PELLITORY-OF-THE-WALL

Parietaria judaica

Nettle Family [Urticaceae]  

month8May month8jun month8june month8jul month8july month8Aug month8sep month8sept month8Oct

status
statusZnative
flower
flower8green
inner
inner8red
petals
petalsZ4
stem
stem8round
stem
stem8angular
sex
sexZbisexual
sex
sexZfemale

23rd March 2016, dog hole cave, Cresswell Crags, Derbyshire. Photo: © RWD
Half inside a limestone cave, it spreads by long runners.


23rd March 2016, dog hole cave, Cresswell Crags, Derbyshire. Photo: © RWD
Leaf-clusters before flowering. Leaves have a large variety of sizes.


17th Aug 2007, Whatstandwell, Cromford & High Peak Railway. Photo: © RWD
It takes root in cracks in walls.


17th Aug 2007, Whatstandwell, Cromford & High Peak Railway. Photo: © RWD
Spreading across the surface about a foot across, and perhaps up to 8 inches high.


17th Aug 2007, Whatstandwell, Cromford & High Peak Railway. Photo: © RWD
The leaves are lanceolate, shiny, with prominent veins.


17th Aug 2007, Whatstandwell, Cromford & High Peak Railway. Photo: © RWD
Clusters of tiny red male flowers grow in the leaf axils.


17th Aug 2007, Whatstandwell, Cromford & High Peak Railway. Photo: © RWD
The leaves are alternate along the stem. Female flowers are at the tops of branches, you may just discern the style with a pink 'brush-like' tip protruding from two flowers near the tip of the branch.


16th June 2010, a wall, Colwyn Bay, N. Wales Photo: © RWD
Supporting the 'female flowers grow near the tip of a stalk' hypothesis of one source, these are the brush-like stigmas of female flowers.


16th June 2010, a wall, Colwyn Bay, N. Wales Photo: © RWD
The furry stigmas of female flowers.


11th Aug 2015, a wall, Burscough Bridge, Lancs. Photo: © RWD
Leaves hairy, alternate and without teeth (entire). There are two sets of tiny flowers, those at the summit which are female, and those in small bunches (from 3 to n) at the leaf-axils which are bisexual (hermaphroditic).


2nd Aug 2013, Hilbre Island, Wirral, Merseyside. Photo: © RWD
Hairy red petals. Leaves have long hairs which emerge from tiny bumps like those of Bugloss. Stem angular in places.


17th Aug 2007, Whatstandwell, Cromford & High Peak Railway. Photo: © RWD
The sepals of bisexual flowers become tubular in fruit, so these must be the bisexual flowers in fruit. Every part is covered in short white hairs.


10th Sept 2015, a wall, Hilbre Island, The Wirral. Photo: © RWD


2nd Aug 2013, a wall, Hilbre Island, The Wirral. Photo: © RWD
There are two types of flowers on Pellitory of the Wall plants: female and bisexual (hermaphrodite), because these have doubled creamy-white anthers these must be bisexual flowers. Male parts consist of 4 cream-coloured splayed-out stamens with doubled anthers at the tips..


10th Sept 2015, a wall, Hilbre Island, The Wirral. Photo: © RWD
Here the anthers have opened up to look like white petals and are now devoid of pollen. One of them is missing, presumed flung sling-shot as the stamens spring suddenly outwards from the confines of the four red tepals (now behind and shorter than the stamens).


10th Sept 2015, a wall, Hilbre Island, The Wirral. Photo: © RWD
One of the double-anthers, devoid of pollen. The anther itself is 'fibulated' (ribbed like a rack in a rack and pinnion cog). The fruit here may be sterile?


11th Aug 2015, a wall, Burscough Bridge, Lancs. Photo: © RWD
Bisexual flowers in leaf axil: Four red sepals behind 4 ribbed flattened re-curved stamens (the anthers have dropped off - possibly flung off as the anthers spring back suddenly). If flowers in leaf-axils are supposed to be bisexual flowers (Stace), then the stigmas are missing. If they are male only flowers then there are only stamens, no stigmas and the visible green fruit is sterile - problem solved!


