'tall-flowered' originates from Modern English, specifically as a compound combining the adjective 'tall' and the past-participial adjective-forming element from 'flower' ('flowered'), meaning 'having flowers.'

'flower' derives from Old French 'flor' (or 'flour') and ultimately from Latin 'flos, floris'; the element 'flowered' developed in Middle and Modern English as the adjective 'flowered' (bearing flowers). 'Tall' developed in Middle English to describe height; the compound 'tall-flowered' was formed in Modern English by combining these elements to describe plants.

Initially, 'tall' referred to stature/height and 'flower' referred to a blossom; over time the compound came to mean specifically 'having flowers borne on relatively long stems' or 'producing flowers that stand high above the foliage.'