I am trying to grow roses from cuttings. They are sprouting little leaves but are still under empty soda containers for humidity. When I took a few out of the containers, they promptly shriveled up and died. Should I leave them for another month? I don’t want to tug to see if they have roots, as that will disturb them. Do I apply foliar fertilizer?
I have listed a few useful webpages about propagating roses from cuttings below.
To answer your question about leaving them under cover, I think you probably should leave them for at least a brief while, given the very cold weather. I don’t think you need to apply foliar fertilizer at this stage. The resources below should offer some additional advice on caring for your cuttings.
John Fisher’s book, The Companion to Roses (Salem House Publishers, 1986), says that roses grown from cuttings may take longer to flower than those budded on rootstock, but (if they survive the process) they may live longer and will not sucker. Some roses are easier to propagate from cuttings, such as ramblers and Rosa rugosa, as well as some climbing roses and large-flowered roses.
According to Fisher, cuttings can be taken as early as August. You should choose young shoots with ripened wood that have borne flowers, and lateral shoots rather than leaders. He recommends selecting those shoots growing low on the shady side of the plant, and those with leaf joints that are close together. Make a clean cut just below a leaf joint. The cutting should be about 9 inches long with 2 leaf joints in the top 3 inches. Cut off the tip that has borne the flower and the leaf immediately underneath it. Remove leaves (but not buds) on the lower 2/3 of the cutting, since this is the part that will be planted in the ground. The soil should be a mix of loam and sand mixed down to a depth of about 9 inches, in a pot or V-shaped trench. Before planting the cutting, poke a hole in the soil for it to go into. Moisten the bottom end of the cutting with a cotton ball, and dip it in rooting hormone (or willow water). Put the cutting in the soil and press the soil around it firmly. If you need to protect it from frost, cover it with leaves or sacking during the winter. By summer, it should have formed a root, and should be ready to plant in the fall.
The information below may differ somewhat from these directions, but you may get a general sense of how your methods compare, and whether you want to try any of the methods suggested.