early spring .. as soon as the ground thaws ... or mid fall ... with warm days and cool nights ...

or .. if it is in the way of progress ... whenever you darn well want to ... with some deep waterings the rest of the summer ...

i would not call the common lilac a foo foo plant.. in fact.. its right up there with all the other 'run it over with the truck plants' ....

if you do it now.. you will probably sacrifice next years flowers.. and it might even die to the ground ... [like the one i moved last august] ... but i doubt you will kill it with just the minimal amount of aftercare ...

so.. there you go.. yes.. no.. and maybe.. lol ..

ken

Thanks Ken,

They are in bloom at the moment; spring has been very late here in the Big Horn mountains of WY.

I'm thinking let them finish blooming and then move and watch carefully.

If you are going to do it now, get a very large rootball and monitor soil moisture closely!