PRICKLY LETTUCE

COMPASS PLANT

Lactuca serriola

Daisy & Dandelion Family [Asteraceae]

Flowers:
month8jul month8july month8aug month8sep month8sept

Pappus: pappusZpossible (white, compound)
pappus8aug pappus8sep pappus8sept pappus8oct

status
statusZarchaeophyte
 
flower
flower8yellow
 
morph
morph8actino
 
petals
petalsZMany
 
stem
stem8round
 
stem
stem8milkysap stem8milkylatex
 
stem
stem8ribbed
 
smell
smell8slight smell8slightly
slight
toxicity
toxicityZmedium
 

1st Sept 2012, nr. Salford Crescent Rly Stn, Gtr Mcr. Photo: © RWD
A tall plant, up to 2m high, but not as sturdy as Great Lettuce.


13th Aug 2011, a garden, Manchester Rd, Bolton, Lancs. Photo: © RWD
Is highly branched, branches curving skywards, with most of the flowers being near the top one-third.


23rd July 2012, Crescent PH, Salford. Photo: © RWD
Mid-part of plant. Branches alternate with single dark-greyish-green leaf with auricles immediately below the branches.


1st Sept 2012, nr. Salford Crescent Rly Stn, Gtr Mcr. Photo: © RWD
Leaves are greyish green and alternate up main stem.


31st July 2011, a garden, Manchester Rd, Bolton, Lancs. Photo: © RWD
The leaves wrap around the main stem where they join. Just above each leaf a branch emerges that mostly follows just above the leaf, curving upwards.


1st Sept 2012, nr. Salford Crescent Rly Stn, Gtr Mcr. Photo: © RWD
The leaves have pointed auricles that clasp each side of the main stem. The main stem is whirish, with perhaps just a hint of redness about. The leaves have weak and shortish spines along the edges, and a prominent whiteish mid-rib.


The Crescent PH, Salford, Lancs. Photo: © RWD
The flowers are small, about 11-13mm across and pale yellow.


13th Aug 2011, a garden, Manchester Rd, Bolton, Lancs. Photo: © RWD
Branch stems zig-zag slightly at each minor branch.


1st Sept 2012, nr. Salford Crescent Rly Stn, Gtr Mcr. Photo: © RWD
The flowers are in loose clusters and only open to about 110° subtended angle.


23rd July 2012, Crescent PH, Salford. Photo: © RWD
A young plant, buds and leaves (here wrapped around the stems) are still developing.


1st Sept 2012, nr. Salford Crescent Rly Stn, Gtr Mcr. Photo: © RWD
The flower buds have a slight bulge at the bottom (but not as much as do Sow-thistles) and taper towards the top. The flowers have overlapping narrow bracts of differing lengths like those of Smooth Cat's-Ear which are often purleish at their tips.


13th Aug 2011, a garden, Manchester Rd, Bolton, Lancs. Photo: © RWD
The flowers have a tendency to be tinged red-purple, especially on the outer/under sides. Bracts also tinged reddish-purple.


16th Aug 2012, The Crescent PH, Salford, Lancs. Photo: © RWD
Like Nipplewort, the flowers are small and have less than 20 ray florets and perhaps fewer disc florets in the middle, both similarly coloured.


16th Aug 2012, The Crescent PH, Salford, Lancs. Photo: © RWD
Pappus trying to break out on the right.


16th Aug 2012, The Crescent PH, Salford, Lancs. Photo: © RWD
There are correspondingly few (compared to Dandelion) parachutes, which have simple un-branched hairs fanning out into a cone.


16th Aug 2012, The Crescent PH, Salford, Lancs. Photo: © RWD
The seeds are huge in comparison to the parachute (larger than those of Dandelion), and Teak-brown in colour.


22th Aug 2012, The Crescent PH, Salford, Lancs. Photo: © RWD
The lower leaves on the main stem are alternate, and often have a twist and often pointing vaguely upwards.


18th Aug 2012, The Crescent PH, Salford, Lancs. Photo: © RWD
When the sun emerges the leaves try to follow it, which accounts for their contortions. Leaves are mostly un-lobed, but some, especially the lowest, have deep lobes almost to the mid-rib (not shown).


1st Sept 2012, nr. Salford Crescent Rly Stn, Gtr Mcr. Photo: © RWD
Un-like Great Lettuce, the stems are whitish (with perhaps just a hint of redness) and lack spines. The leaves are grey-green and have a faint but coarse whitish net-veins.


1st Sept 2012, nr. Salford Crescent Rly Stn, Gtr Mcr. Photo: © RWD
The spines are much longer and sharper on the underside of the mid-rib of the leaf than they are on the edge of the leaf. Hence the name Prickly Lettuce.


Could be mistaken for : a bolted example of Garden Lettuce but that is shorter at 75cm and neither (slightly) foetid nor prickly, with un-lobed and un-toothed leaves.

Some similarities to : Great Lettuce but that is both taller and stouter, has prickles on the stems, and the stems are tinged purple. Both have prickles on the mid-rib of the underside of the leaf and ooze a milky sap.

Uniquely identifiable characteristics

Distinguishing Feature : Perhaps the spines on the underside of the leaf along the mid-rib. The greyish-green leaves and whitish main stem.

No relation to : Prickly Poppy, Prickly Heath or Prickly Saltwort, [plants with similar names].

The stems and flowers are tacky to touch leaving the fingers sticky. Broken stems ooze a toxic white latex consisting of sesquiterpene lactones, just like the broken stems of Great Lettuce. It is a casual urban weed, preferring to grow between pavings and in the nook between wall and paving where there is no trampling and little competition from other plants. Also in recently disturbed ground.

In strong sunshine the upper leaves twist around to hold their edges upright in a north-south direction in an effort to avoid the worst of the midday sun, a phototropic response, hence the alternative name of Compass Plant. This is unusual in England but can happen during hot years in southern counties such as Sussex. Mainly a southern UK plant, but mostly avoiding Wales apart from near the coastline.

It smells slightly foetid.


  Lactuca serriola  ⇐ Global Aspect ⇒ Asteraceae  

Distribution
 family8Daisy & Dandelion family8Asteraceae

 BSBI maps
genus8Lactuca
Lactuca
(Lettuces)

PRICKLY LETTUCE

COMPASS PLANT

Lactuca serriola

Daisy & Dandelion Family [Asteraceae]