11th Aug 2015, a wall, Burscough Bridge, Lancs. Photo: © RWD
The stamens are highly elastic and spring back when the flower opens, throwing the pollen out, of which there is reportedly a lot. The pollen is also highly allergenic to some folk.


10th Sept 2015, a wall, Hilbre Island, The Wirral. Photo: © RWD
A fertilised fruit will develop beneath this central red style, stigma now spent and brown. Not the bracts are covered in transparent and hooked 'white' hairs for some reason, presumably to cling to animals clothing and carry off a ripened fruit within to grown elsewhere.


10th Sept 2015, a wall, Hilbre Island, The Wirral. Photo: © RWD
One of the bisexual flowers, with both male and female parts?


23rd March 2016, dog hole cave, Cresswell Crags, Derbyshire. Photo: © RWD
Vein-pattern of leaves


Some similarities to : Water Peppers.

Related to: Mind Your Own Business (Soleirolia soleirollii) and to Stinging Nettle (Urtica dioica).

Minute female flowers grow at the tips of the stems, whereas the male flowers grow in clusters within the leaf axils (as one book says) whilst another book (Stace) says that both female and bisexual (hermaphrodite) flowers grow on one plant. But yet another book claims that the flowers are female towards the centre surrounded by either bisexual or male flowers (Readers Digest). You pays your money and takes your choice...

The pollen of Pellitory of the Wall contains a dodecapeptide which accommodates the strangely-named dominant epitopes par o 1 and Par j 1, which are very potent allergens and which can cause a severe allergic reaction in some people. They have chemical structures far too long and complicated to be drawn here.

The hairs of the flowers are sticky but do not, like those of the related Stinging Nettle, sting.

There also exists a very much rarer but introduced and naturalised alien: Eastern Pellitory-of-the-Wall (Parietaria officinalis) which is more robust and usually longer. In the UK this species occurs only in two places.

It grows on old town walls, at the foot of walls, rocks, rubble, or on churches and castles almost throughout the UK. Also on hedge-banks and is a deciduous herbaceous perennial. It is equiped with tiny hooked hairs which hook on to animals fur to be transported elsewhere. It spreads by blown or carried seed.

No types of the three differing flower forms possess petals; but the red calyx can take three different forms: flat, bell-shaped, or tubular hairy and erect.

The sexual composition of the flowers is very complicated, with three types of flowers on the plant and are mostly proterogynous, with the pistil (the four female parts of the flower - ovule, ovary, style and stigma - which is shaped like a wine bottle in the centre of the flower) maturing before the stamen. When the flowers are proterogynous they can take on three forms: bisexual, male only and female only.

Another source claims that the Fertile flowers are are one of four types: Hermaphrodite and functionally male and female; Hermaphrodite but functionally male; or Hermaphrodite but functionally male. Unisexual flowers are also present, either male, or female. Which together make for five types of flower.

In some sexual forms, the stamens only develop after the stigma has protruded from the calyx. Only after the style has dropped off do the anthers un-furl from their confines explosively, scattering their extensive quantities of pollen about, too late to pollinate its own style. The flowers are anemophilous: scattering their pollen on the wind.

The male flowers are like those of Stinging Nettle to which it is related. The female flowers have a 4-lobed and brush-like stigma. The fruits are small and when ripe either fall to the ground or are whisked away by the wind.


  Parietaria judaica  ⇐ Global Aspect ⇒ Urticaceae  

Distribution
family8Nettle family8Urticacaea

 BSBI maps
genus8Parietaria
Parietaria
(Pellitories-of-the-Wall)

PELLITORY-OF-THE-WALL

Parietaria judaica

Nettle Family [Urticaceae]  

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