Illustrator: John Myers

Copyright: Flora of North America Association

Plants pubescent or glabrous. Stems erect or decumbent, not bulbous-based, without bulbils. Roots basal, never tuberous. Leaves basal and cauline or sometimes only cauline; basal and lower cauline leaves similar, petiolate, blades undivided, lobed, or compound, segments lobed or unlobed, margins entire or dentate. Inflorescences 2-16-flowered cymes (cymes sometimes sympodial, then flowers seemingly inserted opposite bracts). Flowers pedicellate (sessile in R. platensis); sepals deciduous soon after anthesis, 5 (3 in R. platensis); petals yellow (sometimes absent in R. hebecarpus); nectary scale attached basally, free from petal for at least 1/2 its length, forming flap covering nectary, glabrous, free margin entire; style present. Fruits achenes, 1-locular; achene body discoid, strongly flattened, 3-7 times as wide as thick, not prolonged beyond seed; wall thick, spiny, tuberculate, or papillose (sometimes smooth in R. sardous); margin low or high, broad or narrow ridge; beak much shorter than achene body.

Distribution

Worldwide except lowland tropics.

Discussion

Species ca. 15 (8 in the flora).

Selected References

None.

Lower Taxa

Ranunculus arvensis, Ranunculus hebecarpus, Ranunculus marginatus, Ranunculus muricatus, Ranunculus parviflorus, Ranunculus platensis, Ranunculus sardous, Ranunculus trilobus

Key

1	Petals 1–2 mm; achenes finely papillose, papillae terminating in slender hooked hairs or spines; native or introduced.	> 2
1	Petals 4–10 mm; achenes coarsely papillose, tuberculate, or spinose, rarely smooth; introduced weeds.	> 4
2	Flowers sessile; sepals 3.	Ranunculus platensis
2	Flowers pedicellate; sepals 5.	> 3
3	Achenes ornamented on faces and margin, with lanceolate beaks; native of Pacific Slope.	Ranunculus hebecarpus
3	Achenes ornamented on faces but not margin, with deltate beaks; introduced weed, widespread in North America.	Ranunculus parviflorus
4	Sepals spreading; achenes 5–9 in single whorl, the faces and margin long-spinose.	Ranunculus arvensis
4	Sepals reflexed; achenes 10–60 in ovoid or globose heads, the faces papillose to spinose or rarely smooth, margin smooth.	> 5
5	Basal leaves compound; achene beak 0.3–0.7 mm.	> 6
5	Basal leaves simple; achene beak 1–2.5 mm.	> 7
6	Achene faces sparsely papillate or sometimes smooth; petals more than 5 mm.	Ranunculus sardous
6	Achene faces densely tuberculate; petals less than 5mm.	Ranunculus trilobus
7	Achene faces but not margin covered with long spines; beaks 2– 2.5 mm.	Ranunculus muricatus
7	Achene faces but not margin covered with high sharp tubercles or low spines; beaks ca. 1 mm.	Ranunculus marginatus