BUTTONWEED

Cotula coronopifolia

Daisy & Dandelion Family [Asteraceae]

month8jul month8july month8aug month8sep month8sept month8oct

status
statusZneophyte
 
flower
flower8yellow
 
morph
morph8actino
 
petals
petalsZ4
 
type
typeZclustered
 
smell
smell8aromatic
aromatic
sex
sexZdioecious
 

10th Oct 2015, Marshside RSPB observatory, Sefton Coast. Photo: © RWD
On the edge of the man-made bird-lake, ready to be trampled by hoards of waders and floaters flocking to meet the bird-spotters with their super-expensive super-long-lensed cameras.


22nd June 2016, Marshside RSPB observatory, Sefton Coast. Photo: © RWD
There is also a patch on a small un-inhabited island with only birds and any amphibians for company for the island is about 50 yards over water from the bird-observation area and in-accessible by mortals. Only a very long zoom lens has any possibility of reaching it. In mid-June they are still quite short and haven't yet reached their ultimate height.


10th Oct 2015, Marshside RSPB observatory, Sefton Coast. Photo: © RWD
It seems at its best after summer is over. Inhabits wettish marshy and usually brackish areas. The land which was once a part of the tidal zone here was reclaimed by sea walls as land, but then in recent decades flooded again to make a bird sanctuary guarded by electric fences all around, presumably to keep the waders in and flower-spotters out. So the waters will be brackish because of salt deposits in the soil.


10th Oct 2015, Marshside RSPB observatory, Sefton Coast. Photo: © RWD
Growing up to 30cm high, it is a short, hairless, fleshy aromatic annual. On these specimens the leaves are mostly linear with auricles, but vary greatly.


22nd June 2013, Lower Test Valley, Hampshire Photo: © Roger & Jacquey Newton
Likes dampish or brackish shallow waters, often near the sea.


22nd June 2013, Lower Test Valley, Hampshire Photo: © Roger & Jacquey Newton
The fawn-coloured shiny stems are succulent, retaining fresh water in case salt water from the sea invades again. Leaves are distinctly shallowly lobed, but varying from broad-linear and undivided to deeply pinnate, even on the same stem.


22nd June 2013, Lower Test Valley, Hampshire Photo: © Roger & Jacquey Newton
Flowers on long stalks. Leaves with auricles wrapped around the stem and often forked into three at the far end.


22nd June 2013, Lower Test Valley, Hampshire Photo: © Roger & Jacquey Newton
 Like Tansy the flowers lack ray florets, and have a cluster of yellow disc florets arranged in a Fibonacci spiral. But most unusually, the florets are four-petalled and the petals curve inwards rather than outwards. The flowers are 8-12mm across and solitary. The flowers are dioecious, with male and female flowers on separate plants. This specimen looks like it is female plant with its central style just visible in those disc-florets which have opened.


22nd June 2013, Lower Test Valley, Hampshire Photo: © Roger & Jacquey Newton
The flowers have several over-lapping green bracts cupping them underneath, a little like those on Trifid Bur-Marigold, another member of the Dandelion & Daisy Family.


22nd June 2013, Lower Test Valley, Hampshire Photo: © Roger & Jacquey Newton
The stems are in sections, splitting into two telescopically, with a sheath around the junction which becomes another shallowly lobed leaf. [grass behind]. Both stems and leaves have a shiny cuticle to retain moisture.


22nd June 2013, Lower Test Valley, Hampshire Photo: © Roger & Jacquey Newton
Flower buds yet to develop stalks and open.


22nd June 2016, Marshside RSPB observatory, Sefton Coast. Photo: © RWD
Just below the bird-observatory there is a patch which has been trampled by hoards of water-birds. Many other plants also grow down here, including Celery-Leaved Buttercup (not in shot).


22nd June 2016, Marshside RSPB observatory, Sefton Coast. Photo: © RWD
Meanwhile the twitchers are wondering why your Author is squeezing himself half-way out of the window and dangling has cheapo cheapo camera as far down passed the electric fence wire as it is possible for him to get without getting electrocuted, pointing his camera directly downwards at the ground 20 feet below. Even at only 20 feet away a long zoom-lens has great difficulty getting any half-decent image of the flower-head.


