buttercups

genus Ranunculus

Member of buttercup family (family Ranunculaceae)
dicots (class Magnoliopsida)
flowering plants (subphylum Angiospermae)

Except for extremely rare examples that I don't expect to encounter, there are no other wild species of this genus in the bay area.

Key features:

stem angle, rooting at nodes or not, growing from water/mud or not
petal number, length
leaf shape, especially submerged leaves
receptacle bristly or glabrous

creeping buttercup
Ranunculus repens

stems decumbent or creeping, rooting at nodes
5 petals, yellow
leaf ternate
Foothills, Wilder

lobb’s aquatic buttercup
Ranunculus lobbii

stem low from water or mud
5 petals, 4–6 mm long, 2–5 mm wide, white
floating leaves deeply 3-parted
submerged leaves generally 2–3-dissected

common water-crowfoot
Ranunculus aquatilis

stem low from water or mud
5 petals, 4–7 mm long, 1–5 mm wide, white
floating leaves not described
submerged leaves generally 3–6-dissected

cursed crowfoot
Ranunculus sceleratus

stem erect from water or mud
3–5 petals, 2–5 mm long, 1–3 mm wide, yellow
very rare: Mt. Diablo

See also rough-fruited buttercup (Ranunculus muricatus) below for another potentially aquatic buttercup.

california buttercup
Ranunculus californicus

stems erect to ascending or decumbent (prostrate), generally not rooting at nodes
9–17 petals, 7–14 mm long, 2–6 mm wide, yellow
very common

Difficult buttercups

These buttercups all have ≤ 7 petals and potentially grow erect from land. Jepson distinguishes these buttercups by fruit. If you find any with fruit, consult Jepson. Here I’ve tried to distinguish them by flower and leaf characteristics. They are sorted here by petal length.

straightbeak buttercup
Ranunculus orthorhynchus

stem erect to decumbent
5–6 petals, 8–18 mm long, yellow adaxially, yellow or red abaxially depending on subspecies
receptacle bristly
Pleasanton Ridge, Chabot

sacramento valley buttercup
Ranunculus canus

stem erect to decumbent
5–7 petals, 6–12 mm long, 3–6 mm wide, yellow
receptacle glabrous
basal and proximal cauline leaves 3-parted, segments 1–3-lobed
Mission Peak, Sunol, Mt. Diablo

western buttercup
Ranunculus occidentalis

stem erect to decumbent
5–6 petals, 5–10 mm long, 3–6 mm wide, yellow
receptacle glabrous
basal and proximal cauline leaves 3-parted or 1-ternate, ultimate segments entire or dentate
Sierra Azul, Del Valle, Mt. Diablo

rough-fruited buttercup
Ranunculus muricatus

stem erect to prostrate, from ground or water
5 petals, 4–8 mm long, 2–4.5 mm [wide], yellow
receptacle bristly
common

woodland buttercup
Ranunculus uncinatus

stem erect
5 petals, 2–4 mm long, 1–2 mm wide, yellow
receptacle glabrous
rare

pubescent-fruited buttercup
Ranunculus hebecarpus

stem erect
0–5 petals, 1.3–2 mm long, 0.3–0.7 mm wide, yellow
receptacle glabrous

Toxicity of buttercup, ranunculus (Ranunculus spp.):
1 – Skin contact with these plants can cause symptoms ranging from redness, itching, and rash to painful blisters like skin burns.
3 – Ingestion of these plants is expected to cause nausea, vomiting, diarrhea and other symptoms that may cause illness but is not life-threatening.

3 observed taxons / 9 unobserved taxons / 2 keys

Chris’s observations: 79 (50 are research grade)

Locations:

Henry Coe SP: 16
Calero CP: 8
Edgewood Park & Natural Preserve: 8
Joseph D. Grant CP: 5
Santa Teresa CP: 5
Almaden Quicksilver CP: 4
Coyote Lake / Harvey Bear Ranch CP: 3
Coyote Valley OSP: 3
Sierra Azul OSP: 3
Hidden Villa, Los Altos Hills: 2
Mission Peak RP: 2
Pacheco SP: 2
Pleasanton Ridge RP: 2
Rancho Cañada del Oro OSP: 2
Russian Ridge OSP: 2
Stevens Creek CP: 2
Coal Creek OSP
Fort Ord NM
Máyyan 'Ooyákma Coyote Ridge OSP
Picchetti Ranch OSP
Purisima Creek Redwoods OSP
Sanborn CP
Skyline Ridge OSP
Sunol Wilderness RP
Sweeney Ridge National Recreation Area
Waterdog Lake & Open Space

Months:

Jan.: 2
Feb.: 8
Mar.: 24
Apr.: 31
May: 10
Jun.: 4

For more details, use advanced search.

Taxon info: iNaturalist – Calflora – Jepson eFlora – FNA

Bay Area species: iNaturalist – Calflora