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Ash Creek ivesia, Ash Creek mousetail

Shockley's ivesia, sky mousetail

Habit Plants grayish, ± matted. Plants green to grayish green, ± densely matted.
Stems

± prostrate, 0.4–1.5(–2) dm.

prostrate to ascending, 0.2–1.5 dm.

Basal leaves

tightly cylindric, (1.5–)2–5(–7) cm; sheathing base densely hairy abaxially;

petiole 0.5–4 cm;

lateral leaflets (5–)8–15 per side, overlapping at least distally, ± flabellate, 0.5–2 mm, incised to base or nearly so into (0–)3–8(–15) elliptic to narrowly obovate lobes, apex not or obscurely setose, surfaces densely hirsute, cryptically glandular;

terminal leaflets indistinct.

tightly to loosely cylindric, (1–)2–12(–14) cm; sheathing base strigose to hirsute abaxially;

petiole 0.5–4 cm;

lateral leaflets (3–)5–15(–18) per side, separate to overlapping at least distally, ± flabellate, 1–4(–6) mm, incised to base or nearly so into 2–10(–12) oblanceolate to obovate or elliptic lobes, apex sometimes setose, surfaces ± sparsely hirsute, ± glandular;

terminal leaflets indistinct.

Cauline leaves

(0–)1;

blade reduced.

(0–)1;

blade vestigial or reduced.

Inflorescences

20–200-flowered, congested, (1–)1.5–6(–10) cm diam.

2–20-flowered, ± open, 0.5–4(–6) cm diam.

Pedicels

1.5–6 mm.

3–10(–12) mm.

Flowers

4–6 mm diam.;

epicalyx bractlets 5, lanceolate to elliptic, 0.6–1.5(–2) mm;

hypanthium shallowly cupulate, 1 × 2–3 mm;

sepals (1–)1.5–2.5(–3) mm, acute;

petals white to pale yellowish, linear, 1 mm;

stamens 5, filaments 0.3–1 mm, anthers yellow with maroon margins, ovate, 0.3–0.5 mm;

carpels 1–2(–3), styles 0.7–1.8 mm.

5–10 mm diam.;

epicalyx bractlets 5, elliptic or narrowly oblong to ovate, 0.7–2(–3) mm;

hypanthium patelliform, 1–2 × 2.5–4.5(–5) mm;

sepals 1.5–3.5(–4) mm, acute to obtuse;

petals ± yellow, oblanceolate to spatulate or narrowly obovate, 1–3 mm;

stamens 5, filaments 0.8–1.8 mm, anthers yellow, oblong, 0.4–0.9 mm;

carpels 2–5(–6), styles 1.8–2.5 mm.

Achenes

brown, 0.8–1.5 mm, smooth, prominently carunculate.

greenish cream to light brown, 1.5–2.2(–2.5) mm, smooth, prominently carunculate.

Ivesia paniculata

Ivesia shockleyi

Phenology Flowering summer.
Habitat Dry shallow volcanic ash and cinders atop volcanic bedrock, open sagebrush communities, adjacent conifer woodlands
Elevation 1500–1800 m (4900–5900 ft)
Distribution
from FNA
CA
[BONAP county map]
from FNA
CA; NV; OR; UT
[WildflowerSearch map]
[BONAP county map]
Discussion

Of conservation concern.

Ivesia paniculata is known only from the Ash Valley area of Lassen County. The distinctions between I. paniculata and I. rhypara are perhaps on the same scale as variation among disjunct population clusters of I. rhypara, but no taxonomic adjustments are proposed at this time.

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

Varieties 2 (2 in the flora).

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

Key
1. Lateral leaflets: lobes 2–5(–7); inflorescences 2–10-flowered, 0.5–3 cm diam.; e California, c, se Oregon, c, n Nevada.
var. shockleyi
1. Lateral leaflets: lobes (4–)6–10(–12); inflorescences 5–20-flowered, (1–)3–4(–6) cm diam.; wc Utah.
var. ostleri
Source FNA vol. 9, p. 229. FNA vol. 9, p. 227.
Parent taxa Rosaceae > subfam. Rosoideae > tribe Potentilleae > Ivesia > sect. Setosae Rosaceae > subfam. Rosoideae > tribe Potentilleae > Ivesia > sect. Setosae
Sibling taxa
I. aperta, I. argyrocoma, I. arizonica, I. baileyi, I. callida, I. campestris, I. cryptocaulis, I. gordonii, I. jaegeri, I. kingii, I. longibracteata, I. lycopodioides, I. muirii, I. multifoliolata, I. patellifera, I. pickeringii, I. pityocharis, I. pygmaea, I. rhypara, I. sabulosa, I. santolinoides, I. saxosa, I. sericoleuca, I. setosa, I. shockleyi, I. tweedyi, I. unguiculata, I. utahensis, I. webberi
I. aperta, I. argyrocoma, I. arizonica, I. baileyi, I. callida, I. campestris, I. cryptocaulis, I. gordonii, I. jaegeri, I. kingii, I. longibracteata, I. lycopodioides, I. muirii, I. multifoliolata, I. paniculata, I. patellifera, I. pickeringii, I. pityocharis, I. pygmaea, I. rhypara, I. sabulosa, I. santolinoides, I. saxosa, I. sericoleuca, I. setosa, I. tweedyi, I. unguiculata, I. utahensis, I. webberi
Subordinate taxa
I. shockleyi var. ostleri, I. shockleyi var. shockleyi
Synonyms Potentilla shockleyi
Name authority T. W. Nelson & J. P. Nelson: Brittonia 33: 165, fig. 1. (1981) S. Watson: Proc. Amer. Acad. Arts 23: 263. (1888)
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