Whilst I am at it. I have dug up a giant clump of day Lilly this morning -
five /six feet diameter ( a bright orange double flower ,not the usual naff
single flower).

I am not particularly a lover day Lilly. This was totally in the wrong
place and I have put me a new greenhouse just behind it. The thing had to
go.

What size would be good to chop it up into for possible transplant?

Can I shove them in the garden now and will they keep going? How about
potting them as a temporary measure?
Currently it and a few satellites which came out separately are sitting
bare rooted ( or whatever) on the garden.

How do I ensure I kill anything left behind where it has come from?