Helianthus ciliaris DC.
Texas Blueweed| Category |
|---|
| Forb/Herb |
Description
Stem
A rhizomatous, herbaceous perennial, 30 to 70 cm tall, its roots can reach as deep as two meters into the soil. The stems and foliage are downy and bluish green, accounting for the common name Blueweed. Plants appear as large clumps, covered with yellow flower heads, due to numerous shoots formed from the underground rhizomes.Leaves
Leaves are narrowly linear or lanceolate and sessile leaves, mostly opposite, 3 to 10 cm long, with a wavy ciliate margin.Flowers
The flower heads, 2 to 4 cm across, have yellow ray florets and reddish disk florets; they are borne singly (or few) on numerous long axillary shoots.Fruit
The fruits are greyish-brown achenes, four-angled, about 3 mm long, without pappus, resembling a small sunflower seed.Life History
Helianthus ciliaris is a robust, deep-rooted rhizomatous perennial plant, which has shown its persistence and invasiveness in its native range as a crop weed. Although herbicides can be used effectively against it, control is still troublesome, as for any persistent rhizomatous perennial. Blueweed has spread accidentally to other areas in USA where it also behaves as a noxious weed, but the long-distance invasion pressure does not seem very high. Blueweed is certainly to be seen as a plant with a high potential to become an invasive weed in many countries around the world, if it should be accidentally introduced.Helianthus laciniatus is a similar non-weedy species, which has probably contributed its genome to hexaploid clones of H. ciliaris which are more drought-tolerant.