Which Arenaria?

Submitted by Broekhuis on Fri, 05/15/2015 - 19:39

My seed for Arenaria tetraquetra from the 2013/2014 seedex gave me plants with woolly oval leaves. Quite interesting, but not at all like photos of the species that I've found online. It recently started blooming, with flowers much like those of A. grandiflora, so I think the genus might be correct. But which species?

My page about it is here: http://www.robsplants.com/plants/ArenaTetra

A few representative photos:




Submitted by Lori S. on Fri, 05/15/2015 - 21:38

The flower is that of Cerastium rather than Arenaria.  What you've grown is Cerastium alpinum ssp. lanatum, which is a decent plant, if not what was expected.

Here are some photos for comparison:

cerastium alpinum lanatum

Oh, by the way, Rob, I left a note on your website a while back in the Codonopsis bhutanica entry - unfortunately, the plant shown is C. clematidea.  

I only managed to actually get (and germinate) C. bhutanica this year - previous seedex offerings were always C. clematidea!  This time, I got both wild-collected seed from one of the excellent Czech seed collectors and also seedex seed; the seedlings are different from C. clematidea and they also match each other, so I'm happy!

Good for you, Lori, to finally get the correct C. bhutanica.  I finally have the correct C. ovata, thanks to Far Reaches Farm.  I can't tell you how many versions of C. clematidea I received from seed exchanges over the years, masquerading as all sorts of wonderful Codonopsis!

Submitted by Broekhuis on Sat, 05/16/2015 - 10:58

Thanks for the ID. Always good to set things straight. What are the distinguishing features by which you could tell the flower was a cerastium? I'm not great with the finer details of botany :-)

Yeah, I need to fix that codonopsis page. Congrats on getting the real thing - I expect photos of flowers next year!

Yeah, I hope to have flowers, as the final test... if you Google C. bhutanica, you can see that the internet photo record is horribly mixed up, but I'm relying on a few photos that seem to show the real thing.   Well done on C. ovata!

Arenaria has petals that are entire or slightly emarginate (i.e. with a notch at the apex), while Cerastium petals are usually 2-cleft at the apex.  (There are other finer details, predictably... number of styles, etc..)  

If you just do a Google Image search on both the words Arenaria and Cerastium, you can see how this applies, as follows (nothwithstanding that, especially as you scroll further down in the photos, some of these may be mis-ID'd, but you get the gist):