Answer: There are several ways of propagating lilacs. The easiest way is to dig some of the suckers that appear at the base of the plant. Suckers are shoots that grow from the roots of the original plant and form their own roots quite easily. After digging and separating them from the parent plant you can pot them up or plant them in the ground.
Taking a softwood cutting of new growth that is not yet firm is a common propagation method that works for many plants. Cuttings should be about two inches long, with two-three pairs of leaves at the top of the stem. Insert the cuttings into a soilless mix, just up to the lowest leaves. Rooting hormone may be used, but is not essential. It helps to pinch off the growing tip, which helps force more roots. If possible, place the cuttings in a covered environment (a mini greenhouse) and provide bottom heat. Although it's not always possible to get new growth cuttings in November.
Here's another similar method. Semi-ripe cuttings are taken in mid- to late-summer from the current season's growth that has begun to firm. The cutting's base should be quite hard, while the tip should be growing and still soft. Use 2 1/2 - 4 inches, and remove side shoots. Make a shallow wound on the stem by cutting away a thin piece of bark (1/2 inch long). This stimulates rooting. Dip in a rooting hormones and insert in a soilless potting mix. Provide a humid environment.
Hope your 70-year old plant supplies you with lots of new plants!
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