Prickly Lettuce, Lactuca serriola
Family: Asteraceae; Sunflower Family
Vegetative Characteristics:
Seedling: Leaves forming basal rosette, clasping petioles, spiny edges, pale green, prominent midvein
Stems: erect, pale green or straw colored, hollow, lower stems often prickly, milky sap
Leaves: alternate, oblong-lanceolate, glaucous, clasping stem with base extended into pair of hastate projection, lobed or wavy, margins toothed and prickly, midveins prickly underneath
Reproductive Characteristics:
Inflorescences: panicle, 0.2-0.8 m long, branches widely spreading, 16-24 heads; involucres 9.0-15.0 mm long, 3.0-6.0 mm wide; ray florets yellow to pale yellow, often blue after drying; receptacle 8.0-10.0 mm diameter
Fruits: achene, flat, oblanceolate, grayish yellow to yellowish brown, 3.0-4.0 mm long, 1.1-1.5 mm wide, 5-7 lengthwise ribs on each side, ribs pubescent toward apex, beak 3.0-5.0 mm long; pappus white, 4.0-5.0 mm long, easily detached leaving a short remnant, almost always absent
Special Identifying Features
⇒ erect winter annual or biennial; stem hollow with milky sap; leaves glaucous, clasping, margins and underside of midvein prickly; ray florets yellow
