Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Iva frutescens' from the website Trees and Shrubs Online (treesandshrubsonline.
A sub-shrub with stems somewhat fleshy, 3 to 10 ft high, branched at the upper parts; shoots minutely downy. Leaves opposite, nearly stalkless, oblong-lanceolate, pointed, rather strongly toothed, cuneate, 4 to 6 in. long, 1 to 2 in. wide, three-veined, being reduced in size upwards until, in the flowering parts, they become small and linear. Inflorescence terminal, more or less pyramidal; flower-heads greenish white, 1⁄6 in. wide, hemispheric, axillary, each consisting of staminate and four to five pistillate flowers and beset by four or five broadly ovate bracts.
A native of the S. United States; introduced in 1711. It is mostly found growing in salt marshes and muddy sea-shores, and although quite hardy has little to recommend it for gardens. Both the typical variety and the following one are in cultivation, as well as intermediates between them.