prickly lettuce (Lactuca serriola)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

COMMON NAMES:
prickly lettuce
lettuce
wild lettuce
China lettuce

 

SCIENTIFIC SYNONYMS:
Lactuca altaica Fisch. & C. A. Mey.
Lactuca augustana All.
Lactuca coriacea Sch.Bip.
Lactuca dubia Jord.
Lactuca scariola L.
Lactuca sylvestris Lam.
Lactuca tephrocarpa K.Koch

 

CONFIRMATION STATUS: Pending confirmation.

 

TAXONOMY: The currently accepted scientific name of prickly lettuce
is Lactuca serriola L. This is one of the more common Lactuca spp. (wild
lettuce). The prickles on the leaves are somewhat soft and incapable of
tearing flesh and clothing. However, the bruised foliage emits a rank odor.
Another common name for this plant is wild opium because the latex con-

tains compounds that are mildly sedating and analgesic. Species of wild
lettuce fall into one of two large groups: Those with yellow flowerheads
versus those with light blue flowerheads. Prickly lettuce belongs to the
former group. Prickly lettuce differs from Lactuca canadensis (wild let-

tuce) by its blue-green foliage and the prickles on the undersides of its
leaves. It shares these characteristics with Lactuca saligna (willow lettuce),
but this latter species is smaller in size (3' tall or less), has flowerheads

with about 10 ray florets, and has beaks that are about twice the length of

the achenes. Lactuca floridana (woodland lettuce) has light blue flowers,

quit distinct for Lactuca serriola.

 

NATIVE STATUS: Introduced, United States and Canada.

 

GENERAL BOTANICAL CHARACTERISTICS:

 

Habit: This adventive annual or biennial plant is 2-7' tall and unbranched,

except where the upper flowering stems occur. The central stem is light

green or dull white, glabrous, and round in circumference. There may be

a few prickles toward its base.

 

Leaves: The alternate leaves are up to 12" long and 4" across, becoming

smaller as they ascend the stems. They are blue- green, glabrous, and pin-

nately lobed with a few teeth (however, var. integrata has leaves without

lobes). The lobes have a tendency to curve backwards toward the central

stem and their tips are pointed. Each leaf has short prickles along its mar-

gin and the underside of the central vein. The base of each leaf has a pair

of angular lobes that clasp the stem. Both the stems and leaves contain a

white milky latex.

 

Flowers: Panicles of pale yellow flowerheads are produced from the cen-

tral stem and upper side stems. These panicles are rather long and spread-

ing; they have alternate leaves that are widely spaced and greatly reduced

in size. Each flowerhead is about 1/3" across and about 1/2" in length. It

consists of about 20 pale yellow ray florets and several blue-green bracts

underneath. The ray florets have truncated tips with 5 small teeth, while

the overlapping floral bracts are slender and hairless.

 

Fruit/Seeds: Each floret produces an achene with a thread-like beak that

terminates in a small tuft of white hair. This beak is white and about the

same length as the achene, or slightly longer. The achene is grey or light

brown, oblong with tapering tips, and somewhat flattened with 3-5 fine

nerves on each side. There may be a few teeth near its apex. Distribution

of these achenes is by the wind.

 

Roots: The root system consists of a taproot that is stout and deep.

 

REGENERATION PROCESS: This plant spreads by reseeding itself.

 

HABITAT TYPES: Habitats include abandoned fields, fence rows, areas

along railroads and roadsides, vacant lots, dumps, and miscellaneous
waste areas. This plant prefers highly disturbed areas and doesn't invade
high quality natural areas to any significant degree (this may be less ac-

curate in the more open prairie regions of the western and Great Plains

states).

 

SITE CHARACTERISTICS: Typical growing conditions are full sun
and a mesic to dry soil that can be fertile or somewhat barren. The size
of this plant is highly variable depending on moisture levels and soil
fertility. Sometimes powdery mildew attacks the leaves.

 

SEASONAL DEVELOPMENT: The blooming period can occur from
mid-summer to fall; an individual plant will remain in bloom for about
a month.

 

GENERAL DISTRIBUTION: Prickly lettuce has been identified as
growing in all states in the United States and all the southern Canadian
provinces.

 

SKY MEADOWS DISTRIBUTION: To be determined.

 

IMPORTANCE AND USES: The nectar and pollen of the flowerheads
attract various kinds of bees. The caterpillars of a few species of moths
eat the foliage, including Cucullia intermedia (intermediate cucullia). The
foliage is bitter-tasting and not a preferred food source for mammalian
herbivores, although cattle and white-tailed deer occasionally eat it.

 

 

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