Prickly russian thistle

Appearance

''Kali tragus'' is an annual forb. In habit, the young plant is erect, but it grows into a rounded clump of branched, tangled stems, each one up to about a metre long.

Depending on the plant's genetics and condition, the leaves and stems may be green, red, or striped, and they may be hairless or pubescent. The leaves are tipped with spines that in most varieties are so sharp that the plants are best handled with gloves and other suitably protective clothing, though some genetic variants have only a hair at the tip.

On the young plant, leaves may be more than 5 cm long, succulent and more or less cylindrical; these juvenile leaves are deciduous and drop off as the plant matures. The leaves of the mature plant are persistent, leathery, broader and shorter than the young leaves , rigid and spine-tipped. They remain on the stem till the plant dies at the end of the season. In the axil of the mature leaf, there are two leaf-like bracts with a flower between them. The flower lacks petals, but is surrounded by a disk of wide, winged sepals, whitish to pink in color.

Distribution

''Kali tragus'' is native to Eurasia, but in the 1870s, it appeared in South Dakota when flaxseed from Russia turned out to be contaminated with ''Kali'' seeds. Although it is the best-known of this group of weeds, and was at first thought to be a single well-defined species, it now is known to have included more than one species plus some hybrids. This has led to taxonomic confusion in dealing with species in the genera ''Salsola'' and ''Kali'' in America. Recent studies show that the population that once was assigned to ''Salsola tragus'' really includes three or more morphologically similar species that differ in flower size and shape. The group was widely assigned to the family Chenopodiaceae, but the Chenopodiaceae – including the genera ''Kali'' and ''Salsola'' – have since been included in the Amaranthaceae. They now are allocated to the Salsoloideae, a subfamily of the Amaranthaceae.

''Kali tragus'' proved to be highly invasive as an introduced species and rapidly became a common ruderal weed of disturbed habitats in many regions of North America, particularly in the Midwest. The species also has become naturalized in various regions of Central and South America and in parts of Southern Africa and Australia. It now occupies a wide variety of habitat types in those regions and often is the first or even the only colonizer in conditions where no local species can compete successfully. Because of its preference for sand and its tolerance of salinity, it commonly grows along sea beaches as well as in disturbed grassland and desert communities, especially in semiarid regions.

Habitat

''Kali tragus'' is a ruderal annual forb. It germinates rapidly even in very small amounts of moisture in arid conditions. When young it may be grazed freely, but that phase lasts for only a brief period, and generally at a time when other forage is relatively plentiful. After this it becomes a weed in most contexts. One reason is that as they mature most varieties become too spiny and woody for most stock to browse. As its fruits mature, the plant dies, dries and becomes hard and brittle. It is in this state that it is likely to detach from its root and become a tumbleweed. As tumbleweeds go, it is very large, often a metre or more in diameter, spiny, largely inedible to most livestock if unprocessed, and a fire hazard. However, in regions where there is plentiful winter rain, the moisture softens both the twigs and the spines, after which hardy breeds of livestock and some wildlife species once again will eat it.

''Kali tragus'' has acquired a bad reputation for its spininess, its woodiness when mature, and its general ecological competitiveness, augmented by its tumbleweed nature, which enables it to spread rapidly over open ground. During the past century or more, the majority of the publications that dealt with the topic have discussed its pernicious nature, the increasing threats that the species poses, and how to combat its invasiveness; they largely have ignored its other attributes.

However, even early publications did concede that the plant is of value as a forage in severely arid conditions where few other forage species are viable. As for its harmful competitiveness, most authors emphasised its invasiveness, though some did mention its value in regenerating overgrazed or otherwise abused land.

Apart from its value to domestic cattle and sheep in some regions, ''Kali tragus'' is a source of food and shelter for several species of wild life. Its nutritional value is high; it is rich in various minerals, Vitamin A, and phosphorus. It is a minor forage component for bison, mule deer, and wapiti. Pronghorn eat it with reluctance in drought conditions, but feed on it avidly under rainy conditions, especially in wet years. Prairie dogs consume it as a major food wherever they encounter it. Seed-eating birds and small mammals such as rodents feed on the seeds.

For some species of wildlife, ''Kali tragus'' offers useful shelter. Medium-sized deer species make some use of it, but it is mainly of value to small mammals and bird species that normally live close to the ground and shelter under bushes.

Some livestock species such as camels and some breeds of stock that are adapted to semi-desert conditions will brave the spines when forage becomes scarce. For instance, many goats and some breeds of sheep such as karakul browse the bushes. Furthermore, like many members of the Amaranthaceae, the plant is rich in high-quality proteins, with a good balance of essential amino acids, and the seed even more so.

