"Ornata" wrote
I'm wondering how best to over-winter my dahlias in my London garden.
Last year I dug up the "posh" ones ('Bishop of Llandaff', 'Moonfire'
and seed-grown Dahlia coccinea var palmeri) but left some others in the
ground. In spring all the ones left in the ground came back, whereas I
had a few casualties amongst my stored tubers. I'm tempted to keep the
lot in the ground and cover them with mulch, but my concern is that
they might not survive if we have a wet winter (last year, although we
had a few very cold days, was pretty dry). Or am I behind the times
and do most people in the south of the UK leave their dahlias in the
ground over winter as a matter of course? If not, any tips on how to
prevent the stored ones from rotting?

We leave our plants in, both at home where they are just left and down on
the exposed allotments where we use straw as a mulch.
The only casualty we have had, and we have always left them in, was a
species, Dahlia imperialis, that didn't come up this year although it's been
out for a few before without problems. (A cutting from that survives in a
friends garden and it's now well over 12ft high but still no flowers) I
suspect it was something other than frost that killed it.
The only problem is that if you mulch and don't remember to slug pellet them
in the spring, the slugs, under the mulch, eat the tips as quickly as they
grow so it can seem they haven't survived.

--
Regards
Bob
In Runnymede, 17 miles West of London