musk thistle
Carduus nutans                                   

Identifying Characteristics:

Seed:   achene, straw-colored, oblong, glabrous, protrusion at attachment of plumeless, whitish pappus

Seedling:  basal rosette; leaves waxy, pale green, prominent veins, coarsely lobed

Mature Plant:  fibrous roots from large, shallow, fleshy, corky, hollow taproot; erect stem, branched, spiny, winged appearance, spine at tip of each lobe; alternate leaves, dark green with light green midribs and white margins, spines prominent on each lobe, white or yellow; mostly solitary inflorescence heads nodding at ends of branches, disk florets deep rose to violet or purple; spine-pointed tips

Method of Propagation: seed

Life Cycle: biennial or rarely annual herb

References: 
Bryson, Charles T. & Michael S DeFelice. "Weeds of the South."