''Kali tragus'' and many related species, including some that are widely regarded as invasive weeds in other countries, are valued in their regions of origin. They are adapted to inhospitable environments that do not support many other forage species. In – for example – Uzbekistan, stems, fruits and leaves are valued as nutritious year-round camel feed; sheep and goats browse it in summer for preference, but also to some extent in autumn and winter. The fruits are important for fattening camels, goats, and karakul sheep; the fruit may partially substitute for concentrates, especially in autumn and winter. In those regions annual ''Kali'' species are known as "solyanki"; they are important as drought- and salt-tolerant forage and form a dominant group in the flora and vegetation of the most challenging environments. Some are useful for stabilising shifting sands and for rehabilitation of degraded rangelands such as the saline soil of the red desert of Kyzyl Kum. Some of the species also invade ruderal sites or occur as weeds in cultivated fields.

Although ''Kali'' still has not won much recognition in contemporary first-world livestock nutrition, this might reflect short memories rather than shortage of evidence for its merits; during the Dust Bowl era, it was credited with having rescued beef cattle husbandry in North America. The usual hay crops had failed and when all other sources failed farmers fed their cattle on tumbleweed.

Reproduction

The plant becomes woody as the fruits develop. As they ripen, the plant begins to die, dries out and becomes brittle. In that state the base of the stem breaks off easily, particularly in a high wind. The plant then rolls readily before the wind and disperses its seeds as a tumbleweed.

A large specimen of ''Kali tragus'' may produce some 200,000 seeds.

Cultural

''Kali tragus'' is a ruderal annual forb. It germinates rapidly even in very small amounts of moisture in arid conditions. When young it may be grazed freely, but that phase lasts for only a brief period, and generally at a time when other forage is relatively plentiful. After this it becomes a weed in most contexts. One reason is that as they mature most varieties become too spiny and woody for most stock to browse. As its fruits mature, the plant dies, dries and becomes hard and brittle. It is in this state that it is likely to detach from its root and become a tumbleweed. As tumbleweeds go, it is very large, often a metre or more in diameter, spiny, largely inedible to most livestock if unprocessed, and a fire hazard. However, in regions where there is plentiful winter rain, the moisture softens both the twigs and the spines, after which hardy breeds of livestock and some wildlife species once again will eat it.

''Kali tragus'' has acquired a bad reputation for its spininess, its woodiness when mature, and its general ecological competitiveness, augmented by its tumbleweed nature, which enables it to spread rapidly over open ground. During the past century or more, the majority of the publications that dealt with the topic have discussed its pernicious nature, the increasing threats that the species poses, and how to combat its invasiveness; they largely have ignored its other attributes.

However, even early publications did concede that the plant is of value as a forage in severely arid conditions where few other forage species are viable. As for its harmful competitiveness, most authors emphasised its invasiveness, though some did mention its value in regenerating overgrazed or otherwise abused land.

Apart from its value to domestic cattle and sheep in some regions, ''Kali tragus'' is a source of food and shelter for several species of wild life. Its nutritional value is high; it is rich in various minerals, Vitamin A, and phosphorus. It is a minor forage component for bison, mule deer, and wapiti. Pronghorn eat it with reluctance in drought conditions, but feed on it avidly under rainy conditions, especially in wet years. Prairie dogs consume it as a major food wherever they encounter it. Seed-eating birds and small mammals such as rodents feed on the seeds.

For some species of wildlife, ''Kali tragus'' offers useful shelter. Medium-sized deer species make some use of it, but it is mainly of value to small mammals and bird species that normally live close to the ground and shelter under bushes.

Some livestock species such as camels and some breeds of stock that are adapted to semi-desert conditions will brave the spines when forage becomes scarce. For instance, many goats and some breeds of sheep such as karakul browse the bushes. Furthermore, like many members of the Amaranthaceae, the plant is rich in high-quality proteins, with a good balance of essential amino acids, and the seed even more so.

''Kali tragus'' and many related species, including some that are widely regarded as invasive weeds in other countries, are valued in their regions of origin. They are adapted to inhospitable environments that do not support many other forage species. In – for example – Uzbekistan, stems, fruits and leaves are valued as nutritious year-round camel feed; sheep and goats browse it in summer for preference, but also to some extent in autumn and winter. The fruits are important for fattening camels, goats, and karakul sheep; the fruit may partially substitute for concentrates, especially in autumn and winter. In those regions annual ''Kali'' species are known as "solyanki"; they are important as drought- and salt-tolerant forage and form a dominant group in the flora and vegetation of the most challenging environments. Some are useful for stabilising shifting sands and for rehabilitation of degraded rangelands such as the saline soil of the red desert of Kyzyl Kum. Some of the species also invade ruderal sites or occur as weeds in cultivated fields.

Although ''Kali'' still has not won much recognition in contemporary first-world livestock nutrition, this might reflect short memories rather than shortage of evidence for its merits; during the Dust Bowl era, it was credited with having rescued beef cattle husbandry in North America. The usual hay crops had failed and when all other sources failed farmers fed their cattle on tumbleweed.