I just planted 4 Rose of Sharon in the landscape project I did last week. They are hardy in Zone 5 and are blooming right now. They are large, beautiful, do well in full sun, handle heavy pruning very well, transplant very well (I have moved mine at least 3 times), have little to no bug problems, are drought tolerant, come a wide variety of colors and do very well as screening plants.

They do sucker some what but if you plan to use them as a large shrub then they are just the right plant. You can limb them up as a multi-stemmed small tree (I have seem them done that way and they are quite attractive).

The new blue and violet satin colors are wonderful. Check out Monrovia's website for some of the colors. www.monrovia.com and search for rose of sharon or hibiscus syriacus. They look like a Hibiscus but are cold hardy.

I would make sure you add a good soil amendment where you removed the lilac something such as mushroom compost and topsoil. Mix it up good to make sure you've gotten rid of any ant residue. Next spring, fertilize the plant and make sure it has good water.