Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Dendromecon harfordii' from the website Trees and Shrubs Online (treesandshrubsonline.
An evergreen shrub 8 to 10 ft high with erect or arching branches. Leaves crowded on the stems, elliptic to oblong-ovate, 1 to 3 or 4 in. long and about half as wide, rounded at the apex. Flowers yellow, up to 3 in. across, borne singly on the ends of side-shoots as in D. rigida but on shorter pedicels.
Native of California, found there only on the islands of Santa Cruz and Santa Rosa; first described in 1873 but not introduced to cultivation in the U.S.A. until 1933, after which it gradually became known to Californian gardeners (E. K. Balls in Gard. Chron., 7th May 1960). Not in cultivation in the British Isles, so far as is known.
Synonyms
D. rhamnoides Greene
D. arborea Greene