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balsamroot

Habit Herbs perennial; with thick, resin-producing taproots.
Stems

erect, scapose, unbranched.

Leaves

mainly basal; simple or pinnately compound, lanceolate to ovate;

cauline opposite, sometimes 1 additional pair of reduced cauline leaves alternate.

Inflorescences

with 1 main head, occasionally with up to 6 axillary heads per stem.

Heads

radiate.

Involucres

broadly campanulate to hemispheric.

Receptacles

flat to convex, paleate.

Ray florets

pistillate;

corollas yellow or rarely pink to red.

Disc florets

bisexual;

corollas yellow, 5-lobed.

Phyllaries

in 2–4 series; outer equaling or surpassing inner.

Fruits

4-sided; black, glabrous or strigillose;

pappi 0.

Paleae

lanceolate; acute, folded around fruits.

Balsamorhiza

Distribution
[BONAP county map]
Discussion

Western Canada and United States. 12 species; 10 species treated in Flora.

Balsamorhiza is most closely related to Wyethia, from which it is distinguished by being scapose. Balsamorhiza is divided into two sections, both of which occur in Oregon. Section Artorhiza has cordate or sagittate, simple leaves; a taproot bearing multiple crowns; alternate stem leaves above the pair of opposite leaves; and often multiple heads per stem. Section Balsamorhiza has generally pinnately divided leaves (often simple in B. serrata); taproots bearing one or at most two crowns; one pair of opposite stem leaves; and a solitary head per stem. All species of Oregon Balsamorhiza have a chromosome number of n=19 and hybridize when they come together except for the polyploid B. macrophylla. Intersectional hybridization merely produces hybrid swarms, while intrasectional hybridization tends to produce widespread clines, leading to taxonomic confusion. Hybrid swarms are easily distinguished in the field by the wide variation in leaf division and pubescence within a given population. In the herbarium, when only one plant per population is present, hybrids are best distinguished by possessing leaves that are not as deeply divided as would be expected for the most similar-looking member of section Balsamorhiza, or by plants with pinnately divided leaves having either multiple heads per stem or alternate, in addition to opposite, stem leaves. Widths of heads are those of pressed specimens. Widths of pinnae are the width of full-sized pinnae from the middle of a fully developed leaf at their widest point (not including any lobes that may be present).

Source Flora of Oregon, volume 1
Subordinate taxa
B. careyana, B. deltoidea, B. hirsuta, B. hispidula, B. hookeri, B. incana, B. lanata, B. macrolepis, B. macrolepis, B. macrophylla, B. platylepis, B. platylepis, B. rosea, B. sagittata, B. sericea, B. serrata
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