hi Giles,
Do you get a lot of rain where you live?
I started growing DL's this year so I'm certainly no expert
But when temperatures were in the 70's I watered my DL's every other day..
and when temps were over 83-84F (which doesn't happen often
) I watered for an hour
As I understand it water is even more essential than fertilizer (during the summer)
Mayo
