What you are attempting is not easy. The Reference Manual of Woody Plant Propagation, by Micheal Dirr, spends several pages on this one species. See if your library has it, or can get it for you. Al

I thank you for the info. I like the Library very much but when it comes to reference books I would rather be the owner of it, so the reference is there for me anytime I need it. So I just bought it on eBay for 17.00. Thank you again.

Common Lilac is very difficult. I had a zero percent success rate on about 20 cuttings last year. In the same batch I had about a 90% success rate with Hydrangea and Dwarf Korean Lilac.

I would really like to be able to propagate these. Guess my last resort. Invest in better equipment.

The fact that you're asking at this time of year may not indicate that you're trying now, but that should be mentioned. When are you trying?

Is your mama plant making any suckers? They can usually be excavated with some roots.

Have you tried layering (bending a branch to the ground or pot of soil, securing with a rock/brick/anything to hold it in contact with the soil?)

No I'm not trying this now. I tried it around the 2nd or 3rd week in May. i'm in zone 5 but real close to zone 4. I maybe should of waited. Didn't realize we was going to have such a long cold time this spring. Done a lot more reading and I'll be trying next spring with some bottom heat . Yes the mama plant is making suckers. No it don't look like they can be dug up with some roots due to all the older growth and on top of all that the mama plant as you put it is on somebody else's property. so digging and layering is more than likely out of the question.

Is it along the property line? Technically the pieces hanging over are yours but technicalities don't make great neighbor-relationships. If you ask if you could bend a branch to a pot in your yard, only a mean person would say no. Trying cuttings a little later sounds like a good idea. Had some trouble with cooler than usual temps and flooding this summer here too. You're right, that's not helpful for gardening at all unless you're trying to establish a swamp.

No it's not along a property line. The owner of the lilac lives about 3/4 of mile away. I pass by it whenever I go to town. It's a deep purple and for the first time in 5 years I got get the nerve up to ask if I could get some cutting from it. He said, "Sure" I got quite a few but not a one made it. I hate to ask again. But I will.