Answer: Syringa vulgaris, the common lilac, as well most hybrid Japanese and Chinese lilacs can withstand cold winter temperatures. The roots will be most susceptible to winter damage when they are left above ground without protection. You can ensure winter survival if you place the pot in an insulated box (but leave the top of the plant exposed). This will protect the roots from freezing completely and will still give the tops the pronounced winter chill they need to produce flowers.
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