Cockle Burrs

Cockle Burrs


Huernia pillansii (Cocklebur)

Huernia pillansii (Cocklebur) is a succulent with soft, erect or ascending stems, subglobose when young, becoming narrowly ovate or…

Cockleburs are coarse, herbaceous annual plants growing to 20–47 inches (51–119 cm) tall. The leaves are spirally arranged, with deeply toothed margins. Some species, notably Xanthium spinosum, are also very thorny with long, slender spines at the leaf bases. [5]

The flower heads are of two types One, in short terminal branches, produces only pollen. The other, in clusters in the axils of the leaves, produces seed. [5]

Unlike many other members of the family Asteraceae, whose seeds are airborne with a plume of silky hairs resembling miniature parachutes, cocklebur seeds are produced in a hard, spiny, globose or oval double-chambered, single-seeded bur 0.32–0.79 inches (0.81–2.01 cm) long. It is covered with stiff, hooked spines, which stick to fur and clothing and can be quite difficult to detach. These burs are carried long distances from the parent plant during seed dispersal by help of animals (zoochorous). [6]

Cockleburs are short-day plants, meaning they only initiate flowering when the days are getting shorter in the late summer and fall, typically from July to October in the Northern Hemisphere. They can also flower in the tropics where the daylength is constant. [ citation needed ]

Over 200 names have been proposed for species, subspecies, and varieties within the genus. Most of these are regarded as synonyms of highly variable species. Some recognize as few as two or three species in the genus. The Global Compositae Checklist recognizes the following

  • Xanthium artemisioides – Ambrosia arborescens
  • Xanthium fruticosum – Ambrosia arborescens

The cocklebur is legally listed as a noxious weed in the states of Arkansas and Iowa in the United States of America. [ citation needed ]

The common cocklebur (Xanthium strumarium) is a native of North America. It has become an invasive species worldwide. It invades agricultural lands and can be poisonous to livestock, including horses, cattle, and sheep. Some domestic animals will avoid consuming the plant if other forage is present, but less discriminating animals, such as pigs, will consume the plants and then sicken and die. The seedlings and seeds are the most toxic parts of the plants. Symptoms usually occur within a few hours, producing unsteadiness and weakness, depression, nausea and vomiting, twisting of the neck muscles, rapid and weak pulse, difficulty breathing, and eventually death. [ citation needed ]

The plant also has been used for making yellow dye, hence the name of the genus (Greek xanthos = 'yellow'). The many species of this plant, which can be found in many areas, may actually be varieties of two or three species. The seed oil is edible. [ citation needed ]

Xanthium strumarium is known as cang er zi (苍耳子) in traditional Chinese medicine. Xanthium is also used to treat nasal and sinus congestion. [7]

The spines and seeds of this fruit are rich in a chemical called carboxyatractyloside (CAT), formerly referred to as xanthostrumarin, which is the chemical that is responsible for most of the adverse effects from the use of cang er zi. CAT has been shown to be a growth inhibitor in Xanthium and other plants, serving two functions, delaying seed germination and inhibiting the growth of other plants. Most of the chemical is concentrated in the spines. When the bur is prepared as an herbal remedy, the spines are usually removed, reducing the CAT content of the finished product. [8]

How to Kill Cocklebur Weeds

Cocklebur weed management can be tricky. Of course, because of its toxicity to animals, it cannot be controlled by grazing, as many other weeds can be. There are, in fact, very few natural biological control methods for getting rid of cocklebur weeds.

The parasitic plant, dodder, may be effective in choking out cocklebur plants, but as this, too, is considered an unwanted landscape plant, it isn’t advisable. Studies have also shown that the Nupserha beetle, native to Pakistan, is effective in controlling cocklebur, but as it’s not a native species, you’ll likely not find the insect in your backyard.

The most effective methods of cocklebur control are hand pulling or chemical controls. Cocklebur plants reproduce easily by seed, which are generally dispersed on water. The seed can lie dormant in the soil for up to three years before ideal conditions cause it to germinate. Yanking out every small seedling as they appear is one option.

Chemical controls take less time. When using herbicides for controlling cocklebur, it is recommended that you use this only as a last resort.
Organic approaches are safer and much more environmentally friendly.

Cockle Burrs - garden

Common Cocklebur
Xanthium strumarium canadense
Aster family (Asteraceae)

Click on an image for a higher resolution photograph.

