of the British Isles’ by Clive Stace, Cambridge University Press, 1st Ed., 1991.

3. ‘Travis’s Flora of South Lancashire’, Eds. J.P. Savidge, V.H. Heywood & V. Gordon, Liverpool Botanical Society, 1963.