PURPLE LOOSESTRIFE

SPIKED LOOSESTRIFE

Lythrum salicaria

Loosestrife Family [Lythraceae]

month8jun month8june month8jul month8july month8Aug

status
statusZnative
 
flower
flower8purple
 
inner
inner8cream
 
morph
morph8actino
 
petals
petalsZ6
(5 - 7)
type
typeZclustered
 
type
typeZtieredwhorls
 
type
typeZspiked
 
stem
stem8square
 
sex
sexZbisexual
 
sex
sexZheterostylous
 

5th Aug 2007. WWT London wetland Centre. Photo: © Roger Hewitt
Loves to grow near fresh water but not usually in it, but if it is shallow enough near the waters edge it will often have a paddle. Spreads wildly on fens, marshes, less so beside canals and ditches where the opportunity is restricted to a linear path.


2nd Sept 2016, roving bridge, nr Bollington, Macclesfield Canal Photo: © RWD
Some of these tall specimens are probably in the shallow parts of the canal.


1st Aug 2008, In a ditch near Croston, Preston. Photo: © RWD
Making a break for it in an arable field. The ground must be damp there.


20th Sept 2008, Huddersfield Narrow Canal, Uppermill. Photo: © RWD
This woody specimen has, somewhat unexpectedly, multiply-branched spikes of flowers, but it is indeed Purple Loosestrife, albeit, a somewhat older specimen to the others shown here.


2nd Aug 2009, Ex-Windsor High School grounds, Salford, Lancs. Photo: © RWD
Said to grow up to 1.5m high...


2nd Sept 2016, roving bridge, nr Bollington, Macclesfield Canal Photo: © RWD
Probably the tallest Purple Loosestrife your Author has ever seen, growing under the shade of trees and a roving canal bridge (which has a knot topography). This specimen easily surpasses the claimed maximum 1.5m growing height of Purple Loosestrife and must stand about 3 metres or slightly more high. No, its not taller than the roving bridge - don't forget to take perspective into account - the camera is not an infinite distance away...


2nd Sept 2016, roving bridge, nr Bollington, Macclesfield Canal Photo: © RWD
Yet another very tall specimen (again much greater than 1.5m). This shows the opposite leaves alternately at right-angles to each other up the stem to best advantage.


24th July 2013, Moses Gate Country Park, Farnworth, Gtr M/cr. Photo: © RWD
Flower whorls very conspicuous on this plant.


16th Aug 2005, Cold Heindle, Barnsley Canal. Photo: © RWD
Fully developed flower spikes now not so obviously in whorls.


24th June 2006, Worcester & Birmingham Canal. Photo: © RWD
On young specimens where the flowers have not yet fully developed the whorls of flowers are more easily discerned, being well spaced out.


24th June 2006, Worcester & Birmingham Canal. Photo: © RWD
Not yet opened flower buds. The sepal tubes redden under the hot summer sun. Sepal teeth are long. Stems are round to angular (including sometimes square with ribs at the corners), the leaves either in opposite pairs, or in whorls of three.


24th June 2006, Worcester & Birmingham Canal. Photo: © RWD
The stems and leaves have fine short hairs. The top whorl has some flower buds below which are still to open.


16th Aug 2005, Cold Heindle, Barnsley Canal. Photo: © RWD
As the plant matures the flower whorls stretch out and the flower-spike become more uniformly covered in flowers.


24th June 2006, Worcester & Birmingham Canal. Photo: © RWD
The petals normally number 6, but 5 or 7 is also quite common.


29th July 2020, waters meet, Trafford, Bridgewater Canal, Mcr. Photo: © RWD
A green-striped sepal cup showing its shallow teeth and the paper thin crinkled petals. Sticking radially outwards from the V-shaped groove formed in the sepal cup are 5 long, dark-green and thin teeth.

Five of the stamens are grey (above a second set of five stamens which here are cream coloured). [The single stigma in this trimorphic/heterostylous specimen must be below both sets of stamens.]

Lower down are two as-yet un-opened flower buds with a 5 radially-ribbed purple cap (probably the petals, folded up and ready to unfold in a crinkled manner).



29th July 2020, waters meet, Trafford, Bridgewater Canal, Mcr. Photo: © RWD
The 5 very long, thin, dark-green sepals are hairy and a bit sinuous like an octopus's tentacles. The ribbed dark-red cap with central pale, short, fuzzy hairs are the petals. In the two easily visible lower ones there are 6 rather than 5 ribs - so these two will have 6 petals when the red cap opens and unfolds.


