Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Rhus michauxii' from the website Trees and Shrubs Online (treesandshrubsonline.
A low, diciduous shrub up to 31⁄2 ft high, spreading by means of underground suckers; stems erect and rather stout, covered with short hairs. Leaves pinnate, 8 to 12 in. long, dull green; leaflets usually nine to fifteen, ovate or oblong, 11⁄2 to 3 in. long, rounded and slightly oblique at the base, the terminal one the largest, with a winged stalk, the upper surface hairy, the lower one covered with a dense, yellowish down, the margins coarsely toothed. Panicle erect, terminal, hairy, 6 to 8 in. high, half as much wide; flowers 1⁄8 in. wide, densely arranged, petals greenish yellow; calyx covered with grey down. Fruits nearly round, 1⁄8 in. in diameter, scarlet, very downy.
Native of the S.E. United States; first discovered by Michaux towards the end of the 18th century. For about one hundred years it was lost sight of, but was again discovered and reintroduced to cultivation. It was sent to Kew in 1901 from the Biltmore Arboretum, USA, and flowered the same year. According to some authorities it is very poisonous, perhaps the most poisonous of American sumachs, but I have spoken with Americans who regard it as harmless.