All photos taken at the Klein Prairie -- Murrayville, Illinois, USA

Description: This native or adventive plant is a summer annual about 2-4' tall and little branched, except for short side stems appearing from the leaf axils. The stems are round or slightly ribbed. They are often speckled with purple and have short white hairs scattered across the surface. The alternate leaves are up to 8" long and 6" across. They are cordate or ovate-cordate with bases that are well-rounded or indented and tips that are broad and blunt. Their margins are shallowly lobed or coarsely toothed, while the upper surface has a sandpapery texture. Each leaf has a long petiole that is often reddish or reddish green and about as long as the leaf blade. The petioles usually have short white hairs. A single spike-like raceme of compound flowers develops from the axil of each upper leaf. These racemes are shorter than the petioles of the leaves, often 1-4" in length. In addition, the central stem terminates in a spike-like raceme that is similar to the racemes of the leaf axils. Because Common Cocklebur is monoecious, each raceme produces several male compound flowers along its upper half, while several female compound flowers occur in the lower half. The male compound flowers are about ј" across, consisting of numerous staminate florets that have stamens with prominent white anthers. Each male compound flower occurs on a short pedicel and is slightly rounded at the top, while at the base there are 1-3 series of white floral bracts. After shedding their pollen, the male flowers quickly fade away. The female compound flowers are up to 1Ѕ" long and 1" across. Each female compound flower contains 2 pistillate florets, which are nearly enclosed by a prickly floral bract with a bur-like appearance. The female compound flowers are initially green, but turn brown as they mature and are slow to detach from the racemes. They are sessile or have short petioles. The surface of the floral bract is covered with curly white hairs, while the prickles are hooked at their tips. At the apex of each bur, there are a pair of spines that are longer and more stout than the prickles. At the base of each spine, there is a small opening for the divided style of a female flower. These styles are inconspicuous and wither away in a short period of time. The blooming period occurs during the late summer or early fall, although some plants may bloom a little earlier or later. Pollination is by wind and there is no floral scent. Each female flower within the bur-like bract produces a single oblong seed that more or less tapers to a point at each end. The seeds are often covered with dark membranes. One of the seeds in each bur has the capacity to germinate the following year, while the the germination of the second seed is delayed for at least 2 years. The root system consists of a taproot that is stout and rather woody. This plant reproduces by reseeding itself, and often forms colonies.

Cultivation: The preference is full or partial sun, moist to mesic soil, and loamy or sandy soil. Occasional flooding is tolerated if it is not too prolonged. Young seedlings of Common Cocklebur exude toxic chemicals that can inhibit germination of other species of plants, or kill off their seedlings. Individual plants become less toxic as they mature.

Range & Habitat: Common Cocklebur occurs in most counties of Illinois and is quite common (see Distribution Map). The two varieties that Mohlenbrock (2002) has described, var. canadense and var. glabratum, are both common in Illinois. The pop-up map refers to the distribution of var. canadense only. Common Cocklebur is native to both Eurasia and North America it is hard to distinguish between native and adventive races of this plant. Habitats include cropland (especially corn fields), fallow fields, the floodplain zone of rivers and ponds, degraded meadows that are poorly drained, dried-up mudholes, stabilized areas of beaches and sand dunes, vacant lots, and waste areas. Disturbed, poorly drained areas are preferred.

Faunal Associations: The flowerheads don't attract many insects because they rely on wind-pollination. The Purple Finch and Franklin Ground Squirrel reportedly eat the seeds. Deer occasionally chomp off the upper half of mature plants before the bur-like flowers form, while horses and cattle may eat mature plants with the bur-like flowers, which can result in obstruction of the gastrointestinal tract. Pigs eat young plants, which are toxic, and can be poisoned if they consume them in sufficient quantity.

Comments: Common Cocklebur resembles Arctium minus (Common Burdock) somewhat, but it has separate male and female flowers that are brownish white and green, respectively, while the latter species has perfect flowers with bright pink corollas. Because Common Cocklebur is a highly variable plant, different varieties have been identified (or even regarded as separate species in the past). The other variety of Common Cocklebur in Illinois, var. glabratum, has bur-like bracts that are nearly glabrous and they tend to be more oval-shaped and less broad than the bracts of var. canadense. Otherwise, they are very similar to each other. Another species that is adventive from the southwest, Xanthium spinosum (Spiny Cocklebur), is rarely encountered in Illinois. It has more narrow lanceolate leaves, and there is a tripartite spine at the base of each leaf.

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