RANUNCULUS, familiarly known as “buttercup,” or crowfoot, a characteristic type of the botanical order Ranunculaceae. The Lat. name, which means a little frog or tadpole (dim. of rana, frog), was also given to a medicinal plant, which has been identified by some with the crowfoot. The Ranunculi are more or less acrid herbs, sometimes with fleshy root-fibres, or with the base of the stem dilated into a kind of tuber (R. bulbosus). They have tufted or alternate leaves, dilated into a sheath at the base, and very generally, but not universally, deeply divided above. The flowers are solitary, or in loose cymes, and are remarkable for the number and distinctness (freedom from union) of their parts. Thus there are five sepals, as many petals, and numerous spirally arranged stamens and carpels. The petals have a little pit or honey-gland at the base, which is interesting as foreshadowing the more fully developed tubular petals of the nearly allied genera Aconitum and Helleborus. The fruit is a head of “achenes”—dry, one-seeded fruits. The genus contains a large number of species (about 250) and occurs in most temperate countries in the northern and southern hemispheres, extending into arctic and antarctic regions, and appearing on the higher mountains in the tropics. About twenty species are natives of Great Britain. R. acris, R. repens, R. bulbosus, are the common buttercups. R. arvensis, found in cornfields, has smaller pale yellow flowers and the achenes covered with stout spines. R. Lingua, spearwort, and R. Flammula, lesser spearwort, grow in marshes, ditches and wet places. R. Ficaria is the pilewort or lesser celandine, an early spring flower in pastures and waste places, characterized by having heart-shaped entire leaves and clusters of club-shaped roots. The section Batrachium comprises the water-buttercups, denizens of pools and streams, which vary greatly in the character of the foliage according as it is submersed, floating or aerial, and when submersed varying in accordance with the depth and strength of the current. The ranunculus of the florist is a cultivated form of R. asiaticus, a native of the Levant, remarkable for the range of colour of the flowers (yellow to purplish black) and for the regularity with which the stamens and pistils are replaced by petals forming double flowers. R. asiaticus is one of the older florists' flowers, which has sported into numberless varieties, but was formerly held in much greater esteem than it is at the present time. According to the canons of the florists, the flowers, to be perfect, should be of the form of two-thirds of a ball, the outline forming a perfect circle, with the centre close, the petals smooth-edged, the colour dense, and the marking uniform.
The ranunculus requires a strong and moist soil, with a fourth of rotten dung. The soil should be rom 18 in. to 2 ft. deep, and at about 5 in. below the surface there should be placed a stratum 6 or 8 in. thick of two-year-old rotten cow-dung, mixed with earth, the earth above this stratum, where the roots are to be placed, being perfectly free from fresh dung. The tubers are planted in rows 5 or 6 in. apart, and 3 or 4 in. apart in the rows, the turban sorts in October, the more choice varieties in February. They should be so close that the foliage may cover the surface of the bed. The autumn-planted roots must be sheltered from severe frost. The plants when in flower should be screened from hot sunshine with an awning; when the leaves wither, the roots are to be taken up, dried, and stored. The ranunculus is readily propagated from seed obtained from semi-double sorts, which are often of themselves very beautiful flowers. It is generally sown in boxes in autumn or spring. The young plants thus raised flower often in the second, and always in the third year.
The turban varieties, which are very showy for the borders, are of a few positive colours, as scarlet, yellow, brown, carmine, and white. The florists' varieties have been bred from the Persian type, which is more delicate.
Other species known in gardens are R. aconitifolius (white bachelor's buttons), with leaves recalling aconite, and white flowers; the double-flowered form is known in gardens as fair maids of France or fair maids of Kent. A double-flowered form of R. acris is grown under the name yellow bachelor's buttons. R. bulbosus also has a pretty double-flowered variety. Of dwarfer interesting plants there are R. alpestris, 4 in., white; R. gramineus 6 to 10 in., yellow; R. parnassifolius, 6 in., white; and R. rutaefolius, 4 to 6 in., white with orange centre. Of the taller kinds mention may be made of R. cortusaefolius, a fine buttercup, 3–5 ft. high, from Teneriffe, and hardy in the mildest parts of Britain; and R. hyalli, known as the New Zealand water lily. It is a handsome species, 2 to 4 ft. high, with large peltate leaves often a foot in diameter, and with waxy white flowers about 4 in. across. It is not quite hardy, and even under the best conditions is a difficult plant to grow well.