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.

Mad Dogs ...

 ... and botanists go out in the mid-day sun on the hottest day of the year so far. Crazy, but I'm not one for wasting sunshine (I live in Leeds after all), especially after a spring lost to covid and excessive rainfall. So, I took one of my lazy weekend routes out along the shade of the river corridor towards Mickletown (VC63) and then back via St Aidan's (VC64).

Over the winter the Canal and River Trust had cleared a path through the woodland on the river bank near Lemonroyd Marina (VC63). This new route gave me the first good find of the day - several bushes of the irredeemably pungent Stinking Tutsan (Hypericum hircinum subsp. majus). A new species for my home patch.

Further on was a bush of hazel yet to be stripped of its nuts by voracious grey squirrels. This is one of the hybrids between the native Hazel (Corylus avellana) and the Filbert (Corylus maxima). This form could be easily mistaken for the latter but the involucre is not fully closed over the nut and consequently the nut is visible. This would key*, given the nuts are obviously longer than wide, to the form Peter Sell distinguished as Corylus avellana f. schizochlamys. However, the length of the involucre and the pronounced pinching over the nut means it is not a good match. It looks to have much more of an influence from Corylus maxima than is typical for this form.

Further on, and handy for comparison purposes, I found another bush likely to be part of this hybrid spectrum. Its a common form with very large nuts that are about as long as wide. Under Peter Sell's classification it can be called Corylus avellana f. grandis. Again the involucre exceeds the nut, which is a trait potentially derived from Filbert.

Out in the sun near Mickletown (VC63) there was an impressive mixed stand of Broad-leaved Everlasting-pea (Lathyrus latifolius), a garden escape. The pale-flowered plants seems a good match for the cultivar 'Rosa Perle', while the darker ones seem to be 'Red Pearl'.

Next to the pea was a distinctive bramble. This being, Slender-spined Bramble (Rubus elegantispinosus), a species that I learnt under lockdown last year. Baby steps with this genus. I remain ever hopeful for a regional handbook with photos.

The final treat of the day was the swathes of Hare's-foot Clover (Trifolium arvense) lining the track through St Aidan's (VC64). This species has exploded in numbers in recent years and is always a welcome sight.

* Update: I would modify this to accords with the pictures in Sell & Murrell. The descriptions seem back to front with the pictures. While it would be tempting to rely on the descriptions, I am also swayed by the description of var. grandis (the "big round nut" as originally defined in its latin diagnosis) in this account (European Journal of Taxonomy 409(409):1–45). This also seems to indicate that f. schizochlamys is not correctly applied in Sell & Murrell. All this is possibly academic given the more you look, the more variation can be found. It seems likely that these named forms only represent a tiny proportion of the true variation of this long cultivated tree, and at best are only loose groupings. I am increasingly inclined to take the stance of Alan Leslie in his excellent Flora of Cambridgeshire.

Lapsana communis subsp. intermedia

So the excitement this week, while out on a work survey at South Hetton (VC66) with aspiring ecologist Harriet Duffield*, was this non-native form of Nipplewort (Lapsana communis subsp. intermedia). I don't know who was more excited, me or Harriet**. The BSBI database shows that it has been recorded from the county previously, but this is a new hectad.

It stands out with its large bright golden flowers (I was expecting it to be a hawkweed), but it also has very distinct foliage. I see that Stace 4 has dropped mention of the lateral lobes on the leaves being nearly as wide as the terminal lobe, which is mentioned in other sources. Even so, when compared with subsp. communis, the leaves are very distinct. I was also interested to see that some plants are completely glabrous, while others have either hairy stems and leaves, or just hairy leaves.

subsp. intermedia on  the left, subsp. communis on the right

* That's for saying that you would never get a mention on my blog! And yes I do know that's not how you spell inspiring.

** Ok I do.

Daffodils

This is becoming an annual spring obsession now but its amazing how many you can clock up over the period March to May (none are in flower in February in Leeds, not even 'February Gold'). I only concern myself with those found in woods, on river banks, areas of waste ground, unmanaged churchyards and similar situations, deliberately steering clear of urban road verge plantings. Accordingly, I tend to find mainly the old tried and true cultivars that are tough as old boots, so largely pre-1940's or exceptionally pre-1970's. 'Oxford Gold' with a registration date of 2007 was a complete surprise this year, popping up in an obscure part of the churchyard after last years clearance of brambles.

Highlights from this years haul (with date of registration) include:

Actaea (<1919)                                            Aranjuez (1932)

                                                                                             Barrett Browning (1945)                           Bath's Flame (1913)

Beersheba (1923)                                        Dick Wilden (1962)

Carlton (1927)                                            Conspicuus (1869)

Delibes (1950)                                            Double Sir Watkin (1916)

Dutch Master (1948)                                   Emperor (1869)

Empress (1869)                                           Feu de Joie (1927)

Flower Drift (1966)                                    Flower Record (1943)

Fortissimo (1964)                                       Glenfarclas (1976)

Golden Harvest (1920)                               Gulliver (1927)

Ice Follies (1953)                                        Itzim (1982)

Jenny (1943)                                               Jetfire (1966)

Magnet (1931)                                            Maximus (1576)

Mount Hood (1938)                                    Oxford Gold (2007)

Pomona (1930)                                           Princeps (<1830)

Ptolemy (1921)                                           Sempre Avanti (1938)

Sir Watkin (<1868)                                     Spellbinder (1944)

Stella (<1869)                                             Sulphur Star (<1869)

White Lady (<1897)                                   White Lion (<1949)