I'm an estate gardener and take lots of cuttings throughout the year... I have found that if you can provide a little bottom heat to the containers it will help and also I always water with a weak solution of organic fertilizer once they have started to grow and it works wonders. It has been great fun over the last 5 winters to experiment with cuttings from different plants and watching how quickly some take off compared to others! - Dawn Trainor-Green -
We know Dawn has acres of garden to manage and a greenhouse that must be fully utilized to fill all the beds with special plants. (She's also one of our Forum Moderators.)
We asked: Do you also have supplemental light on the cuttings, Dawn? At our school, when we stuck cuttings for winter classes we would use our three-tier light rack this way: The top fluorescent fixture lowered to just inches above the cuttings. The light for the next shelf below moved all the way up on its track until the cuttings' shelf prevented it moving further. Thus the cuttings were sitting right on top of that fixture's warm ballast. In a cold room (heat down except at class time), lit 24/7, with warm butts, rosemary would root in 2 weeks!
Yes, I have supplemental lighting - we use 1000 watt high pressure sodium lights. They generate lots of heat - they have to be a distance away so they don't cook the plants! Also have thermostat regulated heat mats (24" x 48") so I can adjust heat when I am starting seeds of different varieties and growing preferences. - Dawn -
One way to get bottom heat: The ballast of our fluorescent light fixture is warm. Seeds not yet sprouted and dormant woody cuttings can sit on top of the light until they show green and need light.
More about cuttings in the notes from our Propagation Workshop.