Ranunculaceae

Genus Ranunculus

General characteristics of the Genus Ranunculus.

Leaves: Cauline leaves on the older (lower) part of stems are alternate. On the younger (upper) part of stems leaves may seem to be opposite or whorled.
Flowers: Solitary or somewhat corymbed, the flowers are usually yellow but in a few species they are white. Petals are mostly 5 with a necteriferous spot at the base. Stamen are mostly numerous. [For a more complete description see: FNA]

A short key for the species found in Iowa

  1. Aquatic species (in fresh water) or amphibious
    1. Flowers; white 3 to 5 mm. across, at waters surface ----- ----------- R.trichophyllus - (threadleaf crowfoot)
    2. Flowers: white, petals yellow at base, 4-9mm. long ----------------- R. longirostris - (longbeak buttercup or white water-buttercup)
    3. Flowers: yellow, petals 7-15mm. long ---------------------------- R.flabellaris - (yellow water-buttercup)
    4. Flowers yellow; Basal leaves 3 parted, smooth; fruit head cylindric ------ R. sceleratus - (cursed buttercup)
    5. Flowers yellow; submersed leaves nearly orbicular, petals 3.5 to 5 mm long---- R. gmelini - (Gmelin's buttercup)
  1. Terrestrial Species (dry or moist soil)
    1. Petals less than 5 mm long. (small flowered plants)
      1. Plants parts generally glabrous (smooth)
        1. Flowers yellow, petals and filaments small; basal leaves kidney shaped edges round toothed; fruit heads globular------------------------- R. abortivus - (littleleaf buttercup)
      1. Plants hairy; flowers yellow,
        1. Achenes ribbed
          1. Stems erect or ascending, 0.1-1.2 m. high, soft hollow, spreading hirsute or hispid (stiff-bristly hairs), branching, 3-many flowered; sepals bristly outside, reflexed, 2.5-5.5 mm. long; petals pale yellow, fading whitish, 2.5 mm. long, 1.3-3 mm. wide; achenes numerous, thin.--------------- R. pensylvanicus - (Pennsylvania buttercup)
        1. Achenes not ribbed
          1. Beak of achene long recurved and hooked------------------ R. recurvatus - (blisterwort)
          2. Stems ascending declined or trailing, soft and hollow, hispid or hirsute (stiff-bristly hairs), 2-24 flowered, 0.2 to 1.2 m. long; radical leaves hispid-petioled, glabrous or sparingly hispid, ternately compound; cauline leaves scattered, similar; sepals hispid, reflexed; petals deep yellow, 3.5-6 mm. long, 2.5-5 mm. broad; achenes strongly flatttened------------------- R. macounii - (Macoun's buttercup)
    1. Petals longer than 5 mm. (distinctly longer than sepals)
      1. Plants; low running (5-15 cm.). Flowers; yellow, petals 6-8 mm. long, on slender erect stalks. achenes; ribbed. ---------------------------- R. cymbalaria - (alkali buttercup)
      1. Plants; erect.
        1. Achenes not flattened, dry prairies, basal leaves entire ------------------------------ R. rhomboideus
        1. Achenes strongly flattened, beaks long- more than half the length of the achene.
          1. stems; weak, silky-gray, 1-2 dm. tall, leaves; divided into leaflets, flowers; light yellow, petals oblong, 6-15 mm. long, 2-7 mm. broad, achenes; narrow margined, roots; less than 5 cm. long, thickened and clustered (fascicled).------------ R. fascicularis - (early buttercup)
          1. stems 3-6 dm. tall, 1-few, ascending, declined or trailing, soft and hollow, hirsute; leaves lower ternately compound, long-petioled; sepals hirsute to glabrous, tardily reflexed. 6-10 mm. long; petals rounded-obovate, 7-15 mm. long, 4.5-10 mm. broad; stigma terminating the long style; roots fibrous ----------------------------------------------- R. hispidus Michx. In Iowa, R. hispidus has two varieties var. caricetorum - (bristly buttercup), prefers wet marshy locations. R. hispidus Michx. var. nitidus) which prefers moist woodland habits. R. septentrionalis var. nitidus is a synonym for the second variety.
        1. Petals numerous 5-9 or double flowered
          1. Creeping habit; branches commonly trailing or repent elongate, flowering stems ascending; leaves dark green often mottled with white (variegated);--------------------------------------------- R. repens - (creeping buttercup) [alien]
          2. Upright habit; stem erect, forking 0.1-1.5 m. high, rather firm------------------------------ R. acris - (tall buttercup) [alien]