noun
blooming tachibana; tachibana flower
Refers specifically to the flowers of the tachibana (Citrus tachibana), a native Japanese citrus tree. Often used in poetic or seasonal contexts.
See also: 橘
庭に花橘が咲いている。
The tachibana flowers are blooming in the garden.
橘 refers to the tachibana tree or its fruit in general, while 花橘 specifically means the blooming flowers of that tree.
Compound of 花 (hana, 'flower') and 橘 (tachibana, 'tachibana tree'). The exact historical derivation is straightforward.