This well-known shrub is one of the most popular of greenhouse plants and small plants are common in florists’ shops and are even sold in the streets from hawkers’ barrows. It is only in the mildest parts of our islands that it can be grown out-of-doors, but where it thrives it is a very handsome plant. Nowhere, perhaps, did it succeed better than at Ludgvan Rectory near Penzance, but the gardens of S. Devon and Cornwall generally also grow it well. In these places it commences to bloom about the New Year and continues for several months.
It is an evergreen that gets to be 10 to 20 ft high, very leafy and luxuriant in habit. Its young shoots are hairy and somewhat ribbed. Leaves composed of three obovate leaflets 1⁄3 to 3⁄4 in. long, mostly rounded at the end, wedge-shaped at the base; they are scarcely stalked themselves but are borne on a common stalk about 1⁄4 in. long; dark green and glabrous above and covered with silky appressed down beneath. Flowers in slender racemes 2 to 4 in. long, the main-stalk downy. Corolla of the usual pea-flowered shape, rich glowing yellow, about 1⁄2 in. long. Calyx with five awl-shaped lobes, two larger than the others, all glistening with down; flower-stalk 1⁄12 in. long.
The plant described above is representative of the “C. racemosus” of gardens and is believed to be a hybrid between C. stenopetalus and C. canariensis, for which the correct name is C. × spachianus (see further in note on p. 829). It has been in cultivation since before the middle of last century and is sometimes erroneously known as “Genista fragrans” and “Cytisus fragrans”, both of which names are synonymous with C. supranubius.
cv. ‘Everestianus’. – Flowers deeper coloured and habit dwarfer. Raised before 1862 and figured in Rev. Hort., 1873, p. 390.
C. ‘Elegans’. – The origin and status of this broom is uncertain, but it is usually considered to be a form of C. × spachianus. It is very distinct in its greyer, larger foliage (the leaflets being up to 11⁄2 or 2 in. long) and in the stronger growth. The individual flowers are also larger. A very beautiful shrub, in some respects finer than C. × spachianus. It flowers over a long season in spring. Being very difficult to increase by cuttings and not coming true from seed, it has to be grafted on C. × spachianus.
The two species mentioned above as the parents of C. × spachianus may be shortly described here:
C. stenopetalus (Webb) Christ Teline stenopetala Webb; C. maderensis sensu Briq., in part. – This species resembles C. × spachianus but differs in its larger leaflets (up to 11⁄2 in. long), on longer petioles. The var. magnifoliosus O. Kuntze merely represents the extreme of the variation of the species in size of leaf and is scarcely worth distinguishing. Bot. Mag., n.s., t. 327.
C. stenopetalus is allied to C. maderensis but differs in its indumentum of silvery grey (not rusty) hairs. Native of the Canary Islands on the islands of Palma, Gomera and Hierro; it has also been collected on Teneriffe but appears to be rare there.
C. canariensis (L.) O. Kuntze Genista canariensis L. – This species differs from C. stenopetalus and from C. × spachianus in its very short-stalked to almost sessile leaves and its short, dense racemes of bright yellow flowers. In var. ramosissimus (Poir.) Briq. the leaflets are very small, the racemes shorter and more numerous; this variety is also, like C. × spachianus, grown as a pot plant, often as “Genista fragrans”. Native of the Canary Islands.
Mrs Dingwall and Dr Gibbs of St Andrew’s University, who are studying this group of Cytisus, find that C. spachianus is intermediate between C. canariensis and C. stenopetalus and may be a hybrid between them. That the C. racemosus of gardens is a hybrid between these two species was suggested as long ago as 1888 (Rolfe in Gard. Chron., April 23, 1888) and is very probable.
C. × spachianus was described by P. B. Webb in 1845 (Bot. Mag., t. 4195) from a plant raised in the Jardin du Roi, Paris, from seeds he had collected ten years earlier in the mountains of N.W. Teneriffe; he also sent seeds to Young and Penny, who had a nursery near his home at Godalming, Surrey. Of the two parents of C. × spachianus, C. canariensis is fairly common on Teneriffe. There are no old collections from this island in the Kew Herbarium either of C. stenopetalus or of C. × spachianus but there is evidence that both are, or were until recently, to be found there. Both were growing in the late Dr Perez’s garden, Villa Oratava, Teneriffe, in 1911 and 1913, and there is a note from Dr Perez with specimens in the Kew Herbarium to the effect that C. × spachianus was said to have been introduced to the garden ‘from near the forest of Agua Garcia, above Tacoronte, where two or three wild plants still exist’. The plants of C. stenopetalus in Dr Perez’s garden originated from La Palma but also from Teneriffe. ‘in heather earth brought from Agua Mansa (above Orotava)’. There is a specimen of C. stenopetalus in the Kew Herbarium collected by Eric Asplund in 1933 in the Orotava Valley, Teneriffe, at 800 metres, in the Barranco San Antonio.
The name C. racemosus was published by Marnock in 1837 (Floricult. Mag., Vol. 2, p. 37 and t. 19). The figure shows a plant that closely resembles a large-leaved form of C. stenopetalus .It is not the C. racemosus of Nicholson and of gardens, which is C. stenopetalus × canariensis, i.e. C. × spachianus.