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Sidalcea oregana var. calva

Oregon checkermallow

Photo is of parent taxon

coast checkerbloom, Humboldt checkerbloom

Habit Plants 0.9–1.5 m, with short, thick, rather woody taproot and branching caudex.

sometimes rooting at base, usually branched distally, often hollow but firm, base conspicuously densely bristly, hairs simple with swollen base, 1–2.5 mm.


stipules lanceolate, 10–14 × 2 mm;

petioles of basal and proximal leaves (5–)10–20(–30) cm, 3–4+ times as long as blade, reduced distally and distalmost leaves nearly sessile;

blade reniform-orbiculate, cordate, unlobed and margins merely crenate or shallowly 5–7(–9)-lobed, 3–9.5(–12) × 3–13 cm, blades distally all deeply 5–7-lobed essentially to base, hairs simple on both sides, 1–1.5 mm, distalmost blades usually 5-parted with irregularly-toothed lobes.


spiciform, dense, calyces usually overlapping, branched, 20+-flowered, 3–8 cm, little elongating in fruit, flowers and fruits overlapping;

primary peduncles (above distalmost leaf) usually equaling or shorter than mature inflorescence;

bracts linear-lanceolate, undivided, 7 mm, usually longer than young flower buds and conspicuous then, much longer than pedicels, shorter than to nearly equaling calyx.


1–2 mm.



calyx 8–10 mm, to 13 mm in fruit, stellate-puberulent, conspicuously bristly-tomentose especially on base, hairs 1.5–2.5 mm;

petals pink, 15–16 mm;

staminal column 9 mm, hirtellous-hairy;

anthers white;

stigmas 7–9.


2 mm.


5–6 mm diam.;

mericarps 7–9, 2.5 mm, sparsely puberulent with a few bristles, smooth or nearly so, margins rounded, mucro 0.5–0.7 mm.

Sidalcea oregana var. calva

Sidalcea oregana subsp. eximia

Phenology Flowering Jun–Aug(–Sep).
Habitat Meadow openings, prairies
Elevation 0–1200 m (0–3900 ft)
from FNA
[BONAP county map]

Subspecies eximia is uncommon and somewhat obscure. It was recognized by Hitchcock because of its notably accrescent and long-hirsute calyces and its robust habit and narrow range. It clearly intergrades with subsp. spicata and also strongly resembles Sidalcea setosa. There are no recent collections of subsp. eximia and only a limited number of older ones; it may be extirpated. It is known from the northern coast and North Coast Ranges in Humboldt County.

Of conservation concern.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 6, p. 349.
Parent taxa Malvaceae > subfam. Malvoideae > Sidalcea > Sidalcea oregana
Sibling taxa
S. oregana subsp. eximia, S. oregana subsp. hydrophila, S. oregana subsp. oregana, S. oregana subsp. spicata, S. oregana subsp. valida
S. oregana subsp. hydrophila, S. oregana subsp. oregana, S. oregana subsp. spicata, S. oregana subsp. valida
Synonyms S. eximia
Name authority (Greene) C. L. Hitchcock: Perenn. Sp. Sidalcea, 66. (1957)
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