Sacha wrote in :

Can't improve on that! I'd put it back into its last pot, in fresh
compost, as Jake suggests, and water sparingly now that winter is
here.
If you do have to water, it's better to do so in the morning, rather
than having pots stand about wet, all through the night. But
definitely, do ensure good drainage. Yours is an example of why
plants get potted on gradually, something often asked on here. Too
much wet compost 'drowns' them.



Thanks to you both. This is educational for me as I'm no gardening expert.
I took your advice and repotted back to the previous pot. I used some
compost mixed 50/50 with some sand and gravel which was surplus from a
concretete-making project.

When I removed the shrups from the large planters, the roots didn't seem at
all waterlogged. They looked like my idea of optimally moist. I couldn't
squeese any water out of the compost using my fingers. Anyway, there was a
period of a couple of weeks when they could have been waterlogged. After I
copiously watered them, it did rain off and on, for about a week. I wonder
if that was the cause.

I did not have any gravel or stones in the bottom of the pot. Perhaps I
should have included them to improve drainage.

The older (smaller) pots have castellations on the bottom, to prevent the
'standing in water' issue that you mentioned. I hope this does the trick.
I'll keep my fingers crossed!

Thanks again,

Al