Lygodesmia juncea (Pursh) D. Don ex Hook.

Skeleton Plant

Lygodesmia juncea plant

Family - Asteraceae

Stems - To 50cm tall, glabrous, often glaucous, erect, branching (branches erect and parallel to main axis), multiple from a thick woody rhizomatous rootstock, with vertical striations. Plant with milky sap.

Leaves - Alternate. Cauline leaves reduced and scalelike, +/-7mm long, scabrous, subulate. Basal leaves few (if any), linear-lanceolate, to +3cm long.

Inflorescence - Single flower head terminating the stem. Flowerheads typically with 5 flowers per head.

Involucre - To 1.4cm long(tall), with 2-3 series of outer phyllaries and 1 long inner series of phyllaries. Phyllaries glabrous, with scarious margins, typically with a brownish tip. Outer phyllaries acute, 2-3mm long. Inner phyllaries to 1.3cm long, 2mm broad, linear.

Lygodesmia juncea involucreInvolucre.

Ray flowers - Fertile, perfect. Ligules pinkish-purple, to +1cm long, typically 5-toothed(notched) at apex, glabrous. Corolla tube white, 1cm long, glabrous. Style purplish, bifurcate. Anthers connate around style, purplish, to 4mm long. Achenes glabrous, angled, greenish, 1.7mm long in flower, 1cm long in fruit. Pappus of capillary bristles.

Disk flowers - Absent.

Lygodesmia juncea flowers

Flowering - June - August.

Habitat - Exposed dry loess hills.

Origin - Native to U.S.

Other info. - Although I have not seen it myself, this species is frequently seen with globose galls caused by a small wasp. Galls are not actually caused by the insect larvae themselves, rather, galls are formed by a soil-borne bacteria carried on the insect larvae. The bacteria is known as Agrobacterium tumefaciens and is widely used in genetic recombination techniques with plants. There is a wealth of information out there if you want to read more about A. tumefaciens.
L. juncea is not common in Missouri. It can only be found growing wild in the extreme northwest corner of the state. The plant is common in the west and southwest U.S. however.

Photographs taken at the Jamerson C. McCormack Conservation Area, Holy County, MO., 6-30-00.