29th July 2020, waters meet, Trafford, Bridgewater Canal, Mcr. Photo: © RWD
This flower with 6 petals also has 6 chocolate-brown stamens and 6 cream coloured stamens lower down. The stigma must be below the cream coloured stamens on this specimen.


2nd Aug 2009, Ex-Windsor High School grounds, Salford, Lancs. Photo: © RWD
The flowers are heterostylous, meaning that the flowers occur in two or more types, with their styles and stamens being different lengths in comparison to each other. In the case of Purple Loosestrife, which is Tristylous, there are three basic types of flower to be found, each having two sets of six stamens of differing length and a style of yet another length. One morph has a short style and a set of medium length and a set of long stamens; another morph has a medium length style and sets of both long and short stamens; the third morph has a long style with sets of medium and with short stamens. Pollen transferred from flowers of the same morph will not result in fertilization because the individual morphs are self-incompatible. The three flower morphs are adapted to pollination by different insects. Generally, pollen from the nearest stamens will pollinate the stigma that is closest to it. This plant has a very short single style hiding deep within the sepal tube. Two sets of six anthers are longer than the style, the medium-length set has yellow anthers in the photo, the set with darker anthers here are the longest.


24th July 2013, Moses Gate Country Park, Farnworth, Gtr M/cr. Photo: © RWD
Whereas on this plant the single style (with the green 'discus' termination) is longer than the two shorter sets of six stamens, the shortest set almost hidden within the sepal tube. Your Author does not, at present, have photos of the third kind of heterostyly, where the style is of medium length, intermediate in length between the long set of stamens and the short set of stamens. He is open to any photo submissions.

Note that not all specimens of the flowers are trimorphic; some may be monomorphic with equi-length stamens (but your Author is not sure whether this monomorphic also applies to the style?). Your Author saw some like this and was puzzled until he read that not all are trimorphic (exhibit heterostyly).



2nd Sept 2016, roving bridge, nr Bollington, Macclesfield Canal Photo: © RWD
The flowers with petals above; the sepal cups without their flowers below - some showing a few of their 5 to 7 stamens.


2nd Sept 2016, nr Bollington, Macclesfield Canal Photo: © RWD
Some of the flowers closest to the stem here have their petals folded away in the sepal cup, yet to unfold and open.


22nd Sept 2010, the resr edge, Blackleach, Walkden, Gtr Mcr. Photo: © RWD
The fruits turn reddish in Autumn.


24th July 2013, Moses Gate Country Park, Farnworth, Gtr M/cr. Photo: © RWD
Opposite leaves in quadrature on a square hairy stem, branchlets starting to grow.


24th July 2013, Moses Gate Country Park, Farnworth, Gtr M/cr. Photo: © RWD
Leaves lanceolate, lacking teeth, here in opposite pairs (but can also be in whorls on the same plant).


24th July 2013, Moses Gate Country Park, Farnworth, Gtr M/cr. Photo: © RWD
Stems square in places. Opposite leaves with leafed branches starting to appear above them.


Some similarities to : Some Woundworts, but the flowers are open and six-petalled. Also superficial resemblance to Butterfly-Bush

Distinguishing Feature :

No relation to : Yellow Loosestrife, Dotted Loosestrife, Fringed Loosestrife, Whorled Loosestrife, Tufted Loosestrife or Lake Loosestrife which all belong to the Myrsine Family whereas Purple Loosestrife belongs to the Loosestrife Family. Confusing? Yes. Obtuse too.

The text-books say that the stems are square, but in some of these photographs they look hexagonal in places, and round in others. Maybe the text-books are averaging 'hexagonal' and 'round' to arrive at 'square'? If they were square, then why are the leaves sometimes in triplets, as the text-book says? Does one side in four lose out to a leaf?

From a distance, a drift of Purple loosestrife can be mistaken for Rosebay Willowherb. In some parts of the World, wetland areas of North America and New Zealand for instance, Purple Loosestrife is an invasive species and subject to control measures. Left to its own devices it will readily spread.

The flowers are Heterostylous, with 3 differing permutations of style length in comparison to the two different lengths of two sets of stamens. See the captions for further information. Note that not all specimens of the flowers are trimorphic; some may be monomorphic with equi-length stamens (but your Author is not sure whether this monomorphic also applies to the style?). Your Author saw some like this and was puzzled until he read that not all are trimorphic (that is, exhibit heterostyly).


  Lythrum salicaria  ⇐ Global Aspect ⇒ Lythraceae  

Distribution
family8Loosestrife family8Lythraceae
 BSBI maps
genus8Lythrum
Lythrum

PURPLE LOOSESTRIFE

SPIKED LOOSESTRIFE

Lythrum salicaria

Loosestrife Family [Lythraceae]

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