Rush Skeletonweed

Rush Skeleton 1Rush Skeletonweed (Chondrilla juncea)
Herbaceous perennial or biennial, with rigid, wiry flowering stems to 1 m tall, milky sap. Plants exist as basal rosettes until flowering stems develop at maturity and rosette leaves whither. Persistent flower stems can hinder harvest machinery. Several forms (biotypes) occur, differing in leaf width, branching pattern, and flowering time. Characteristics can vary between, but rarely within populations since all reproduction is by clones (vegetative and seed apomixis). Plants are highly competitive for water and nutrients. Rush skeletonweed is also a significant problem in several other countries, particularly Australia. Introduced from southern Europe.

Seedlings
Cotyledons spatulate to oval. First leaves elliptic with backwards pointing teeth. Require a continuous moisture supply for up to 6 weeks to develop a persistent root system

Mature Plants
Rosette leaves oblanceolate, 4-12 cm long, 1-5 cm wide, prostrate, and typically lacking hairs. Margins often purple-tinged and irregularly shallow-lobed, with lobes often pointing backwards towards the leaf base. Lobes opposite one another. Terminal lobe more or less sharp-pointed. Rosettes produce 1 or more flowering stems with numerous branches. Upper stems mostly lack hairs, but typically have dense, bristly, downward pointing hairs at the base. Stem leaves often absent or bract-like, but when present resemble reduced rosette leaves

Rush Skeleton 2Root Structures
Taproot slender, deep, persistent, with short lateral branches along the length. Taproots become somewhat woody with age and can penetrate soil to depths of 2-3 m or more. Most lateral roots are short-lived, non-woody, and less than 8 cm long, but a few lateral roots near the surface can become rhizome-like and grow laterally for 15-20 cm before turning downwards. Adventitious buds near the top of the taproot and on major lateral roots can produce new rosettes. Roots are easily fragmented, with pieces as small as 1-2 cm producing new rosettes from depths to 1 m.

Flowers
July until flowering stems killed by frost (fall or winter). Flower heads axillary or terminal, sessile or short-stalked, and solitary or in interrupted spike-like clusters of 2-5. Each flower head consists of 7-12 bright yellow ligulate flowers, strap-shaped with 5-lobed corollas 12-18 mm long, and phyllaries (bracts) cylindric as a unit and in 2 unequal rows, the outer much smaller than the inner. Receptacle lacks small bracts (chaff) among the flowers. Temperatures of at least 15 ┬║C are necessary to induce flower production.

Rush Skeleton 3Habitat
Disturbed soils of roadsides, croplands, especially irrigated grain fields, semi-arid pastures, rangelands, and residential properties. Grows best on well-drained, sandy or gravelly soils in climates with cool winters and hot, relatively dry summers without prolonged drought. Tolerates a wide variety of environmental conditions, including rainfall less than 250 mm (10 in) to more than 1200 mm (~50 in), cold winter areas, and continental climates. Severe infestations are less common on heavy clay soils.

Similar Species
Rosette leaves of rush skeletonweed and dandelion share the following characteristics: leaves without hairs, leaf lobes pointing backward and opposite one another, milky juice exuded when torn. Unlike rush skeletonweed, dandelion has unbranched, leafless, hollow, non-persistent, fleshy flowering stems and seeds without small scales at the apex. In addition, dandelion is typically found in turf and gardens. Chicory (Cichorium intybus L.) is similar to rush skeletonweed and dandelion, but has rosette leaf lobes pointing outwards or forwards and not always opposite, and basal leaves with a few rough coarse hairs.

Some other look a likes include yellow sweet clover, prickly lettuce and dandelion.