Russian Thistle: stems are often red or purple striped; seedling leaves long, fleshy; later leaves short; flowers inconspicuous.

• A. St. John's Wort
• B. Common Mullein
• C. Russian Thistle
• D. Larkspur

Answer: (C)

This question checks how plant morphology and growth stage traits are used to identify species in rangeland contexts. The combination of red or purple striped stems, seedling leaves that are long and fleshy, followed by shorter later leaves, and inconspicuous flowers points to Russian thistle. This plant starts with fleshy, elongated cotyledonary or seedling leaves and, as it matures, develops a form with smaller leaves while the stem coloration remains notable as red or purple stripes; its flowers are small and not showy, which makes them easy to overlook in the field but consistent with this species’ appearance.

St. John’s Wort would typically show bright yellow flowers and a different leaf arrangement. Common mullein has a rosette of large, fuzzy leaves at the base and a tall flowering stalk with conspicuous flowers. Larkspur features more elaborate, often showy flowers and leaves that are deeply lobed. None of these match the described progression of leaf form and the muted flowers seen in Russian thistle.