View source for Senecio

{{SPlantbox
|familia=Asteraceae
|genus=Senecio
|lifespan=perennial, annual, biennial
|life_ref=Flora - A Gardener's Encyclopedia
|Temp Metric=°F
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|image=Golden Ragwort Senecio aureus Flowers 2616px.jpg
|image_width=240
}}
'''''Senecio''''' ({{pron-en|sɨˈniːʃi.oʊ}})<ref>''Sunset Western Garden Book,'' 1995:606–607</ref> is a [[genus]] of the daisy [[family (biology)|family]] ([[Asteraceae]]) that includes '''ragworts''' and '''groundsels'''. The flower heads are normally rayed, completely yellow, and the heads are borne in branched clusters. ''Senecio'' is one of the largest genera of [[flowering plant]]s, and despite the separation of many [[species]] into other genera it still contains over 1000 species of varied form, including leaf, stem and tuber succulents, annuals, perennials, aquatics, climbers, shrubs and small trees. Some species produce natural [[biocide]]s (especially [[alkaloid]]s) to deter or even kill animals that would eat them.

''Senecio'' species are used as food plants by the [[larva]]e of some [[Lepidoptera]] species — see [[list of Lepidoptera that feed on Senecio]].

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Senecio (Latin name for plants of this genus, ultimately from senex, "old man;” said to be in allusion to the hoary pappus). Compositae. Groundsel. A various group, some of the herbaceous members of which are grown as border plants for their mostly yellow heads and sometimes for the striking habit; others are climbers, grown mostly indoors, as the so-called German ivy; the shrubby kinds are little known in cultivation.

Senecio is probably the largest genus of plants, comprising some 1,200 species in all parts of the world. A genus comprising so many members and being so widely distributed is necessarily variable and therefore practically impossible of concise definition. A distinguishing mark of the senecios lies in the character of the involucre,—scales or bracts in one series, and usually reinforced at the base by shorter scales or bracteoles that give the head the appearance of having a small calyx. Heads usually radiate, the ray-florets pistillate and fertile, but sometimes the rays absent and then the head is homogamous (florets all of one kind, i. e., perfect); disk-florets tubular, 5-toothed; style-branches subterete, truncate, rounded-obtuse, occasionally terminated by a small penicillate tuft of hairs; receptacle usually naked: achenes mostly terete and ribbed; pappus of soft whitish, often copious bristles. Most of the senecios are yellow-rayed. Of the vast number of species, very few have gained prominence in horticulture.

To Senecio belong the genera known to gardeners as Jacobaea, Kleinia, and Cineraria. The latter is a Senecio, although the florist's cineraria is described under that name in Vol. I of this work. Bentham & Hooker refer to Senecio the genus Cacalia, which is kept distinct by American botanists. Hoffman (in Engler & Prantl’s Naturl. Pflanzenfamilien) refers the garden genus Emilia to Senecio, but keeps Ligularia (including Farfugium) and Cineraria (not the florist’s cineraria) distinct. See Emilia; also Ligularia.
 
If the greenhouse cineraria (which is technically a Senecio as understood by Bentham & Hooker) is omitted, the most popular species are S. mikanioides or German ivy, S. elegans or purple ragwort, S. pulcher, S. Cineraria, one of the plants commonly known as dusty miller. Various other plants are known as dusty miller, and one of them, Artemisia Stelleriana, is sometimes confounded with Senecio Cineraria. Most other species are of very minor importance to the horticulturist. Several species are found in the European trade, and of the sixty or more species native to the United States and Canada, about a half dozen have been offered by dealers in native plants, but they are practically unknown horticulturally. Most of the species are wholly herbaceous, but in South Africa, Australia, Central and South America many species are shrubby. Some species are even arborescent; others are climbers. In South Africa and the Canaries is a small series of species that has been separated as Kleinia, distinguished mostly by their habit, being for the most part fleshy shrubs or herbs, with terete or angular stems and whitish or pale yellow rayless flowers. Species of this group are sometimes seen in collections of succulents. S. vulgaris, Linn., from Europe, is a common annual weed in various parts of this country.
 
Since senecios afford both greenhouse and hardy border plants, it is impossible to give general cultural directions. The species are not difficult to manage, however, and most of them propagate readily by means of greenwood cuttings and seeds; the hardy species may be divided. Most of the tender species require coolhouse conditions. 

Several species which have been described under the genus Senecio, some being of rather recent intro., seem to the writer to be more satisfactorily treated under the genus Ligularia. Among those appearing to be of considerable importance from a horticultural standpoint are the following: Ligularia clivorum, Maxim. (Senecio clivorum, Maxim.). A robust herbaceous perennial, 4 ft. high, at first tawny-pubescent, glabrate: radical lvs. long-petiolate, reniform or subrotund, sometimes 20 in. diam., sharply mucronate-dentate: heads large, many-fld., radiate with orange-yellow rays; disk-fls. dark brown. Japan and China. Flowers Aug. and Sept.—Lingularia macrophylla, DC. (Cineraria macrophylla, Ledeb. —Senecio Ledebourii, Schz. Bip.); for description see p. 1859, Vol. IV.—Senecio Purdomii, Turrill. St. erect, sulcate, densely tawny-pubescent: radical lvs. long-petiolate, broadly orbicular, about 12 in. long, 15 in. broad: infl. paniculate; heads rayless. China. Intro. into England in 1914 by Veitch & Sons. Not yet known in American gardens. Needs further study.—Ligularia stenocephala, Greenm. comb. nov. (Senecio stenocephalus, Maxim. Bull. Acad. St. Petersb. 16:218. 1871. S. cacaliaefolius var. stenocephalus, Franch.). Radical lvs. long-petiolate, reniform, about 9 in. long, 16 in. broad, deeply cordate, coarsely toothed, glabrous on both surfaces: infl. racemose, 12 in. or more long, 2 3/4 in. wide at the base; heads radiate; ray-fls. 1-5, rays yellow; disk-fls. 5-6. China.—Ligularia, Veitchiana, Greenm. comb. nov. (Senecio Veitchianus, Hemsl. G.G. III. 38:212. 1905). A very stout perennial herb with simple flowering st. 3-6 ft. high; radical lvs. 15-16 in. long, 10-11 in. broad, sharply dentate: heads very numerous, about 2 1/2 in. diam.; ray-fls. 10-12, rays yellow. China. G.M. 50:741.—Ligularia Wilsoniana, Greenm. comb. nov. (Senecio Wilsonianus, Hemsl. G.C. III.38:212. 1905). Giant Groundsel. A robust herbaceous perennial with a flowering st. 3-5 ft. high: radical lvs. long-petiolate, the blade reniform-cordate, 10-20 in. long, 9-10 in. broad, sharply dentate: infl. an elongated columnar-like spike, branched at the base; heads very numerous, radiate, about 1 in. diam.; ray-fls. 6-8, rays yellow. China. This and the preceding one are desirable plants for ditch-borders and bog-gardens.
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