FIELD PENNY-CRESS

Thlaspi arvense

Cabbage Family [Brassicaceae]

month8apr month8april month8may month8jun month8june month8jul month8july month8aug month8sep month8sept

status
statusZarchaeophyte
 
flower
flower8white
 
inner
inner8yellow
 
morph
morph8actino
 
morph
morph8hemizygo
 
petals
petalsZ4
 
type
typeZspiked
 
stem
stem8round
 
smell
smell8foetid
foetid

9th July 2014, Hampshire Photo: © Simon Melville
A stout and hairless annual which grows up to 60cm high. The species lacks a basal rosette of leaves.


9th July 2014, Hampshire Photo: © Simon Melville
The flowers open and ripen to fruits from the bottom upwards. Fruits flattened and almost circular with an abrupt notch at the apex which reaches the boundary of the oval seed-capsule within. The seed capsule is wider nearer the top and slightly angular at the bottom. The fruit thus has a circumferential wing which is greater than 1mm wide half-way up and is widest at the top. The tiny discoidal style nestles at the bottom of this notch and is very much shorter than the notch is deep.


Photo: © RWD
Stem leaves are clasp the stem and have auricles either side of the stem, which is angular or ridged. The leaves are bluntly toothed.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
The flowers have 4 cupped sepals. As-yet unopened flower buds at the top.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
The flowers have 4 equal-length white petals and 6 stamens in an oval shape surrounding a flat developing fruit.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
Unlike the similar but rarer Shepherd's Cress the flower petals are of equal length, if not quite actinomorphic symmetrical, but rather slightly zygomorphic (hemi-zygomorphic) because of the developing discoidal fruit between opposite pairs, but this is true for a few similar flowers belonging to the Cabbage Family Brassicaceae.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
The style and stigma atop the brown discoidal fruit is quite short. Petals 2.7 to 5mm long.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
The fruit develops in two halves, each half containing between 3 to 8 seeds.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
Style with discoidal stigma nestling between the two halves of the fruit.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
The 6 stamens with anthers. The flower is cupped by 4 green sepals with a thinner whitish 'flash' around the top half.


27th June 2005, Rochdale Canal, Lancs. Photo: © RWD
Tallest when in fruit, up to 50cm high.


27th June 2005, Rochdale Canal, Lancs. Photo: © RWD


27th June 2005, Rochdale Canal, Lancs. Photo: © RWD
No flowers left, all turned to fruit. Fruit 9 to 20mm across when ripe and with a deep cleft at the extremity, with the style much shorter than the tips of the ripened fruit.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
Leaves broadly strap-shaped slightly toothed and clasping the stem with long pointed auricles either side.


24th May 2016, arable fields, Aughton, Ormskirk, Lancs. Photo: © RWD
Stem angular/ribbed. The bluntish leaf teeth.


Not to be semantically confused with : Pennywort (Floating) (Hydrocotyle ranunculoides), Pennywort (Marsh) (Hydrocotyle vulgaris), Hairy Pennywort (Hydrocotyle moschata), New Zealand Pennywort (Hydrocotyle novae-zeelandiae), Wall Pennywort (Umbilicus rupestris) [plants with similar names from the same or differing families]

Easily mis-identified as : Alpine Penny-cress (Noccaea caerulescens), Garlic Penny-cress (), Perfoliate Penny-cress (Microthlaspi perfoliatum), Caucasian Penny-cress (Pachyphragma macrophyllum)and Garlic Penny-cress (Thlaspi alliaceum)

It has a strong foetid odour and sometimes an almost imperceptibly faint garlic smell as well, whereas Garlic Penny-cress (Thlaspi alliaceum) smells distinctly of garlic when crushed. It lacks a basal rosette. An abundant weed of arable fields, but it also grows in waste ground, verges and as a garden weed. The fruits are flat and almost penny-shaped, hence the common name (the penny, of course, being the old 1d penny).


  Thlaspi arvense  ⇐ Global Aspect ⇒ Brassicaceae  

Distribution
 family8Cabbage family8Brassicaceae

 BSBI maps
genus8Thlaspi
Thlaspi
(Penny-Cresses)

FIELD PENNY-CRESS

Thlaspi arvense

Cabbage Family [Brassicaceae]