Question

Which plant is described by these clues? Each of its six {stamens} sheds pollen not through a lengthwise slit but through two small trapdoors that hinge upward off the {anther}. Brush the base of a {filament} and the {stamen} swings inward in about half a second, dabbing pollen onto the visitor before it can settle in. The flower is built in threes doubled: three {sepals} with three more behind them, six {petals} in two ranks, and six {stamens} to match. Cut a stem or scrape a root and the wood beneath the bark is a startling sulphur-yellow, stained by a fiercely bitter {alkaloid}. At every {node} a stiff needle-sharp {spine} stands guard, and it is not a twig but a leaf remade as a weapon, with the true blades tufted in its {axil}. It comes from the mountain slopes and forest margins of Japan, from near sea level to about 5,000 feet (1,500 m). Its small spoon-shaped blades run perfectly smooth around the edge, without a tooth or a bristle anywhere on the margin. Pale yellow bells hang two to five together in drooping bunches barely 0.4 to 0.6 inch (10 to 15 mm) long, half hidden beneath the shoots in mid-spring. Glossy red one-seeded berries 0.3 to 0.4 inch (7 to 10 mm) long cling to the bare twigs all winter, and the birds that carry them off have driven the plant deep into North American woodlands, where several states now ban its sale. The genus name reached Latin from an Arabic word for the fruit, while the species honours the Swedish botanist who collected in Japan in the 1770s. The named form it belongs to means simply dark purple, which is what the foliage holds all summer before turning orange-red in autumn. Sold everywhere as a knee-high burgundy mound for sunny front gardens, this dwarf, deer-proof, thorn-armed shrub has become notorious for sheltering ticks in the woodlands it escapes into.

Accepted Answer

Berberis thunbergii f. atropurpurea 'Atropurpurea Nana'

Name That Plant #039