The Dandelion King

I recently found myself in Portree with half an hour to spare so, never being one to waste an opportunity, I set off to find a dandelion to key through using my copy of the recently published BSBI Field Handbook to British & Irish Dandelions. I can spend whole days in the hills and not see a flowering dandelion, but it's a different story in a town and it didn't take too long to track down a suitable dandelion. I papped the heck out of it, covering as many angles as possible, made a note of the habitat and grid reference, sliced it off at ground level with a knife (the taproot will survive this process and will continue to put up new growth) and popped it into a ziploc bag, ready to key through the following day.

Growing on the near vertical side of a shallow roadside ditch

Only partially open flowerhead, but it was the best example I could find

Note how the lowest few leaf lobes have toothed margins

Eye-catching lobes on the leaves, they reminded me of bluntly rounded arrowheads

The first thing to realise with dandelions is that there are some 240 species in Britain and, at first glance, they all look frighteningly similar to each other. The second thing to realise is that there's an easy method that will help you whittle those 240 species into a more manageable number. Well, maybe not 'easy', but certainly doable provided the dandelion is in good shape, is flowering, hasn't been trampled/mown/grazed, isn't heavily shaded or otherwise stressed and you're looking at it in the springtime through to mid-summer. Oh, and you need the handbook. Otherwise forget it. 

To get a dandelion to species you first have to work out which section it belongs to (there are nine sections in the British flora) and then key your way through the species in that group. The bulk of this post will be highly abbreviated versions of the handbook's keys accompanied by images that hopefully show you the various features mentioned, eventually working our way through to a specific identity. I'm not saying it'll be professional (because it certainly won't be!) but hopefully it'll be educational and might even get you thinking about tackling your own local dandelions.

First we need to figure out which of the nine sections of dandelion (Taraxacum) our plant belongs to. Unsurprisingly, the first key in the handbook is the Key to the sections of Taraxacum found in Britain and Ireland. I'll run our plant through it and highlight the option that works best in red. If anybody reading this has red-green colour blindness, drop me a comment and I'll change the colour. Otherwise I shall carry on in red.

1) Plants delicate, usually strongly dissected leaves, outer bracts rarely >7mm, capitula <30mm >>2

1) Plants medium to robust, outer exterior bracts >7mm, capitula usually >30mm when fully open >>3

Outer exterior bracts are >7mm and, were it fully open, the flower would be c50mm diameter

3) Leaves linear to lanceolate, shortly lobed to unlobed, exterior bracts appressed >> Palustria

3) Leaves broader, usually distinctly lobed, exterior bracts appressed to reflexed >>4

4) Leaves simple, smooth and flat, capitula deep orange, rare plants of Scottish cliffs >> Crocea

4) Lowland plants, or if in mountains leaves dark, hairy and often crisped >>5

5) Exterior bracts appressed, ligule stripe usually red, pollen usually absent, uplands >> Spectabilia

5) Exterior bracts various, ligule stripe usually solid, not red, pollen absent or not, various habitats >>6

6) Leaves with dark spots on upper surface, pollen often absent >> Naevosa

6) Leaves lacking dark spots above, pollen often present >>7 (through a microscope I could see pollen)

7) Outer exterior bracts >10mm, leaf mid-rib solid green or solid red to purple >> Taraxacum

7) Outer exterior bracts rarely >10mm, leaf mid-rib interwoven red and green strands >>8

8) Exterior bracts arcuate, lateral leaf-lobes usually hamate, pollen present, common plants >> Hamata

8) Exterior bracts usually straight, lateral leaf-lobes not hamate, pollen often absent >> Celtica

We need to understand what 'arcuate' and 'hamate' mean before progressing through that particular couplet. I didn't know what either word meant until I looked them up, something that happens quite often when I'm keying stuff and probably the main reason I can't get my head around parasitic wasps!

Imagine an exterior bract that is sticking straight up against the flowerhead. Now imagine glueing a pen to the outer tip of that exterior bract and then rolling the pen a quarter turn downwards. The bract would now be curved outwards and downwards with a nice even bend. This is arcuate. 

Hamate is the term used for when the front of an individual lobe exhibits a convex curve and the trailing edge of that same lobe has a concave edge. In practice this isn't always as clear cut as it sounds, but it's a distinctive shape all the same. Think of a curved shark fin and you'll be in the right kind of area.

This would be a heck of a lot more professional looking if I had PhotoShop....

So now we can run through the key to Taraxacum sections and, with a fair degree of confidence, say our plant is from section Hamata. This cuts us down from 240 species right the way down to just 19. Now we're making progress! The species in section Hamata are all common and widespread throughout Britain, are found in woodland, grassland, gardens and wasteland and are largely confined to the lowlands below 500 metres. That's what the handbook says anyway. All of that fits in with my plant, so far so good.   

There are nineteen couplets to the section Hamata key. Thankfully our plant drops out pretty quickly. Again I'll highlight the part of the couplet that fits in red.

1) Species lacking an obvious border to the exterior bracts >>2

1) Species with a pale border to the exterior bracts >>12

It's an ugly pic, but it does show the pale border quite well (if you squint)

12) Robust plant, exterior bracts >3.5mm wide (very common species) >>13

12) Mostly medium-sized plant, some exterior bracts <3.5mm wide >>14

13) Distal margin to lobes entire or with teeth, interlobes green, bracts not purplish >> pseudohamatum

13) Distal margin to proximal lobes dentate with large teeth, interlobes smudged blackish, exterior bracts suffused purplish >> lamprophyllum

No black smudging evident on the inter-lobes

No purple colour on the exterior bracts

And now, finally, I've dropped out to species - Taraxacum pseudohamatum. Next I need to read through the species account in the handbook to make sure it all makes sense and then whack it on the Dandelions (Taraxacum) of Britain and Ireland FB Group for confirmation/correction. 

The species accounts give a lot more detail than can be gleaned from the keys. I double-checked various features; outer exterior bract length 10-12mm and shiny green on the underside contrasting with the paler, more pruinose upperside (warning: the text says the upperside of the bracts are often suffused purplish, which is the opposite of what couplet 13 in the key says!)

Detail of outer exterior bracts - upper and undersides

Happy that the ID had been clinched by the extra confirmatory characters mentioned in the species account, I went ahead and posted on the Dandelion FB Group. And waited. Happily, Alex Prendergast, one of the 'tame experts' on that group quickly came back with "Yep, pseudohamatum". I checked the BSBI maps to see its distribution and was genuinely surprised to find that it was entirely 'new' to the Inner Hebrides! Oh cool, I quickly let BSBI Recorder Stephen Bungard know the good news and a short while later the BSBI maps had been updated to this

Green squares denote post-2020 records

Happy days, and I hope it's not just beginner's luck that I started with a nice easy one. 

Music time again. There were a few options for tonight's choice, but seeing as Chris Cornell was one of them the rest quickly dropped away. Here's the great man performing Dandelion live in Chicago 2013. As always, hope you enjoy!