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A group of hybrid brooms derived from C. purgans crossed with multiflorus, of which the typical and original clone should be known as C. × praecox ‘Warminster’. This broom has the habit of C. multiflorus, but with denser and heavier masses of young branches. Leaves mostly simple, about 1⁄2 in. long, silky like the young shoots; soon falling. Flowers sulphur-yellow, produced in remarkable abundance in early May, and very beautiful then; but they have a heavy, rather unpleasant odour which renders the plant unsuitable for growing in large masses near the house. It ripens good seed, but the plants do not come true, reverting more or less to one or other parent. It can be increased easily from cuttings placed in sandy soil under cloches or in a cold frame during August. This fine broom first appeared among some seedlings of C. purgans in the nursery of Messrs Wheeler of Warminster about 1867. From its appearance it was surmised that it was a hybrid between that species and C. multiflorus, made through insect agency. The reversion of its seedlings to the white broom have since proved this to be true.
‘Warminster’ sets fertile seed, from which some named varieties have been raised. ‘Allgold’, of Dutch origin, has deep yellow flowers and is slightly taller than the parent; ‘Gold Spear’, raised in Germany in 1955 by G. Arends and first introduced to Britain in 1964, will probably prove to be rather smaller in habit than ‘Warminster’ of which, too, it is a seedling. The flowers are bright yellow, freely borne. In the older ‘Albus’, raised at the Daisy Hill nursery, they are white. For the use of the Warminster broom in recent hybridising, see the introductory note to Cytisus.
The authorship of the name C. × praecox is strictly Wheeler ex Bean, since it was a catalogue name only until W. J. Bean described this broom.
The size of typical C. × praecox (‘Warminster’) was not given in the description. It is 5 to 6 ft in height and quite as much in width. Another clone in this group is ‘Gold Spear’, also known as ‘Canary Bird’, with flowers rather deeper yellow than in ‘Allgold’. It was raised in Germany.