Appearance''Paeonia brownii'' is a glaucous, summer hibernating, perennial herbaceous plant of 25–40 cm high with up to ten stems per plant, which grow from a large, fleshy root. Each pinkish stem is somewhat decumbent and has five to eight twice compound or deeply incised, bluish green, hearless, somewhat fleshy leaves which may develop purple-tinged edges when temperatures are low. The blades of the leaflets or segments are oval to inverted egg-shaped, 3-6 × 2–5 cm, with a clearly narrowed, stalk-like foot and an stump or rounded tip. The bisexual flowers are cup-shaped, 2–3 cm when open, nodding, and are set individually at the tip of a branching stem, and bloom for 9–15 days. Flowering occurs from March to June . The five or six overlapping sepals are a purplish green, cupped, and oval or almost circular, persist after flowering. The five to ten circular petals are usually shorter than the sepals, and grade in colour from brownish-maroon at the base, via wine red to greenish or yellowish on the edge. Each flower has 60-100 yellow stamens, consisting of filaments of 3–5 mm, that are topped by anthers of 2–4 mm long. These open in succession from the inside out shedding yellow pollen, starting from the second day. A disc consisting of about twelve fleshy cone-shaped greenish-yellow lobes of 2½-3 mm high surrounds the two to six glabrous, initially yellow-green to ultimately yellow-red carpels, each having a short style topped by a curved stigma that forms a ridge. These are receptive during the first two days that the flower is open. Fertilised carpels mature into 2–4 cm long follicles that have become leathery when ripe. About four seeds develop per follicle, which are yellowish-brown to black, round to oval and 6–11 mm in diameter. As all diploid peonies, ''Paeonia brownii'' has ten chromosomes .
NamingBrown's peony is most related to, and close in appearance to the California peony, with which it constitutes the section ''Onaepia''. Common characters include having rather small drooping flowers, with small petals and a very prominent disk which usually consists of separate segments, while the seeds are cylindrical rather than ovoid. ''P. browniii'' can still be easily distinguished from ''P. californica'' however, the latter having 35–75 cm high stems bearing seven to twelve leaves which are green, while the leaflet blade gradually eases into the leaflet stalk or lacks such a stalk all together, and the finest lobes are lanceolate or narrowly elliptic. ''P. brownii'' is usually only 20–40 cm high, has six to eight glaucous leaves per stem that suddenly narrow at their base and the finest segments are egg-shaped. In ''P. californica'' the petals are egg-shaped, and about 1½-2½ cm long, reaching beyond the sepals, while in ''P. brownii'' the petals are circular or wider than long, and about ¾-1½ cm long, definitely shorter than the sepals.The species is named after Scottish botanist Robert Brown.
DistributionBrown's peony grows in open dry pine forests such as with Ponderosa Pine, in sagebrush, in mountain brush, and in aspen stands at elevations of 200–3000 m, where winters are long and cold with little or no snow cover and the growing season is short. It occurs in northern California, Idaho, Montana, Nevada, Oregon, Utah, Washington and Wyoming. It is not native to Canada.
HabitatIn the Blue Mountains at about 1050 m altitude, ''P. brownii'' grows in an upland prairie on basalt-substrate close to conifer stands. In addition to a variety of grasses, the surrounding vegetation includes western monkshood, Hooker's and arrowleaf balsamroot, redstem ceanothus, pinkfairies, hairy clematis, dwarf larkspur, parsnipflower buckwheat, fernleaf and nineleaf biscuitroot, sulphur lupine, beardtongues species, virgate scorpion-weed, sticky and slender cinquefoil, sagebrush buttercup, dwarf and Nootka rose, common snowberry, American vetch and northern mule's ears. Brown's peony avoids drought by dying down completely in early summer, after flowering and surviving underground with stores of nutrients and energy in its thick rootstock. When parts of the plant are broken, bruised or damaged by predation it produces a pronounced bitter and unpleasant scent. Plants are rarely eaten, but caterpillars of the species ''Euxoa ustula'', dark grey fishia and small heliothodes moth have been found to eat 1–2 mm holes in the flowers, although these species are better known from other host plants. Flowers give off the same smell more weakly and the lobes of the disc secrete a sweet nectar with a bitter aftertaste over the entire time the stigmas and anthers are fertile.
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