Botanical name: Laburnocytisus Adamii
Common names: Adam's Laburnum, Broom Laburnum
Family: Fabaceae
Subfamily: Faboideae
USDA Plant Hardiness Zone Map
Laburnocytisus 'Adamii' is a horticultural curiosity; a small tree which is a graft-chimaera between two species, a Laburnum anagyroides, and a Chamaecytisus purpureus (syn. Cytisus purpureus), which bears some shoots typical of the one species, some of the other, and some which are a peculiar mixture of both 'parents'. The plus sign (+) indicates the generic name is made for a graft-chimaera.
Link to this plant:
https://toptropicals.com/catalog/uid/laburnocytisus_adamii.htm