Question

Which plant is described by these clues? Each pollen sac opens not by a slit but by two small trapdoors hinging upward from the base, and the {stamen}s stand directly opposite the petals rather than alternating with them. Its flower parts run in stacked rings of three, and the berry ripens from a chamber that sat above the petals, so no withered flower scar is left on the far end of the fruit. Sharp spines stand at every node, and they are modified leaves, with the working foliage clustered in little tufts on dwarf shoots in their axils. Scratch the bark or snap a stem and the wood beneath is a vivid chrome yellow. Brush the base of a stamen with a bristle and it snaps inward across the centre of the flower, dusting whatever touched it. Its leaves are small and spoon-shaped, 0.5 to 1.2 inches (1 to 3 cm) long, with a completely smooth untoothed edge. Its spines are single and unbranched, one to a node, not divided into three points from a common base. Flowers hang in twos, threes and fours in small drooping clusters, pale yellow and flushed reddish outside, never in long many-flowered chains. Bright red ellipsoid berries about 0.4 inch (10 mm) long hang on the bare twigs well into winter, and birds carry them deep into woodland. The species epithet honours Carl Peter Thunberg, the Swedish botanist who catalogued the flora of Japan in the 1770s. The named form is simply the dark one: foliage that opens and holds deep reddish-purple all season instead of the plain green of the wild type, which is the whole reason it is planted. Sold by the million as a compact thorny hedge, it has become one of the most serious woody invaders of eastern North American forests, where its dense low thickets hold humidity at ground level and are associated with raised numbers of blacklegged ticks.

Accepted Answer

Berberis thunbergii f. atropurpurea

Name That Plant #036