Complex sentence: Gorse is closely related to the brooms, and like them, has green stems and very small leaves and adapts to dry growing conditions, but differs in its extreme spininess, with the leaves being modified into 1-4 cm long spines.
Split into simpler sentences: Gorse is closely related to the brooms, and like them, has green stems and very small leaves and is adapted to dry growing conditions. However it differs in its extreme spininess, with the leaves being modified into long spines.