Not to be semantically confused with : the Genus Colutea [plants belonging to the Bladder-senna Genus (in the Pea family Fabaceae) such as Bladder Senna itself].

Not to be semantically confused with : Coronopus species (Swinecresses) [plants with similar scientific name] which have similar leaves and vaguely similar stem, but the flowers are not on long stalks nor are they like Tansy (Tanacetum vulgare). Nor with Buck's-horn Plantain (Plantago coronopus) which also has similar leaves and similar scientific name.

Not to be semantically confused with : Cottonweed (Achillea maritima) [which has a similar sounding name and belongs to the same Dandelion & Daisy Family (Asteraceae)]

Unlike most other plants belonging to the Dandelion & Daisy Family (Asteraceae) the stems are succulent and 'telescopic', the leaves forked a little like those of Oxford Ragwort, the flowerheads very similar to those of Tansy but the florets have 4 rather than 5 'petals', the sepals behind the flowerhead very similar to those of Corn Marigold, the florets arranged in Fibonacci spirals like those of some Asteraceae and some Brassicaceae (such as Romany Cauliflower).

The disc of florets is not un-like those of the ray-less Tansy (Tanacetum vulgare), but with several important differences. Firstly, the tiny petals number four rather than the usual five. Secondly, those petals do not splay out like those of normal disc florets, but curve inwards.

The plant is salt-tolerant and grows both in damp places and in brackish water, often near the sea but dislikes the shade and any frost. It is a neophyte not native to the UK but to Southern Africa from where it has been introduced to many parts of the world. In the USA it is a problem plant, less so in the UK since it does not yet occupy many hectads. Commonly grown in gardens it is an annual which will re-grow from its own seeds readily.

It can be confused with other Cotula species such as Leptinella (Cotula squalida, but that has Tansy type leaves) and with another 11 species. However the above photos are definitely Buttonweed itself in account of the succulent stems that this specimen possesses, although not every specimen of Buttonweed (as in Cotula coronipifolia) possesses succulent stems. But because this specimen does, it can be no other Cotula species (according to Prof. Clive Stace's key for Cotulas).

Buttonweed is dioecious, with male and female flowers on separate plants, but not all Cotula species are. The sex of the above plant(s) is not known to your Author.

CONSTITUENTS OF BUTTONWEED

The plant is aromatic and contains about 57 components in the essential oil, the most important compound detected in the leaves being the spiro-sesqi-terpenoid Agarospirol at 10.4% , 1-Eicosanol (aka Arachidyl Alcohol, CH3(CH2)38OH) at 17% in the stem and Hexacosane (CH3(CH2)24CH3) at 31% in the flowers. The most abundant oils obtained from the roots were Heptacosane (CH3(CH2)25CH3) (28%), 1-Eicosanol (15%) Octacosane ( (CH3(CH2)26CH3)) (5%) and the terpene 4-Amorphene at 5% which has similarities to the terpenoid Cadinene, all of which are solids at 20°C and probably not volatile so your Author suspects some other more volatile substances are responsible for the aromatic odour.

Agarospirol (aka Ephinesol) was only the second spiro-terpenoid to be found in nature. It is a sesquiterpene alcohol which also occurs in Agarwood, hence its name. It possesses neuroleptic properties affecting the central nervous system. Agarwood was used as a sedative in oriental medicine. It is a spiro-vetivane.




Two new alkaloids have also been found in Buttonweed, one an O-glycosidic compound called Cotuzine but Cotuzine A and Cotuzine B are mentioned as the two in scientific literature (however, your Author can only find the formula for Cotuzine and he does not know if it is really called Cotuzine A or Cotuzine B), which are based on the BenzoAzocine skeleton, and a new polyphenolic substance, Corimen, for which your Author can find no structural formula.



  Cotula coronopifolia  ⇐ Global Aspect ⇒ Asteraceae  

Distribution
 family8Daisy & Dandelion family8Asteraceae

 BSBI maps
genus8Cotula
Cotula
(Buttonweeds)

BUTTONWEED

Cotula coronopifolia

Daisy & Dandelion Family [Asteraceae]