Romneya coulteri

{{short description|Species of flowering plant in the poppy family Papaveraceae}}

{{Speciesbox

| image = Paul de Longpré00.jpg

| genus = Romneya

| species = coulteri

| authority = Harv.

}}

Romneya coulteri, the Coulter's Matilija poppy{{PLANTS|id=ROCO|taxon=Romneya coulteri|accessdate=22 October 2015}} or California tree poppy, is a perennial species of flowering plant in the poppy family (Papaveraceae). Native to southern California, USA, and Baja California, Mexico, it grows in dry canyons in chaparral and coastal sage scrub plant communities, sometimes in areas recently burned.[http://www.rareplants.cnps.org/detail/1430.html California Native Plant Society Rare Plant Profile] It is a popular ornamental plant, kept for its large, showy flowers.

The specific epithet coulteri commemorates Thomas Coulter, an Irish botanist and explorer.{{cite book|last=Harrison|first=Lorraine|title=RHS Latin for gardeners|year=2012|publisher=Mitchell Beazley|location=United Kingdom|isbn=9781845337315|pages=224}}

This herbaceous perennial may exceed {{convert|2|m|ft|0|abbr=on}} in height, its stem growing from a network of rhizomes. The gray-green, waxy-textured leaves are each divided into a few lance-shaped lobes, the blades growing up to 20 centimeters (7.8 in) long. The inflorescence is a large, solitary flower with three sepals and six crinkly white petals each up to {{convert|10|cm|0|abbr=on}} long and almost as wide, {{cite book | last1= Munz | first1= Philip A. |last2=Keck | first2= David D. | date= 1959 | title= A California Flora | location= Berkeley, Calif. | publisher= Univ. of Calif. Press | page= 194-195 }} for a total width of up to eight inches (twenty cm), the largest of any California wildflower. At the center of the flower is a cluster of many yellow stamens. The fruit is a bristly capsule, {{convert|3|-|4|cm|0|abbr=on}} long, containing many tiny seeds.

This plant often grows aggressively once planted. It spreads clonally by underground rhizomes and can appear several feet away from the original plant.{{Cite web|url=http://www.smmflowers.org/bloom/species/Romneya_coulteri.htm|title=Wildflowers, NPS, SAMO NRA - Romneya coulteri detail page|website=www.smmflowers.org|access-date=2017-06-16}}

This plant bears the largest flowers of any species native to California, rivaled only by Hibiscus lasiocarpos.[http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=220011716 Flora of North America] It was nominated for the honor of California state flower in 1890, but the California poppy won the title in a landslide.Clark, C. [https://www.cpp.edu/~jcclark/poppy/history.html Genus Eschscholzia: History]

In cultivation in the UK, Romneya coulteri and the cultivar 'White Cloud'{{cite web

| url = https://www.rhs.org.uk/Plants/74133/i-Romneya-coulteri-i-White-Cloud/Details

| title = RHS Plantfinder - Romneya coulteri 'White Cloud' | accessdate = 10 October 2018}} have gained the Royal Horticultural Society's Award of Garden Merit.{{cite web | url = https://www.rhs.org.uk/Plants/21715/i-Romneya-coulteri-i/Details | title = RHS Plantfinder - Romneya coulteri | accessdate = 10 October 2018}}{{cite web | url = https://www.rhs.org.uk/plants/pdfs/agm-lists/agm-ornamentals.pdf | title = AGM Plants - Ornamental | date = July 2017 | page = 88 | publisher = Royal Horticultural Society | accessdate = 9 October 2018}}