May 15, 2020

Two Sow-thistles


Especially in somewhat ruderalized surroundings and not far from human activity you can find Sow-thistles. Those big 'Thistles' enjoyed the rain from past weeks to grow really big. The two species here below are easy to find. They look much alike.







Here Prickly Sow-thistle (Sonchus asper) on the side of a small road. (Take 'prickly' with a grain of salt.)






And here Perennial Sow-thistle (Sonchus oleraceus) on the edge of a field. (Also take 'perennial' with a grain of salt, it is mostly annual.) Both species have yellow flowers in open, slightly chaotic, panicles.








Maybe the inflorescences of Prickly Sow-thistle are a bit less dense, and the flowers of a slightly darker yellow...






 
...than those of Perennial Sow-thistle). But the difference is not really big.
For a safe bet, look at the leaves.






Perennial Sow-thistle has deeply incised leaves often glaucous and not shiny. Where the leaf is attached to the stem there is on both sides a pointed auricle.







The leaves of Prickly Sow-thistle are prickly, of course, but they are nothing compared to those of real thistles. They are brilliant on the upper surface, and green with sometimes a tinge of red. There are also auricles, and they are rounded.





And this spring rosette? Difficult to see, notwithstanding its bluish colour it is a Prickly Sow-thistle.