Settle Wildflowers Day 120: Prickly Lettuce - Lactuca serriola - in Langcliffe Quarry Enterprise Centre

I found this plant in August - a new one for our area (Langcliffe, Settle, Yorks Dales) - and was not sure if it was Prickly Lettuce Lactuca serriola or Great Lettuce Lactuca virosa. Both have spines on the midrib of the leaves.

Having put it on Twitter #wildflowerhour and elsewhere on social media (and having plumped for L virosa) I have now been informed

It is in fact L serriola - because "Virosa has obvious purple flushing in all parts but especially along stem and leaves. Serriola usually has whitish appearance."

I have now updated the rest of this post accordingly

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The old council yard and buildings at the Hoffman Kiln, Langcliffe gave me many new flowers in my 2020 list of  "Wildlfowers found on Lockdown walks." Sadly most are now gone -

Since then the buildings (except one) have been pulled down and new buildings , tarmac and paving stones erected on the "waste land". These buildings are now called Langcliffe Quarry enterprise Site.  The old footpath path amazingly close to the railway has been replaced by a new one a few meters back and a large grill now separates walkers from the old path and railway. New topsoil has been placed in the parts to be left as garden.

One new plant has arrived on these beds: (lots of old ones too, such as Broadleaved Dock, Spear and Creeping Thistle, various Oraches..)

The new plant has spines on the midrib of the leaves, has white latex and is..

Spiny Lettuce. Lactuca serriola

I struggled to work out whether it was Great Lettuce Lactuca virosa or Prickly Lettuce Lactuca serriola. Indeed I struggled to find it with the flowers out at all - it always seemed closed in in bud and closed in fruit.

Then I realised it must be like many others in that tribe of Lactuceae /Cichoreae - Such as "Jack Go-to-bed-at-noon" - Tragopogon pratensis. - that it must go to bed at noon.

So on Tuesday morning 13 Sept I trotted out again - at 7.30am it was in shade - then back at 10.30am, and the blue sky and intense sun the tiny yellow inflorescences were open and just two heads were in seed.







I took one seed head home and measured the achenes 

The white beaks on the achenes are the same length as the achenes.

They were 4mm to 4.3mm long and very dark brown almost black. So I  first made it L virosa. Some of the leaf stems had a hint of marron in them.

L serriola on the other hand is supposed to have achenes that are 3-4 mm long and are olive grey, and to have no hint of dark red in the leaves.

Well my advisors elsewhere who know the plants said the purple colour in the stems and leaves are important.

So L serriola it is

I took lots and lots of pictures.

There are at least four separate plants.. So I hope they will seed well and last at least till new people come to the buildings and do the flower beds.

The involucral bracts open out in a quite spectacular fashion. 

(I did actually pick this head so that I could hold it up to the light

... and very close to the camera)

There are pictures on the internet of  L serriola with much more lobed leaves and more clasping base of the leaf blades to that at a distance the plant looks more like Soft Sow thistle.. I shall have to investigate plants more carefully.

In an earlier Settle Wildflowers post -Day 68 I said that I had found 11 members of the (sub) tribe Cichoreae or Lactuceae around Settle plus 1 extra (Bristly Oxtongue) near Ripon. This now brings my total to 12 members around Settle (Plus 1 bear Ripon)

Below: some L virosa info:

Lactuca virosa

By Franz Eugen Köhler, Köhler's Medizinal-Pflanzen - <a rel="nofollow" class="external text" href="http://pharm1.pharmazie.uni-greifswald.de/allgemei/koehler/koeh-eng.htm">List of Koehler Images</a>, Public Domain, Link

See more "Wildflower Walks around Settle"