From the notes to the Penguin Book (1959):

"This interesting ballad, not included in the Child compilation, is based on a story that was probably not new when Boccaccio made it famous in the 14th. century.  Hans Sachs put it into verse some two hundred years later, and in the 19th, century, Keats re-wrote it as Isabella and the Pot of Basil.  The English traditional versions are quite unlike Keats, but are very close to Hans Sachs' rendering.  Besides this Hertfordshire version, sets of the ballad have been reported in print from Somerset (Folk Songs from Somerset, ed. C. Sharp, 1904-9; vol.II, p.42, vol.V p.529) and Hampshire (Songs of the Open Road, A.E. Gillington, 1911, p.10).  Mrs. Joiner was unable to remember clearly the beginning of the ballad, and our first two stanzas are from the version obtained by Cecil Sharp from Mrs. Overd of Langport, Somerset, in 1904."  -R.V.W./A.L.L.

This version was collected by Lucy Broadwood, from Mrs. Joiner of Chiswell Green, Hertfordshire, in 1914.

DT #309  Laws M32
@courting @family @murder @brothers @love

Other versions on the DT:

The Bamboo Briar
Bruton Town
The Constant Farmer's Son  (In London there lived a pretty fair maid..)
The Constant Farmer's Son  (Once a rich farmer's daughter, in Limerick Town did dwell...)
In Seaport Town
The Jealous Brothers

See also  The Black Haired Lass, which may or may not be related.

There is a version at Lesley Nelson's  Folk Music  site:
Bruton Town

There is an entry at the Traditional Ballad Index:  The Bramble Briar (The Merchant's Daughter; In Bruton Town)

For two other versions of this ballad, Lord Burling(ton)'s Sister and In Strawberry Town, see the Journal of the Folk-Song Society (vol. II, p.42 and vol. V, pp.123-127).   A collated version in 5/4 time, titled The Murdered Servantman and collected by Dr. Gardiner in 1906-7, was published in The Wanton Seed (ed. Frank Purslow, E.F.D.S. Publications, 1968).

There are broadside copies of the "London" and "Limerick" versions of The Constant Farmer's Son at  Bodleian Library Broadside Ballads:

The Merchant's Daughter and Constant Farmer's Son  printed by J. Pitts, Printer; Toy Warehouse, 6 Great St Andrew Street, Seven Dials, London, between 1819 and 1844.
Constant Farmer's Son  printed by W. Birmingham, 92, Thomas Street, Dublin, c.1867.

There are a number of other broadside copies, which may be found by searching for Merchant's Daughter.

Keats' Isabella and the Pot of Basil and Boccaccio's Isabela and Lorenzo, together with some nice Pre-Raphaelite paintings, may be seen at  The Isabella Project.  The relationships between these and the ballad are discussed in detail in the Folk Song Journal vol.XIX, pp.123-5.

The real Bruton Town (in Somerset) has its own website:  Bruton Town

Malcolm