Romneya coulteri

Also known as Matilija or Californian tree poppy, this dramatic shrubby perennial provides a spectacular display in the AGM Border, above the top of the Thompson Road drive. Six crepe-papery white petals centred with a cluster of golden stamens form huge, slightly scented flowers atop 2-metre tall stems with glaucous foliage.

Although difficult to propagate and sometimes to establish, once it does the plant can spread vigorously via rhizomes. It is under threat in Californian coastal scrub but also grows to 3,600ft in the Santa Ana Mountains.
The Irish botanist and explorer Dr Thomas Coulter found Romneya on expeditions to California and introduced it to cultivation, first flowering in the National Botanic Gardens in Dublin in 1875.