They both should survive the whack. Spread 1-2" compost as mulch & water weekly if no rain. Snowball bush will likely produce a lot of upright shoots as they're sensitive to pruning too much. Spray off the black aphids that appear on the new growth. They seem to get less aphids in part sun & moist soil than when I had them in full sun. Don't fertilize other than the compost as that will promote even more growth, which you don't want. Lilac won't bloom next year. To keep it tidy & get yearly flowers you can prune 1/3 of the branches back to stem each year. Once they're dormant in fall think about moving one of them away to avoid crowding. I've moved our snowball bushes several times & usually in early spring. They've always survived even though they were coming out of dormancy then. I just moved one again this spring & think they're in permanent places now. If not, I know I can move them again despite what I've read in books.

Thanks to the confusion of Common Names, Snowball Bush is used to describe plants from both the Hydrangea and Viburnum Genera. Hydrangea paniculata 'Grandiflora' or PeeGee(P.G.) is sometimes called Snowball Bush, but the most common reference to Snowball Bush is to Viburnum species from China (V. macrocephalum), Japan (V. plicatum) and Europe (V. opulus). If they bloom in the spring, they are Viburnum, since the PeeGee (P.G.) Hydrangea blooms later in summer, July-August. It is interesting to note that most gardeners, some with many years experience, cannot distinguish between the Viburnum & Hydrangea flowers (absent foliage). About the only true distinguishing feature is the number of stamen in each floret, 5 in Viburnum, 7-8+ in Hydrangea. Here is a link that might be useful: Snowball Bush

Assuming it is a viburnum (same common name is applied to a couple of different plants), they can be cut back hard. Anywhere from 8-10 inches, although I'm not sure I'd be quite that aggressive myself. This should be done in late winter or early spring - not now - or if less of a radical approach, immediately after flowering.

purpleinopp, thx for your response. I have always used the intermittent mist propagation technique using coarse sand as my medium. Sand is cheap and the bed and timer takes care of babysitting the cuttings for me. I root large quantities of plants, many, many different kinds and then transfer to pots of soil once they establish a nice root mass. I do this for many reasons: for fun, to "free-scape" parts of my yard, to have plenty of plants to share at plant swaps and hopefully at some point to start selling some at farmers markets, plant yard sales, etc.... I originally started with a nursery bed to put rooted cuttings in but found it to be easier, at least for my needs, to put them directly into pots instead, especially if the end goal is to either give many of them away or sell them. Hardest part is keeping up with summer watering needs since they can dry out quickly. The potting mix I make was based on many suggestions, posts, blogs and websites from other propagators and growers and everything else seems to transfer well to it except for the viburnum. I just read someone else who propagates viburnum uses a commercial potting soil mixed 1/2 with sand. I may try rooting them directly in that and then just up-potting as lyndapaz suggested instead of rooting in the propagation sand box. I may also attempt air and/or ground layering with my large mother plant. As for timing, I prefer to work with soft wood to semi-hardwood cuttings in mid-late spring/early summer on most things and that's typically what I've been rooting from the viburnum. I am less familiar with hardwood cuttings and never tried them much, mostly because of the patience needed for them to root. Perhaps I should give those a shot as well on this one. Danielle