In article ,
Jaques d'Alltrades wrote:

Water profusely. (Your vine should be planted outside the greenhouse,
BTW, and be guided in, using something soft or which will push aside as
the stem grows in diameter.)

Having watered profusely, water it again.

Interesting that the opposite often applies when growing grapes for
wine-making, in Europe at least. IIRC, irrigation is not allowed if the
vines are to be used for a "quality" wine (eg. Appellation Controlle or
VDQS as opposed to Vin de Pays or Vin de Table, in France) with a few
rare exceptions (experimental vineyards being one).

I wonder if it's something to do with limited yields?

James