Which St John's Wort?

[mikepage]

Could someone tell me which St John's Wort this is. Also, what is the best way to distinguish them for future reference? Many thanks...

[KeenTeen17]

Shape of the flower makes it look like Perforate St Johns Wort to me. This is one of the easier ones to identify because if you take a leaf and look through it at the sun, you should see little translucent holes.

[mikepage]

okay, thank you very much for the info...

[cornish-thyme]

If its not rerforate St John's wort then another possibility could be Square-stalked St John's wort, which has, as the name implies, a square stalk in cross-section (you can feel the 'corners' on the stem).

[KeenTeen17]

Originally Posted by cornish-thyme

If its not rerforate St John's wort then another possibility could be Square-stalked St John's wort, which has, as the name implies, a square stalk in cross-section (you can feel the 'corners' on the stem).

Welcome to WAB CT.

In my experience the flowers of Square Stalked are usually smaller than the ones shown in the photo and the flowerhead is very dense.

[mikepage]

thank you all for the information - it is very useful stuff. I have checked the foliage and it is indeed perforate st john's wort.

[Rambling Rob]

Apologies if this is a bit of ID overkill.

I was photographing this species yesterday afternoon and noticed something which also shows very clearly in your photo - the dark dots which are concentrated around the margins of the petals.

(The leaves of square-stemmed St John's Wort also have the translucent dots, by the way.)

Rob

[leifus]

Originally Posted by Rambling Rob

Apologies if this is a bit of ID overkill.

I was photographing this species yesterday afternoon and noticed something which also shows very clearly in your photo - the dark dots which are concentrated around the margins of the petals.

(The leaves of square-stemmed St John's Wort also have the translucent dots, by the way.)

Rob

so you can tell square-stalked sjw and perforate sjw apart by...

the shape of the stem
and the dark dots?

[Rambling Rob]

Hi Leifus,

I don't know about stem shape as a defining characteristic - some other spp. have squarish stems too - but certainly H. perforatum has the translucent dots on the leaves and the black dots concentrated at the margins of the petals. Here's a crop from a photo taken a couple of days ago:



Just to make things more confusing there is an imperforate St John's Wort H. maculatum which has square stems, no or few translucent dots in the leaves, and also has spots on the petals but the spots are distributed across the petal surface rather than at the margins. Looks like a telling feature between this one and square-stemmed SJW is that the square stems of square-stemmed SJW are also winged.

I'm no expert, by the way, just been reading up about it in a couple of floras,
Rob

[cornish-thyme]

its no good, i've got to ask for confirmation of the id of the plants growing in my meadow now ..i'm fairly sure this is square stalked St Johns Wort. It has a square stalk and no visible spots on the petals, without going out and finding one of the plants (and its belting down with rain at the moment) i can't say whether it had any tranlusent dots on the leaves. i was pretty confident that i'd got the right id, but as always the more i read the more worried i get
Thanks in advance and sorry if i'm being an idiot