What is the best size and the best timing to move lilac suckers? My daughter just bought a house and wants a sucker from an old lilac bush of ours - one of the S. vulgaris, dark single blooms, don't know the name as it was here when we moved in years ago.

Any special tricks to keeping it going?

I think they are pretty tough. My parents dug one for me in the middle of summer and it survived just fine and started blooming about 3 years after planting in my garden.

I think you could get away with it now if she kept it well watered through the summer or wait until fall and it would suffer less shock. Hopefully someone with better knowledge will chime in.