Knapweed Novelties

Shortly after completion of construction of the A1(M) east of Leeds in 1999, the verges and road junctions in the vicinity of Aberford and Hook Moor (VC64) became briefly notable for unusual flora. Most especially, for the knapweeds that established from the seed mixtures used to 'restore' the affected landscape. Chief amongst these was Panicled Knapweed (Centaurea rhenana), a delicate airy species from mainland Europe. Its had a name change since then and now goes by Centaurea stoebe subsp. stoebe. It only really came onto my radar when Mike Wilcox re-found it in 2019, a remarkable 20 year persistence for a species still not listed in Stace or any other British Flora. 

So finally, I made a conscious decision this weekend to pick an area of promising habitat near the motorway to see if I could find it. And I did. What was even better was that the location I chose to search is a new one. The plot has also recently thickened with Mike advising me that the true identity was likely to be a related subspecies that is widely known as an invasive species in Europe and North America. This is Spotted Knapweed (Centaurea stoebe subsp. micranthos), a species it runs down to nicely in a key I found online.

The verges of the A1(M) between Garforth and Aberford are also a dependable hunting ground for Brown Knapweed (Centaurea jacea), although it is vastly outnumbered by its hybrid with the native Slender Knapweed (Centaurea debeauxii subsp. nemoralis) i.e. Centaurea x monktonii. Based on the situation in West Yorkshire, this hybrid must be widely overlooked elsewhere within the core range of Slender Knapweed. One to look for in modified landscapes where knapweeds have been introduced in the past.

More unexpected after the above was a robust knapweed well off flowering but with well developed buds with feathery recurved phyllaries. This seems to be Centaurea oxylepis, which will have also derived from the original sowing some over 20 years ago.

The final good find was two new locations for an alien Greater Knapweed first found by Mike to the north of Aberford in 2021, which we came to the decision (based on limited online sources) was a good match for Centaurea scabiosa subsp. alpestris. This is a striking species with, when compared with the native subsp. scabiosa, very variably dissected yellow-green leaves, and larger capitula with a much more prominent (but variable, even on the same plant) black apex to the phyllaries.

September Highlights

A few odds and ends in a post I never got round to finishing last year. Starting with these two unexpected finds by the stables at Royds Green (VC63) - Marrow (Cucurbita pepo) and Pumpkin (Cucurbita maxima).

On an uncultivated arable field at Aberford (VC64) Niger (Guizotia abyssinica). Also found by Mike Wilcox on river shingle at Apperley Bridge (VC64).

Also at Aberford, it was great to refind Wild Liquorice (Astragalus glycyphyllos). This is another rarity of the magnesian limestone that has not been reported for many years. Just a shame I missed it in flower.

Bringing some 'autumn joy' to the local bee population - Hylotelephium (Sedum) 'Herbstfreude' at Rothwell (VC63).

 

Arum 'Chameleon'

My serious plant hunting got off to a good start this weekend with this stunning Lords-and-Ladies cultivar emerging from a hedge in Ben Rhydding. Arum 'Chameleon' is a relatively new cultivar, so its not one that I would expect to be planted (this plant was emerging out of the church boundary hedge) or to self-seed true to form.

The consensus seems to be that this cultivar is likely to be derived from a cross between the native Arum maculatum and the non-native Arum italicum subsp. italicum (increasingly commonly naturalised). However, no one knows for sure.

Greater Musk-mallow

It was great to find Greater Musk-mallow (Malva alcea) again yesterday, still clinging on in the road verge at Newton (VC64) where I first found it in 2013. This relatively uncommon garden escape looks like it still has another month's worth of flowers yet to come. A welcome sight at a time of year when many other species have gone over.

Where there's muck,

there's goosefoots. Perhaps a bit harsh, but there is a fair chance of finding something interesting if you poke around the fringes of a muck heap. As was the case this week when I was rewarded with a strong colony of Grey Goosefoot (Chenopodium opulifolium) near the stables at Royds Green (VC63). Its one of those species that is relatively distinctive once known but very difficult to identify with confidence using a key. Handily, it is also a species that seems to have been collected widely in the past, so there are lots of good quality herbarium specimens to be found online (photographs on the other hand seem far less reliable).

Its seems to be a relatively short (to 30cm tall) and well-branched plant with small distinctively shaped leaves (with most about as wide as they are long). It was recorded widely in the past, but there are virtually no contemporary records. Lost or just overlooked?

A number of the plants had this yellow marbling to the leaves, contrasting with other species nearby. I'm not sure if its viral or a nutritional problem, but not something to otherwise pay too much regard to.

Micklefield Circular (VC64)

This Saturday finally promised a day of reliably dry weather, so I decided to make the most of it by exploring the limestone country to the east of Leeds. It is not a well botanised area as first impressions are of an intensively farmed landscape, which it is, but there are also extensive woodlands, relicts of limestone grassland, pretty villages where cottage gardens overspill their boundaries, and the arable fields themselves are not without surprises. Bravely, I ending up deciding on a 16km route from Micklefield to Sherburn in Elmet, South Milford, Lumby, Ledsham and back to Micklefield. But the walking was easy and relatively flat and, while I did not find any really good arable fields, I found lots of interest.

