Sonchus canariensis or is it?.

Example Yellow Composite plants on visit to Tenerife. 10th March- 15th March 2019

Tenerife has been isolated from Africa and Europe for 12 million years, so plants have developed many endemic species through geographical separation and adaptation to an extreme environment.

The yellow composites ( Dandelion type) have some really extreme examples that showed up on our first walk from Erjos in the north western region of Teno. The one photographed here was Sonchus canariensis, sometimes called the Tree Dandelion.

Sonchus canariensis?.

To see a 'dandelion' six feet high was a bit of a shock as I had no idea a plant like this existed. Using the 'Natural History of Tenerife by Philip & Myrtle Ashmole' I managed to identify it as Sonchus canariensis. A heavily branched shrub it can reach 3m high, almost a small tree. It was quite common around the Teno region and common around our base in Santiago Del Teide.

Thin Leaf shape, more air than leaf.

Typical leaf shown above but some leaves have a thicker shape, see lower leaves in photo below.
.

Typical Plant with thicker leaves

Very pale yellow-green stem and bracts becoming darker towards tips.

Some variation with more rounded outer bracts, darker type.

Flowers showed some variation in shape of outer bracts and density of inner bracts. Second example has white fluff around the bracts and there are more rounded in shape compared with the first photos.
Quite a difference between these two photos that I can't explain. The number of inner bracts seems much higher in the second type. This looks like more than variation?

Buds before flower opens, similar to type above, darker type.

Post flower , pale type

Stems branch many time to support flowers ( pale type)

Another possible difference is that the pale bracts type seemed to have thiner leaves whereas the darker type bract plants had thicker leaves.

Flower, top view

Receptacle with achenes.

Conclusion. This is quite an amazing plant(s). We were lucky that it was in full flower on our visit but I now wish I had noticed the differences and investigated more at the time. Although the 'Natural History of Tenerife' is an excellent book as it says in its preface it is not a systematic treatment of the plants which will have to wait for another book. I could not find a guide to the plants of Tenerife and have relied on the internet, which has its limitations. I had assumed all these photos are of Sonchus canariensis. The other possibility is that these tree Sonchus have spilt into several species and one name that has come up on the internet is Sonchus arboreus which is not mentioned in the 'Natural History of Tenerife' at all . Sonchus arboreus would appear to be present on Tenerife but I could not find detailed descriptions that would help with these species.

The lack of a good field guide is a major limiting factor when looking at flowers on Tenerife especially when there are so many endemic species (700 ). Photos of both species are present on Google but how reliable they are is hard to say, except they look very similar. None have the detail to really help. Some where there must be detailed descriptions of Sonchus but I have not found it.

The plants photographed were beside the path near the pools just south west of Erjos, so shared the same habitat.
Any comments welcome.

Peter Leonard
Rampton
26th March 2019

Post Script.
The problem to identify Woody Sonchus on the Canary Islands has just got a lot more complex.
I found that some research based on plants grown in a greenhouse in California from seeds obtained in Macaronesia ( Azores, Maderia, Canaries and Cape Verdes) which lists rather more species than the two mentioned above. No ID information is included in the paper and the writers may never have been to to the Canaries. It would appear that the evolution of these Woody Sonchus species has had a lot of scientific attention with papers in Linnean Soc Vol 76:249-285 in 1978 that I can't access.
The paper below contains this list of species, all but two are endemic to the Canaries.
It is mainly about evolution of different leaf shapes in response to habitats.

The California paper can be found at : research gate.net