In its modern acceptation, this name may be taken to cover a group of allied forms put under one variable species. Plants have been received at Kew under perhaps a score of different specific names; they differ in certain characters of more or less importance, but still bear a striking resemblance to each other. It has been found impossible to fix on permanent characters that would clearly differentiate them, and they have, in consequence, been all included under G. tinctoria. Many are minor forms of the tall, erect dyer’s greenweed (var. virgata). Others are distinguished by characters defined below.
G. tinctoria (type) – A low, often semi-prostrate shrub with creeping roots, usually only a few inches high in the wild, but up to 2 ft under cultivation. Stems more or less grooved, clothed with simple, dark green leaves that are linear-lanceolate, 1⁄2 to 1 in. long, hairy on the margins. Racemes erect, terminal, each 1 to 3 in. long, produced on the shoots of the year from June to September. Owing to the branching of the stems near the top under cultivation, a crowd of racemes is often produced, forming one large panicle. Flowers 1⁄2 to 3⁄4 in. long, yellow, without hairs; pods 1⁄2 to 3⁄4 in. long, glabrous, carrying eight to twelve seeds.
This typical form is common in the British Isles, especially in poor grassland, and dry gravelly soils. It is also spread over Europe, and reaches Siberia. Under cultivation it is a pretty plant and flowers freely, but is not so attractive as its variety ‘Plena’, which is also a dwarf, semi-prostrate shrub, but owing to the more numerous petals more brilliant in colour. This is, indeed, one of the best of all dwarf yellow-flowered shrubs. Seeds and cuttings can be employed to increase the typical form, but the double-flowered one, being sterile, can only be propagated by cuttings. In former times this genista was of some value as the source of a yellow dye.
Although known as ‘greenweed’, the colour derived from it was a bright yellow, and it was only by afterwards dipping the yellow yam or cloth into a blue solution of woad (Isatis) that the green tint was obtained. This was the process by which was obtained the once celebrated ‘Kendal green’, so-called from the town of Kendal in Westmorland, in the vicinity of which the plant was abundant, and where also the process was first introduced by Flemish emigrants in the reign of Edward III. (Treasury of Botany, Vol. 1, p. 526.)
The varieties given below comprise most of the main variations of G. tinctoria found in Europe, but intermediate forms occur. It is obviously desirable that commercial clones should be given distinctive names, as has been done in the case of ‘Royal Gold’. The variations of G. tinctoria are discussed by P. E. Gibbs in Notes R.B.G. Edin., Vol. 27, pp. 33-37.
var. alpestris Bertol. – Of procumbent habit, with small, narrow leaves and unually glabrous pods. Found in the Alps, Italy, etc. Similar plants occur on sea-coasts (var. litoralis Corbière).
var. anxantica (Ten.) Fiori – This has a similar habit to typical G. tinctoria but is wholly glabrous and the flowers are considerably larger (2⁄3 in. long). It was described from the region of Lanciano in central Italy. Introduced 1818; suitable for the rock garden.
var. humilior (Bertol.) Schneid. G. ovata var. humilior Bertol.; G. perreymondii Loisel.; G. mantica Poll.; G. lasiocarpa Spach, nom. illegit.; G. lasiocarpa var. perreymondii (Loisel.) Spach, comb, illegit.; G. t. var. lasiocarpa (Spach) Gren. & Godr. – This group comprises plants of medium height with downy leaves, stems and pods. S. Europe.
var. ovata (Waldst. & Kit.) F. Schultz G. ovata Waldst. & Kit. – A shrub 2 to 4 ft high. Leaves ovate, elliptic or oblong, up to 1 in. or slightly more long and up to 3⁄4 or 7⁄8 in. wide. Racemes to 3 in. long, flowers densely arranged. Pods hairy. Native mainly of Rumania, N. Yugoslavia, Hungary, and E. Austria. Introduced 1819.
cv. ‘Plena’. See above.
cv. ‘Royal Gold’. – Stems erect. Flowers golden yellow in terminal and axillary racemes, forming a narrow panicle. Ultimate height said to be 2 ft.
var. virgata Koch G. virgata Willd., not Lam., nor (Ait.) Link; G. t. var. elatior (Koch) F. Schultz; G. elatior Koch – In its morphological characters this resembles ordinary G. tinctoria, but is an altogether bigger, stronger-growing shrub. It is of quite erect habit, 3 to 5 ft high, leaves up to 11⁄2 in. or more long, 1⁄4 to 1⁄2 in. wide. Flowers individually no larger than in the common form but borne in larger panicles sometimes 12 to 18 in. high. Native of S.E. and east central Europe. It should not be confused with G. tenera (“G. virgata” of gardens).
G. patula Bieb., described from Russian Armenia, is included in G. tinctoria sens. lat. by P. E. Gibbs in Flora of Turkey, Vol. 3, p. 25. The plant described in previous editions under this name was collected by E. K. Balls in 1934 near Trabzon (Trebizond), Anatolia, where it inhabits limestone cliffs up to 3,000 ft altitude. This form was distinguished by its very slender, strongly grooved stems, narrow leaves, and hairy pods.