You could fill your garden with roses (Rosa spp.) by propagating a tray of cuttings, but that takes a level of diligence -- constant watering and potting up -- that you may not have the time to commit to. Air layering is a propagation technique that lets you create new plants from your favorite roses, and the plant does most of the work for you. Another benefit of air layering over propagation by cutting is that your new rosebush may continue blooming, even as it develops its new roots.
Select a healthy cane, about as big around as a pencil, in early spring that you might otherwise prune away to open up the center of your plant. It should still be green, without woody bark, and have swelling buds with no signs of disease or insect damage.
Strip an 8-inch length, beginning low on the cane, of all leaves and thorns. Thorns generally snap off when you push on them from the side with your gloved thumb. The cane remains on the plant.
Make two shallow cuts -- just breaking through the green outer bark -- all the way around the cane with a sharp, clean knife. The first cut should be 1/4 inch below a leaf node in the stripped area, and the second 1 inch below the first. Peel away the green outer bark of the cane between the two cuts.
Scrape the cut area with the edge of the knife until you reach the white pithy core at the center of the cane. None of the green cambium layer below the bark should remain in the cut area, or roots won't develop. Avoid scraping so much that you go through the cane, you just need to remove all traces of green.
Place a small amount of rooting hormone powder along the upper edge of the cut all the way around the cane.
Gather the bottom edge of a 6-inch-square piece of plastic wrap in your hands and fasten it around the cane, just under the bottom of the cut, with a piece of string, coated wire or plastic zip tie. Do not compress the cane.
Place a handful of damp sphagnum moss over the cut area, wrapping it all the way around the cane. Pull the plastic wrap up over the damp moss, ensuring that the cut ends of the plastic overlap. Fasten the top edge of the plastic wrap around the cane just beyond the top edge of the cut in the same way you fastened the bottom edge. You should now have a little balloon-like packet of damp moss encircling the cane.
Keep the parent plant well watered. Remove the plastic when you see white roots or feel the root mass through the plastic in three to six weeks.
Cut through the cane below the new root ball with sharp, clean bypass pruners.
Cut the newly rooted cane down to no more than 10 inches tall, removing all leaves and side shoots so the fledgling roots have less growth to support.
Plant the cutting in a clean nursery pot filled with moist potting mix. Planting so the root ball is under the soil.
Move the potted plant to an area in bright, indirect sunlight. Keep the soil consistently moist until late fall when the plant prepares for dormancy. Move it to a protected area if you live in an area with cold winters.
Plant your new rose in full sun in late winter to early spring, before it begins to leaf out.