Things got off to a quick and excellent start in Micklefield when I found Green Nightshade (Solanum nitidibaccatum) next to the path past the new housing development. This species was virtually unknown in the county 5 years ago, but it has been turning up on light soils in the east of the county. I'm not sure if its a new colonist, or if it has just been missed. The plants here probably arrived with the sand used to construct the path. I found this species again later in an arable field in South Milford.

Heading away from Micklefield along the footpath towards Huddleston Hall I was surprised to find the wheat crop (an unusual awned form) over-topped by thousands of Rye (Secale cereale) plants. I assume it came in as a crop contaminant rather having been a crop in a previous year. I've never seen it grown at field scale locally, this being premium wheat and potato country.

Along the boundary of Huddleston Old Wood a bramble caught my eye. On first glance I thought I had found a pink-flowered Soft-haired Bramble (Rubus vestitus) (also, and more usually, available in white), one of the few bramble species that is relatively easy to both recognise and remember. This species has rather distinctive near-circular terminal leaflets with a thick fuzzy texture. However in this case, the leaves turned out to be rather thin and without the expected pubescence. Instead they were bright chalky white underneath. This and the vibrant pink-flowers indicated a hybrid with Elm-leaved Bramble (Rubus ulmifolius), another obligingly straightforward species. Hybrid status was also suggested by the poorly developed fruit, with only a few druplets swelling. A shame, as both parent species produce good fruit.

My journey down Laith Staid Lane towards Sherburn in Elmet rewarded my with one of my favourite plants, Deadly Nightshade (Atropa belladonna), in two discrete locations. Just a shame that it was past flowering (just one tatty flower left). But there is no mistaking that large foliage. 

Heading further down the lane my eye was drawn to some typical limestone grassland species clinging on in rough grassland on a nutrient enriched bank. Looking more closely I was surprised to see several large plants of Cat-mint (Nepeta cataria), a real rarity and last reported for the county no more recently than the 1990's. As all previous locations and associated details are very vague (somewhere in a 2km grid square in a 20 year period is the best we have), it was good to get a detailed grid reference for this location. Its to be hoped that it still persists elsewhere; maybe someone else will get lucky and find it.

The final interesting find along this lane was this enormous hogweed, easily 2m tall and towering over the adjacent hedgerow. An impressive plant, with the leaf in the bottom right of the photo probably as tall as a normal Hogweed (Heracleum sphondylium) plant. This is the taxon given in Sell & Murrell as Heracleum branca-ursina, but with the comment that it needs further research. It almost certainly does not merit full species status, but for the time being its the only name we have. In reality it is probably just a very distinctive, and likely alien, variety or forma of Hogweed.

On the outskirts of South Milford I came across this unusual form of Feverfew (Tanacetum parthenium f. breviradiatum).

And then further into the village in the roadside gutter of Woodside Close was Sea Campion (Silene uniflora). It must have escaped from a garden somewhere nearby.

But the best was yet to come, with an area of block paving on the High Street yielding a colony of American Cudweed (Gamochaeta purpurea). This seems to be the first record for Yorkshire.

Further unexpected aliens turned up at the end of Redhill Lane, Lumby where presumably the landowner dumps their garden waste. A search amongst the ruderals resulted in, in sequence, Thorn-apple (Datura stramonium), unfortunately not yet flowering, Common Millet (Panicum miliaceum), False Virginia-creeper (Parthenocissus inserta), and oddest of all a variegated Hosta (Hosta 'Undulata Albomarginata').

Crossing under the motorway to Selby Fork I was back to interesting native species, with a good stand of Juncus x diffusus, the hybrid between Soft Rush (Juncus effusus) and Hard Rush (Juncus inflexus).

By now I was starting to flag, but with Ledsham the next stop the end was almost in sight. Passing through the village a flash of colour in a ditch proved to be an attractive cultivar of Russian Comfrey (Symphytum x uplandicum 'Variegatum').

And then in Ledston Park, another nice native that is quite rare in the county. I suspect in this instance this Dark Mullein (Verbascum nigrum) may be a garden escape. It was not in typical habitat and was growing near Balm (Melissa officinalis).

All in all not a bad haul for the day. Definitely worth the leg work.

Odds and Ends

A few interesting plants that never made it into a specific post over the last few months...

Hairy-fruited broom (Cystisus striatus) found naturalised at a new site near Cridling Stubbs (VC63).

It was nice to find good numbers of truly Wild Pansy (Viola tricolor subsp. tricolor) near Rossington (VC63). Not a common sight on arable margins these days, and interesting to see so much variation in flower colour and form.

At the same location I was also surprised to find a thriving population of Yellow Bartsia (Parentucellia viscosa)

Siberian Wallflower (Erysimum x marshallii) popped up again in its usual spot in Woodlesford (VC63) where it was first sown several years back. Its one of those plants I was aware of but did not appreciate how different it was. Lots of years needlessly pondering any vaguely orange Wallflower (Erysimum cheiri) just in case!

A flash of gold(ish) in Little Preston (VC64) turned out to be Bowle's Golden Grass a cultivar of Wild Millet (Milium effusum 'Aureum'). Unfortunately, I never did get to see it flower, as the strimmers got there first. I'm surprised this grass is not more frequent, as it breeds true and self sows around my garden.

While on the edge of a farm ditch near Swillington, this stunning and unexpected Crown-Imperial Fritillary (Fritillaria imperialis 'Rubra Maxima') with other garden throwouts.