'extended-flowering' originates from modern English, specifically a compound of 'extended' and 'flowering', where 'extended' ultimately derives from Latin 'extendere' (ex- 'out' + tendere 'to stretch') and 'flowering' derives via Old French/Old English from Latin 'flōs' meaning 'flower'.

'extended' changed from Middle English 'extenden' (from Old French/Latin 'extendere') and 'flowering' changed from Middle English forms like 'flouring' (from Old French 'florir' and Latin 'flōs'); the phrase 'extended flowering' was later formed in English and sometimes hyphenated as 'extended-flowering' to function adjectivally.

Initially the parts meant 'to stretch out' (extendere) and 'to produce flowers' (florire), and over time the combined phrase evolved to describe the modern meaning 'having a prolonged flowering period'.