|I would like to know if I can start a cutting from the California Lilac.|
You can, indeed, take cuttings of your California Lilac (Ceanothus) to increase your stock of plants. Semi-ripe wood responds best and this is the right time of year to take them. Carefully pull away a healthy sideshoot of the current season's growth so that it comes away with a sliver, or "heel" of bark from the parent shoot. The sideshoot should be about 4" long. Natural rooting hormones will be concentrated in the "heel", but you can help insure success by dipping the end of the cutting in rooting hormone. Place each cutting in a tray or small pot of moistened potting soil and drape plastic over the cuttings to make a tent which will help hold in moisture. Remove the tent for a few minutes every day to allow fresh air to reach your cuttings, then replace the plastic tent. You'll know your cuttings have rooted when new growth begins and the cuttings show some resistance when you try to gently pull them up. After a substantial root system has developed you can repot your new little plants and place them in an area protected from hot afternoon sun. When they growing well (10-16 weeks) you can plant them in the garden. Good luck with your project!