Hi Stower. What you sing is a lot like the Carthy / Joiner version, except that you only repeat the word 'Growing' once, instead of twice.

Carthy's 'Trees'

Here's the Joiner tune, in Lucy Broadwood's hand, from The Full English (click on thumbnail for image). If that is indeed Martin's source then he has spun out the first long note in the refrain for an additional bar.

Mrs Joiner's 'Trees'

I've now been through all of the English tunes in Full English - a cursory search, not definitive by any menas - and I can tell you that, although there are lots of variants to more or less the same tune (although it moves between dorian, mixolydian and ionian modes), very few of them have a refrain of any kind, and sometimes that's just a repeat of the last line. There's one tune from Frank Kidson's MS that looks like it might have the 'Growing... Growing' refrain, but there are no words set to it as far as I can find. Oh hang on, I've found it in the Folk Song Society Journal for 1906 with the words, and it's not that refrain. Interesting one, though. In fact there are all kinds of good ' alternative' versions of the song out there if you go looking.

Thanks, Jack, for the abc of the descending tune. I can't see anything like that in Full English either - in fact what it looks like is an altered version of the Joiner tune. If I had to guess I'd say that it's a revival adaptation, possibly deliberate, possibly not.