field pennycress (Thlaspi arvense)
Teruncius arvensis (L.) Lunell
Thlaspi baicalense DC.
Thlaspi collinum M.Bieb.
Thlaspi strictum Dalla Torre & Sarnth.
Thlaspidea arvensis (L.) Opiz
CONFIRMATION STATUS: Pending confirmation.
TAXONOMY: The currently accepted scientific name of field penny-
cress is Thlaspi arvense L.. The most distinctive characteristic of field
pennycress is the large size of the coin-shaped seedpods (at least 1/3"
long when mature). Other members of the Mustard Family have seedpods
that are long and slender, or their seedpods are flat and round like field
pennycress, but smaller in size.
NATIVE STATUS: Introduced, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS:
Habit: This adventive winter or summer annual is about 12½' tall, branch-
ing occasionally.Plants that are winter annuals form a rosette of leaves up
to 6" across. These leaves are oblanceolate or obovate and have long petio-
les. Summer annuals and 2nd-year winter annuals develop a central stem
and several side stems. These stems are glabrous, ribbed, and winged along
some of the ribs.
Leaves: The hairless alternate leaves are up to 4" long and 1" across.
They are lanceolate, oblanceolate, or narrowly ovate, and have slightly
wavy margins with a few blunt teeth. The lower leaves have short petio-
les or they are sessile, while the middle to upper leaves clasp the stem. At
the base of each middle or upper leaf, there is a pair of ear-like lobes that
clasp the stem and taper to a blunt point.
Flowers: Both the central stem and upper side stems terminate in erect
racemes of small white flowers. Initially, the flowers bloom near the apex
of a raceme, which later lengthens to about 3-6" as it matures. Each flower
is about 1/8" across when fully open and has 4 white petals and 4 green
sepals. The slender pedicel of each flower is up to ½" long. A few plants
that are summer annuals may bloom later in the year. There is no notice-
able floral scent, although the foliage may have a mustard-garlic aroma.
Fruit/Seeds: Each flower is replaced by a seedpod up to ½" long and a-
cross that is nearly orbicular (a silicle). This seedpod has 2 cells, each
containing several seeds, which are surrounded by a wide membranous
wing. There is a small notch at the top of each seedpod. The seedpods are
held more or less erect relative to the raceme. They eventually become
detached from the raceme, and blow about in the wind. Each dark brown
seed is oval-shaped, but well-rounded on one end and tapering to a point
on the other. Across its surface there are curved concentric ridges that re-
semble the patterns of a fingerprint.
Roots: The root system consists of a taproot. This plant spreads by reseed-
REGENERATION PROCESS: Field pennycress propogates itself by
HABITAT TYPES: Field pennycress is adventive from Eurasia. Habitats
include cropland, fallow fields, areas along roadsides and railroads, gar-
dens and nursery plots, weedy meadows, and waste areas. This plant pre-
fers disturbed areas, and its capacity to invade higher quality natural hab-
itats is low. This is a common agricultural weed.
SITE CHARACTERISTICS: Field pennycress prefers full sun, mesic
levels of moisture, and a fertile loam or clay-loam are typical growing
conditions for this plant.
SEASONAL DEVELOPMENT: The blooming period usually occurs
from late spring to mid-summer, and lasts 1-2 months for a colony of
GENERAL DISRIBUTION: Although the state of Alabama and some
of the Canadian Northwest Territories have yet to report field pennycress,
it is likely this species is found in all states and provinces of the United
States and Canada.
SKY MEADOWS DISTRIBUTION: To be determined.
IMPORTANCE AND USES: The nectar of the flowers attracts primar-
ily small bees and flies. The caterpillars of some white butterflies and
Pyralid moths probably feed on the foliage, including Pieris rapae (cab-
bage white), Pontia protodice (checkered white), Eustixia pupula (Pyralid
moth sp.), and Evergestis pallidata (purple-backed cabbageworm moth).
Mourning doves occasionally eat the seeds of weedy members of the Must-
ard Family. Because the foliage has a bitter-garlic flavor, it is not a prefer-
red food source for mammalian herbivores. When dairy cattle eat this plant,
their milk develops an off-flavor.
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