The lyrics are in the DT, and in thread 52326 (The Land o' the leal')
but the author of this composed song is not mentioned.
Jean Elliot (1727-1805).

The song evolved from a discussion about Flodden between her and her brother, as they were riding home in a carriage to Minto House, the family seat, and their memory of an old refrain, "The Flowers of the Forest are a' wede awae."

From R. Borland, 1890, "Yarrow: It's Poets and Poetry,: Thomas Fraser, Dalbeatie.