I want to take mum cuttings, cut them to length, and then store them in a cooler for 3-4 weeks prior to sticking them in my propagating medium. I know I can dip the cuttings into the powder prior to bagging and storing them. My question is: How long can I effectively store them in the cooler? I have received unrooted cuttings that have been dipped into a rooting powder. I just would like to know how long the rooting powder would be effective in storage.
I should have also said that I will be using small plastic bags to store the cuttings in the cooler.
Like you, I have gotten unrooted mum cuttings that have been dipped and shipped to me but it is likely they were cut no more than 10 days before they arrive. The issue is not how long the hormone will stay effective, but what condition the plant material will be in after a month in storage. To accomplish your goal, I would consider two options.
1) Cut and dip the mum stems and put slightly damp perlite (only perlite, no potting soil) into the plastic bag. The perlite will help to maintain the condition of the cuttings and if they try to root, they can.
2) Take cuttings slightly longer than you want to root, pack and transport them. When you take them out of storage, make a new cut and apply Hormex right before you stick the cuttings.
Whichever way you do this project, you might also consider Hormex Liquid Concentrate as a dip or re-dip right before you stick the cuttings.