Friday, 20 January 2017

Major roads - a gap in recording coverage?

I've been thinking about gaps in record coverage of certain habitats or groups of plants in Oxfordshire, and this post is about one I believe exists — big roads. Future posts will cover other under-recorded areas. These posts will mostly cover non-native or other human-derived elements of our flora, and that these represent gaps perhaps suggests that Oxfordshire is a more conservation-focused county. Of course this is a good thing, but aliens also tell stories and make the human environment more interesting even if we'd wish they weren't there as conservationists.

Salted road adventives

Big roads are noisy, smelly and ugly, and it's understandable that botanists would prefer to avoid big them. However, I think that as a result our records have suffered: there are hardly any records of seaside plants, such as Cochlearia danica (Danish scurvy-grass), along our salted roads. One could argue that these salt-loving seaside plants (halophytes) are not a 'native' part of our flora and as we've so much else to do for local plant conservation and recording it's best not to worry about them. That's a justifiable position, but putting on my BSBI hat I'd reply that it's our job as recorders to faithfully document changes in vascular plant distributions, whether it's the declines in so many of our native plants, increases in non-native species, or charting the unforeseen weirdness of halophytes spreading inland along salted roads. 

So, which are the main species to look out for? The following five species are among the commoner maritime species found along roads. Other halophytes along roads include, rarely in V.C. 23, Malva arborea (tree mallow) and, also found on heaths and wasteground, P. coronopus (buck's horn plantain). Not yet recorded are Plantago maritima (sea plantain), and Sagina maritima (sea pearlwort). Cerastium diffusum (sea mouse-ear) was found along the M40 in 2016 by Roger Heath-Brown, quite uncommon this far inland.

Cochlearia danica (Danish scurvy-grass)

This little annual member of the Brassicaceae is easily recognised in April and May even travelling at 70mph, forming great sheets of white flowers along heavily-salted roads such as motorways. It will also crop up in small quantity along the bare edges of verges of minor roads.

This is the most widespread inland salt adventive, but Oxfordshire has the fewest records of this species of all the counties in England: 29 against Worcestershire's 872. Most records are from the last two seasons, but I find it hard to believe that this species has only just started to spread across the county. Evidently, recorders are not visiting places where Cochlearia is likely to be found.

Right: the spring-flowering Cochlearia danica with white flowers and small, heart-shaped leaves is a distinctive member of our salt adventive flora. Wikimedia Commons

Puccinellia distans (Reflexed Saltmarsh Grass)

This is a small loosely tussock-forming perennial grass with somewhat glaucous leaves. Growing in weedy situations in the gutters of roads it could easily be overlooked as Poa annua (annual meadowgrass) if one were unfamiliar with Puccinellia. However, like Cochlearia danica it can form extensive lawns along the edges of roads making it readily recognisable. The inflorescence is distinctive, looking somewhat like a very open Poa (meadow grass), with a pyramidal shape and small distant spikelets, but the lower branches are distinctly reflexed at maturity.

Of this species there are nine records known to me from the county, seven from 2016, and only Herefordshire has fewer in England. Please send me records!

Left: Puccinellia distans. Saxifraga

Spergularia marina (Lesser Sea Spurrey)

Oxfordshire also represents a big hole in the national distribution of Spergularia marina, another frequent annual along large salted roads. There is a quite a large population along the A34 between the M40 and Kiddlington where I've looked and I have no doubt it will be found elsewhere if searched for. Spergularia marina did of course once occur as a more natural component of the local flora at the salt spring at Marcham, modern day Oxfordshire, Berks (V.C. 22) for recording purposes.

Right: the English distribution of Spergularia marina with the vice county of Oxfordshire boundary overlain — no records!. There are now three Oxfordshire records from 2016, not shown. BSBI

This little pink-flowered member of the Caryophyllaceae could only be confused with other members of the genus, from which it differs in being annual, in its smaller flowers with eight or fewer stamens and seeds usually with a broad flattened rim. Vegetatively it looks somewhat like a pearlwort (Sagina), but  it is bright green and succulent.

Left: the pink-flowered annual Spergularia marina. Carl Farmer

Atriplex littoralis (Grass-leaved Orache)

This species is less frequent than the others: there are only three Oxfordshire records, two from 2016. It seems to be a species on the increase, much more prevalent inland in the east of England, but I'm sure there is more of it out there on our local roads. Oraches are common plants of roadsides, as they are on farmland. Most are either A. patula or A. prostrata, but A. littoralis is quite distinct from these, as its English name indicates: it has very narrow (though not really grass-like) leaves. Unlike other Atriplex species in Oxfordshire the leaves lack  any lobes. 

Right: the distinctively narrow-leaved halophyte  Atriplex littoralis. Wikimedia Commons

Tripleurospermum maritimum (Sea Mayweed)

Puzzlingly there are more records of this halophyte in the database than the total number of records of the above maritime species. The Oxfordshire records are not shown in Atlas 2000, nor in the county Flora and they must therefore be errors: the sea mayweed was formerly considered the same species as the similar scentless mayweed, T. inodorum. Sea mayweed differs in its fleshy leaf segments, but the most reliable character is in the achenes (right).

It'd be nice to know if T. maritimum did occur in Oxfordshire!

The fleshy-leaved sea mayweed with (inset) its achenes ('seeds') bearing a pair of elongated glands. Wikimedia Commons

Other interesting plants...

Large roads can also throw up many other interesting records. Recording along the A34 earlier this year turned up only the third record of Senecio inaequidens (narrow-leaved ragwort, right) in V.C. 23 and the fifth for the hybrid St John's wort Hypericum x desetangsii nothosubsp. desetangsii. Dittrichia graveolens is another species that may be spreading up the A34 in the county and roads are a frequent corridor for the spread of other aliens.

Finally, road corridors are also foci of tree and shrub planting, and while landscapers might think they're planting native species they are often not: weird dogwoods, wayfaring trees, maples and hawthorns are found very commonly in such places. Some native taxa are planted out of their natural context, e.g. sweet-briar. Records do not indicate the widespread occurence of these aliens in the county, but they must certainly be very much with us and will be the subject of a future blog post.


In summary, big roads can be really quite interesting, but how can we better record them? Some big roads, especially motorways, are not accessible to botanists and this is obviously a problem, as is that of safety. However, many of our regional roads are safely accessible — the footpaths along the A34, A40 and the Oxford ringroad spring to mind. How about the next time you record a square with a large road such as one of these in it that you make an effort not to dismiss it as uninteresting? Much is still to be learnt about our changing flora!

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