A Californian genus of two species, though by the splintering of these the number has been inflated to twenty in one interpretation of the genus. The generic name signifies ‘Tree poppy’. It is allied to Romneya, but differs in the entire leaves and yellow flowers.
The maximum height of 10 ft given for D. rigida is too low. It has attained 15 ft at Mount Stewart in Northern Ireland. For a note on the species by Wilfred Blunt see The Garden (Journ. R.H.S.), Vol. 101, pp. 330–31 (1976).