This plant is a summer annual about ¾-2½' tall that branches
occasionally. The stems are light green, terete, stellate-pubescent,
and spiny. The sharp spines are 4-10 mm. long., yellow, and
straight. Alternate leaves occur along these stems that are 1-3½"
(2.5-9 cm.) long and ¾-3" (2-7.5 cm.) across. These leaves are deeply
pinnatifid with obtuse lobes that sometimes develop smaller secondary
their margins are toothless and very undulate (both horizontally and
vertically). These lobes are irregularly shaped, although they tend to
be obovate or broadly oblong. The upper leaf surface is medium
green and mostly glabrous, except for scattered short hairs, while the
lower leaf surface is pale green and stellate-pubescent. Along the
central vein of the lower leaf surface, there are often scattered
spines that resemble those along the stems.
The petioles are ½-3" long,
mostly pale green, and stellate-pubescent; their upper sides are flat
to slightly concave, while their lower sides are convex. The lower
sides of the petioles also have spines that resemble those along the
Sometimes the lower petioles become pale reddish purple with age. The
upper stems terminate in short racemes of flowers. There are about 3-10
flowers per raceme, although some flowers may abort. Each flower is
about 1" (2.5 cm.) across, consisting of yellow corolla with 5
ovate-triangular lobes, a short-tubular green calyx with 5
linear-lanceolate teeth, 5 stamens, and a pistil with a single style.
Both the body and lobes of the calyx are stellate-pubescent; the
body of the calyx, which encloses the ovary, is also densely covered
with spines that resemble those of the stems and other parts of this
plant. The stamens are dimorphic: 4 upper stamens
(organized as 2 pairs) are yellow, straight, and smaller in size than
the lower stamen, which is more orange-red (particularly toward its
tip) and slightly curved. The pedicels of the flowers are up to ½" (12
blooming period occurs from early summer to early fall, lasting 1½-3
months. In the absence of cross-pollination, the flowers are
self-fertile. After the blooming period, each raceme elongates to
as much as 3" in length, often curving laterally. As the berries
develop, the spiny calyces enclosing them expand in size and become
more or less globoid. These berries are semi-dry and inedible; each
berry contains several seeds. Eventually, the plant breaks off near the
base of it central stem, when it becomes a tumbleweed that can be blown
about by the wind, scattering its seeds along the way. Individual seeds
are 2.0-2.5 mm. long, dark brown or black, and chunky. The root system
consists of a branching taproot that can run deep into the ground. This
plant reproduces only by reseeding itself.
preference is full sun, mesic to dry conditions, and open soil
containing loam, clay, or stony material. Alkaline soil is readily
tolerated. Hot summer weather is preferred. Seeds require exposure to
cold temperatures (winter dormancy) before they will germinate; they
can remain viable in the ground for up to 10 years.
The non-native Buffalo-Bur is occasional in
central and northern
Illinois, while in the southern section of the state it is uncommon or
absent (see Distribution
). It is adventive from areas further to
the west in the United States and Mexico. This plant has also spread to
Eurasia, Australia, and South Africa, where it is regarded as a
troublesome weed in many areas. Habitats consist of dry upland
pastures, roadsides, areas along railroads, construction sites,
and waste areas. This weedy plant is typically found in open disturbed
areas where the ground surface has been exposed and there is reduced
competition from other ground vegetation.
The flowers are cross-pollinated by medium- to large-sized bees,
including bumblebees. The floral reward of such visitors is
pollen. Several species from the leaf beetle family (Chrysomelidae)
feed on the foliage of Buffalo-Bur and other Solanum spp.
(Potato Flea Beetle), Epitrix fuscula
(Eggplant Flea Beetle), Epitrix
(Tobacco Flea Beetle), Lema
(Three-Lined Potato Beetle), and Leptinotarsa decemlineata
(Colorado Potato Beetle). Buffalo-Bur is one the original host plants
of the Colorado Potato Beetle, which expanded its range eastward after
the potato (Solanum
) became widely cultivated. The
(Dock Aphid) also sucks plant juices from
many Solanum spp.
The foliage of Buffalo-Bur contains alkaloids that
are toxic to mammalian herbivores, and its spines can injure the
gastrointestinal tracts and mouthparts of such animals. Therefore, they
usually avoid browsing on this plant, although it is sometimes found in
the fodder (e.g., hay) that is fed to such animals. The spiny fruits of
Buffalo-Bur can cling to the woolly hairs of buffalo and
domestic sheep. As a result, these animals can spread the seeds to new
A construction site in Urbana, Illinois.
Among the Solanum spp.
in Illinois, Bur-Bur can be
distinguished by its large yellow flowers (about 1" or 2.5 cm. across),
bluntly lobed leaves, spiny foliage, and spiny fruits. Because this
western plant prefers areas with a dry climate and relatively barren
soil, it is not invasive in Illinois to any significant extent, however
occasionally scattered plants of this species are encountered. A more
common species within the state, Solanum
also has spiny foliage, but its flowers are either white or pale purple
and its fruits are yellow berries without spines. There are other
western Solanum spp.
in Illinois that are rarely encountered, but they
lack the yellow flowers of Buffalo-Bur and differ from it in other
characteristics. Sometimes Buffalo-Bur has been referred to as Solanum cornutum
but apparently this is the scientific name of another plant species.