TRIFID BUR-MARIGOLD

Bidens tripartita

Daisy & Dandelion Family [Asteraceae]

month8jul month8july month8aug month8sep month8sept month8oct

status
statusZnative
flower
flower8yellow
inner
inner8brown
morph
morph8actino
petals
petalsZ0
type
typeZclustered
stem
stem8round
stem
stem8fluted

20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
Grows to 75cm high on the dry margins beside fresh water, such as canals, ponds and reservoirs. Growing with Marsh Woundwort (on the left).


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
Branched. Leaves sparsely up the stem. Flowers mainly pointing skywards (unlike Nodding Bur-Marigold which often grows with it)


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
This specimen is suffering a bit of stress with the older leaves turning a deep muddy purple. Leaves toothed, with at least several having 1 to 2 long lateral lobes. Those with one pair of lateral lobes gave rise to the 'Trifid' part of its common name and the tripartita part of its scientific name.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
Leaf teeth variable. The mainly toothless (thay may have a few short soft 'prickles') 'leaves' which are just below and around the flowerhead are bracts, and seem to number between 5 and 8.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
It derives its name from the pair of trifid leaves which occur sporadically about the plant (sometimes not present at all). There are several in this photo, the one near the foot of the imageon the right having unusually deep teeth/lobes.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
Flowerheads angled upwards. Composite, dull yellow, usually all disc-florets (only occasionally does it have some rayed florets). Surrounded by leafy bracts (here 5, can be up to 8) which may have soft fine bristles on the edges.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
This specimen has 8 long leafy bracts surrounding the flower.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
Deep dull-yellow disc florets. Flowers about 15-25mm across.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
The florets are surrounded by two dissimilar rows of phyllaries. Flower stalk ribbed here.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
A mass of leaves, many of which have two long opposite side-lobes. All leaves lanceolate, with coarse teeth.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
The signature tune of Trifid Bur-marigold; the opposite pair of leaves which both have long opposite side-lobes.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
Leaves have winged petioles (stalks).


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
One half of a pair of trifid leaves.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
Many other leaves occur singly.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
The winged leaf which becomes 'groovy' nearer the join.


20th Sept 2016, Leeds & L/pool Canal, Parbold area, Lancs. Photo: © RWD
Opposite pair of leaves with opposite pair of branched stalks.


Not to be semantically confused with : Branched Bur-Reed or Un-branched Bur-Reed nor with Burdocks such as Lesser Burdock (Arctium minus) nor with any of the Burnets such as Great Burnet (Sanguisorba officinalis) nor Bur Chervil (Anthriscus caucalis) or Pirri-pirri-bur (Acaena novae-zelandiae) [plants with similar names from different families]

Easily mis-identified as : other Bur-marigolds.

The version of Trifid Bur-marigold totally lacking trifid leaves is called var. integra and occurs only rarely. London Bur-Marigold (Bidens connata) can sometimes occur with trifid-type leaves, so can be confused with it. To cap it, London Bur-Marigold often grows with Trifid Bur-marigold.

Occasionally Trifid Bur-marigold occurs with ray florets as well as the usual disc florets.

The only way to be sure of the identity of the many species of Bur-marigold is to look at the achenes (which contains a single seed) after flowering; the central ones only - ignoring the outer ones - those of London Bur-Marigold are scarcely flattened (less than twice as wide as thick) and the faces between the four ridges are warty whilst those of Trifid Bur-marigold are strongly flattened (more than twice as wide as thick) with the spaces between the two to four ridges being smooth.

The fruits have two (to 4) barbed bristles at the top by which means it clings to fur and clothing carrying the seed to grow elsewhere. Although many books say that the exact shape of the burs is important in discriminating between other Bur-marigolds, others say that is a highly unreliable witness.


  Bidens tripartita  ⇐ Global Aspect ⇒ Asteraceae  

Distribution
 family8Daisy & Dandelion family8Asteraceae

 BSBI maps
genus8Bidens
Bidens
(Bur-Marigolds)

TRIFID BUR-MARIGOLD

Bidens tripartita

Daisy & Dandelion Family [Asteraceae]