Many thanks for all the detailed replies! I freely admit to knowing very little about plants, but I can follow good advice, of which there's quite a bit here. If I understand you all...

They don't need feed or water over winter. I should have switched to a high potash feed mid-summer, but can still give it a shot now. I should also have cut them back a bit to harden (oops, was letting them grow to fill the space a bit) and mulch on the surface will aid water retention & keep frost away. Oh, and watering is best done slowly rather than a minute's blast with a watering can (oops again). Good thing mother nature's been around longer than I have.

Thanks again,

Roy.