SQUARE-STALKED ST JOHN'S-WORT

Hypericum tetrapterum

St John's-wort Family [Hypericaceae]

month8jul month8july month8aug month8sep month8sept

status
statusZnative
 		 flower
flower8yellow
 		 inner
inner8orange
 		 morph
morph8actino
 		 petals
petalsZ5
 		 stem
stem8square
 		 stem
stem8winged
(4)		 toxicity
toxicityZlowish
 		 sex
sexZbisexual
 

28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD
An erect plant growing to 60cm high.


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD
Square-stalked St John's-wort looks a lot like Imperforate St John's-Wort apart from the stems which are square and with a wing running down each corner.


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD
Another difference between Imperforate St John's-Wort is that Square-stalked St John's-wort has tiny translucent dots on the leaves (best seen when you hold a leaf up to the light to see the tiny illuminated dots).


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD
The leaves have black glands on the edges and translucent dots on the surface. Sometimes there are also black glands on the petals and sepals.


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD
A third difference between Imperforate St John's-Wort are the narrow and pointed sepals on Square-stalked St John's-wort (the sepals are blunt on Imperforate St John's-Wort). This specimen has a red developing fruit at the top where once the flower was.

The 4 wings on all 4 corners are between 0.25 and 0.5mm wide.



28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD
The flowers, which are a small 9mm to 13mm across, are also a paler yellow on Square-stalked St John's-wort than on Imperforate St John's-Wort). The red object is a developing fruit.


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD


28th Aug 2017, dark peak moors, Baslow area, Peak Dist. Photo: © RWD
Unlucky obtaining un-obscured photos of it, your Author picked the top of a specimen and held it near a rock to keep the wind from flapping it around. The 4-sided and 4-winged stems can be discerned.






AN ANOMALOUS SQUARE-STALKED ST JOHN'S-WORT

1st Sept 2017, a muddy gully, deepest Cheshire. Photo: © RWD
Because of the very small size of the flowers (just 11mm across) and the apparent narrowness of them and their misalignment with the sepals underneath, your Author thought this to be one of the smaller flowered St John's-worts, but he was mistaken. Apparently, because it is late in the season for it, it has taken on slightly differing characteristics, such as those just described. However, compared to the above set of photos from Derbyshire, these are only 3 days later on in the season. Both are in the same year (2017) if about 70 miles apart. Your Author thinks the reason may be that these specimens, in the bottom of a 5 foot-deep muddy ravine, are also possibly starved of light.


1st Sept 2017, a muddy gully, deepest Cheshire. Photo: © RWD


1st Sept 2017, a muddy gully, deepest Cheshire. Photo: © RWD


1st Sept 2017, a muddy gully, deepest Cheshire. Photo: © RWD


1st Sept 2017, a muddy gully, deepest Cheshire. Photo: © RWD

Easily confused with : Square-stalked Willowherb (Epilobium tetragonum), Square-Stemmed Vetch (Vicia monantha) and Square-stemmed Bamboo (Chimonobambusa quadrangularis) [plants with similar names belonging to differing families]

Hybridizes with : Wavy St John's-wort (Hypericum undulatum)

  • to produce (Hypericum undulatum × tetrapterum) to produce × which was found in Cornwall in 2006, and has the same red-tinged sepals, leaves which slightly undulate and narrow ( <0.25mm) wings and either no or only one black glands on each sepal. The flowers are smaller than the 12 to 20mm across of Wavy St John's-wort.

It occurs frequently throughout Britain apart from the extreme North of Scotland. It grows in damp meadows, riverbanks, marshes and here in muddy ditches.

  Hypericum tetrapterum  ⇐ Global Aspect ⇒ Hypericaceae  

Distribution
family8St John's-wort family8Hypericaceae
 BSBI maps
genus8Hypericum
Hypericum
(St John's-Wort)

SQUARE-STALKED ST JOHN'S-WORT

Hypericum tetrapterum

St John's-wort Family [Hypericaceae]