I have an old lilac bush that I would like to propagate. Suckers work, but I would like more control over amount, uniformity, and size. I had heard that they root readily from hardwood and semi-ripe cuttings, but after several failed attempts, I came here for some help. So, how are these cuttings taken?
From this site
What should be noted is that you need strong shoots that have a little bit of woodier stem and you need the strongest rooting hormone you can get. It used to come in three strengths and I recommend the strongest.
Take cuttings in the spring.
Try various rooting mediums but constant moisture, higher humidity levels and bottom heat are required. The quote recommends an artificial soil-less mix but I would also try floral foam, glasses of water or even pure perlite.
The trick with cuttings is lots of humidity to compensate for the lack of roots, lots of light and air movement to prevent mould. For many this means a greenhouse.
Well I must have gotten lucky because I was doing a clean up pruning of my dwarf lilac in early spring here in zone 4b. I took a cutting that was crossing through the plant and for fun just stuck it deep in the soil next to my other lilac. What do you know? It now has leaves and flower buds and looks pretty happy. No rooting hormone either.