Keyed Out #134 — Cirsium arvense

Question 1

Dozens of tiny flowers are packed into one dense head cupped by overlapping scale-like {bracts}, not spread in a flat-topped cluster on radiating stalks.

Accepted Answer

daisy family

Question 2

Each tiny flower is a slim five-lobed tube with its pollen-bearing anthers fused in a ring around the style, not a wide bell with separate stamens.

Accepted Answer

Asteraceae

Question 3

Each dry one-seeded fruit is crowned by a {pappus} whose hairs carry fine side branches like a feather, rather than being plain unbranched bristles.

Accepted Answer

Cirsium

Question 4

Every leaf lobe ends in a sharp {spine}, yet cut stems bleed only clear sap, never white milk.

Accepted Answer

Cirsium

Question 5

The stems are smooth and green between the leaves, with no continuous spiny wings running down them.

Accepted Answer

Cirsium arvense

Question 6

It spreads by far-creeping roots that throw up new shoots every 4 to 12 inches (10 to 30 cm), forming colonies that persist for years, not a one-off plant that dies after flowering.

Accepted Answer

Cirsium arvense