Weeds
Chondrilla juncea L. - Rush Skeletonweed
Systematic position.
Family Asteraceae Dumort. (Compositae), genus Chondrilla L.Biological group.
This is a perennial weed.Morphology and biology.
The plant has a milky juice. Root system is well developed. The plant has a simple slender taproot that can reach over 2 m, and also a great number of additional roots. This advanced root system provides the Rush Skeletonweed with access to a large volume of soil and to potentially large reserves of soil-stored water. Lateral roots are often formed in sandy or gravelly soils, and in waterlogged ground. Buds that produce daughter rosettes can be formed in the upper part of primary root or on large lateral roots near the soil surface. All parts of the root system, especially deeper parts, are brittle and easily broken, and new plants can grow from root fragments. Stems are upright; covered with stiff and reddish-brown hairs in lower part; highly branched at base, 50-100 (130) cm in height. Basal leaves are well developed, 4-13 cm long and 15-45 mm wide, forming a rosette. They are runcinate or lanceolate, retuse, pinnatifid, withering early. Stem leaves are reduced, linear, 2-10 cm long and 1-8 mm wide, and upper stem leaves are often reduced to scale-like bracts. All stem leaves are glabrous, short-dentate or smooth-edged, with sparse bristles along margin, to the base narrowed or amplexicaul. The size of leaves and pubescence varies strongly. Each leaf rosette produces 1 flowering stem with multiple branches. Flower heads are formed at the ends of branches, either individually or in groups of 2 to 5. They are collected in a narrowly paniculate inflorescence. The flower heads are fine and few-floral; each flower head has 7 to 12 flowers. Involucre is cylindrical with cobwebby pubescent. External leaflets of involucre are short and oblong-ovoid. Internal leaflets (8 in number) are long, about 10 mm long and 2-2.5 mm wide. Flowers are yellow and ligulate. Receptacle is bare. Rush skeletonweed fruits are achenes. They are oblong, 2.5-5.5 mm long (except rostellum) and 0.75 mm wide, gray-green, narrowed towards the top. The rostellum is brown and long, equal in length to achene, without articulation, not falling-away, but breaking-off. There are 5 costulae on achene surface. The pappus consists of simple, white, thin and fine-dentate hairs, 5-9 mm long. Hairs are located in 1 row. On top of the achene there is a coronet, which consists of 5 long small teeth. The plant blossoms from the end of July until autumn. Parachute-like seeds easily spread by wind. Each plant can produce up to 15000 seeds annually. Thus, the potential seed production has been estimated at 70000 seeds per m2.Distribution.
General distribution includes Southern and Middle Europe, the Mediterranean, Middle East and Western Asia. The species was described to be from Western Europe. It is a foreign plant in America and Australia. Rush Skeletonweed was first reported in North America in 1872 and in Australia in 1918. Distribution in the USSR includes: the European part, Crimea, the Caucasus, and sometimes the mountains of Central Asia and Western Siberia. According to several authors, the Rush Skeletonweed is thought to have originated in a submontane region surrounding the Caspian Sea; from there it has spread westward. Now its "natural range" extends from Western Europe and North Africa to central Asia.Ecology.
Rush skeletonweed appears to favor coarse-textured, well-drained soils such as sand dunes, granite outcrops, and other coarse soils. In all parts of its native range the soils inhabited by the Rush Skeletonweed appear to be calcareous or only mildly acidic. In general, the soils with dense herbage of the weed found in Mediterranean Europe have a relatively high percentage of sand, being poor in nutrients. In the western Mediterranean, the maximum Rush Skeletonweed density appears in areas with relatively hot and dry summers, but without heavy drought, with average precipitations of 400-700 mm being relatively evenly distributed throughout the year. The elevation range of the Rush Skeletonweed is from close to sea level up to 1550 m in Central and Southern Europe and up to 1800 m in Armenia. Between the Caspian Sea and Mongolia the Rush Skeletonweed is only found in areas of elevated land rather than in the surrounding low-lying steppe. In its native range, the species is found between 35 degrees and 55 degrees N. The Rush Skeletonweed is characteristic of needle grass-sagebrush steppe (Achnatherum/Stipa-Artemisia) in Russia, Iraq, and Anatolia. It occurs in various open semi-natural communities in the Mediterranean Region and in the upper oak scrubs in Iraq. It grows in thin pine forests on sandy soils in Russia. The Rush Skeletonweed is recorded in the mountains of Armenia together with Juniperus oxycedrus and Stipa szovitsiana. The species grows in Eurasia between 35 and 55 degrees N in steppe and semi-desert zones on sandy soils. According to some authors, dense stands of the Rush Skeletonweed are rarely found, because areas of optimal climate are limited, and only small areas of suitable sandy soil are available. The type of cultivation (wheat/fallow) favoring dense stands of this weed is rarely practiced.Economic significance.
This is a rubber-bearing plant, occasionally littering crops between 35 and 55 degrees N in steppe and semi-desert zones on sandy soils. It is more abundant in crops of wheat and on fresh fallow lands. For example, in Greece the Rush Skeletonweed is sparse (1 plant/100m2) in continuously cultivated lands, being more common in cereals (2-7 plants/m2) and the most abundant in recently abandoned fields (30-60 plants/m2). Population density is lowered in long abandoned and rough pasture stations (2-20 plants/m2).Control measures.
Regular destruction of rhizomes of the weed with the help of appropriate types of soil treatment and herbicides is necessary. Do not contaminate sowing material or ground with seeds of the weed. Mow off or pull up the weed before fructification. Agronomical actions are directed at weakening the weed, using periodic pruning of roots. It is necessary to remember that good results in controlling this weed can only be reached with a combination of agronomical and chemical methods. The use of biological enemies of the weed is also useful.Reference citations:
Keller B.A., Ljubimenko V.N., Maltsev A.I., Fedtshenko B.A., Shishkin B.K., Rodzevic R.Yu., Kamenski K.V., eds. 1935. Weed plants of the USSR. V. 4. Moscow - Leningrad: AN USSR. 414 pp. (In Russian)McVean D.N. 1966. Ecology of Chondrilla juncea L. in south-eastern Australia. Journal of Ecology 54(2): 345-365. (In English)
Wapshere A.J., Hasan S., Wahba W.K., Caresche L. 1974. The ecology of Chondrilla juncea in the western Mediterranean. Journal of Applied Ecology. 11(2): 783-799. (In English)