From the notes to the Penguin Book (1959):

"This is one of the most curious, most beautiful, and most widespread of British ballads.  Some fifty years ago, Kidson reported it as "common all over the country", and it is not infrequently met with nowadays, especially in Scotland and Ireland.  Sharp alone collected a dozen sets of it.  Perhaps the fullest printed texts are Scottish, though English and Irish sets include verses not found in Scottish versions.  It is sometimes said that the ballad is based on the actual marriage of the juvenile  laird of Craigton  to a girl several years his senior, the laird dying three years later in 1634.  But in fact the ballad may be older; indeed, there is no clear evidence that it is Scottish in origin.  Child marriages for the consolidation of family fortunes were not unusual in the Middle Ages and in some parts the custom persisted far into the 17th. century.  The presenting and wearing of coloured ribbons, once common in Britain, still plays a prominent part in betrothal and marriage in Central and Eastern Europe.  For some reason this ballad, so common in Britain, is very rare in the U.S.A.  The melody given is in the Phrygian mode, seldom met with in English folk song (a different tune to these words, in Songs of the West, ed. Baring Gould and others, 1896, pp.8-9, is also Phrygian).  Only one stanza of Miss Bidder's version has survived.  The greater part of the text we print comes from the versions sung to Sharp by Harry Richards of Cerry Rivell, Somerset, in 1904 ¹ (FSJ vol.II [issue 6] pp.44-6), and to Lucy Broadwood by Mrs. Joiner, of Chiswell Green, Hertfordshire, in 1914 (FSJ vol.V [issue 19] p.190). In FSJ, further versions will be found from Surrey (vol.I [issue 4] pp.214-15), Somerset (vol.II [issue 6] pp.46-7), Sussex (vol.II [issue 8] p.206), Yorkshire (vol.II [issue 9] p.274) and Dorset (vol.II [issue 9] p.275)."  -R.V.W./A.L.L.

This version was collected by Bertha Bidder from an unnamed woman singer of Stoke Fleming, Devon (date unknown), and was first published in the Folk Song Journal, vol.II [issue 9] p.95.

Other versions on the DT:

Daily Growing     (Bonny Boy Is Young or Trees Grow High, etc.) Original source unknown; presumably transcribed from record(s), with a verse from the Penguin version added.  3 unidentified tunes are given; the second (DAILYGR3) is actually the Penguin version.

My Bonny Boy     Original source unknown; transcribed from a record by Mary O' Hara, no tune given.

Lady Mary Anne  The Robert Burns rewrite, with tune.

In the Forum:

The Bonny Boy  Transcribed from a record by Mary O' Hara, no tune or original source given.

Name that tune   Version possibly from Jeannie Robertson?  No tune given.

DT #307
Laws O35
@love @death @marriage @school

There is an entry at  The Traditional Ballad Index:

A-Growing  (He's Young But He's Daily A-Growing) [Laws O35]

There are three versions at Lesley Nelson's  Folk Music  site:

The Trees They Do Grow High  (Daily Growing) Version 1.  This is the DT text.  With tune; source not specified.

The Trees They Do Grow High, Version 2  Lyrics and Music, described as "a mix from Benjamin Britten's Folksong Arrangements and The International Book of Folk Songs"  ¹ The tune is the version collected by Cecil Sharp from Harry Richards in 1904, transposed to a higher key.

Still Growing  (The Trees They Do Grow High) "Lyrics From Ron Clarke".   Appears to be a collated text.  With tune; source not specified. (Same as "version 1").

Other titles:

The Trees So High
Young but Daily Growing
The Trees They Grow So High (The Bonny Boy)
Young and Growing
My Bonnie Laddie's Young (But He's Growing Yet)
Young Craigston
The College Boy

There are some broadside texts at  Bodleian Library Broadside Ballads,  These are the most legible:

My bonny boy is young but he's growing  Printer and date unknown.

My bonny boy is young but he's growing  Printed between 1840 and 1866 by J. Harkness, of Preston.

My bonny lad is young and growing         Printed between 1858 and 1885 at the "Catnach Press," by W.S. Fortey, 2 & 3, Monmouth Court, Bloomsbury, London.

My bonny lad is young, but he's growing  Printed between 1863 and 1885 by H. Such, Machine Printer & Publisher, 177, Union Street, Boro'., S.E., London.

My bonny lad is young, but he's growing  Printed between 1849 and 1862 at Such's Song Mart, 123, Union Street, Borough, London.

These are large images.

Malcolm