Dividing, or cutting, roses is a method used to propagate heirloom roses or roses that were grown on their own rootstock. Roses can be divided at any time during the growing season, when the health of the mother plant can be determined. Although it doesn't take long to cut and prepare the stem from the rose, it can take several years for the stem to develop into a plant with multiple canes.
Select the stem to cut on a healthy rose. Look for a stem that is more than 4 inches long, has recently bloomed and is wider than a pencil's width.
Locate the slightly enlarged swelling where the stem attaches to the larger cane. Make a diagonal cut through the center of that section. Remove the spent blossom and all the leaves, and then place the cut end immediately into a container of warm water.
Fill a clean plant container with sterile potting soil. Dip the cut end of the stem into rooting hormone and insert it into the potting soil, burying half of the stem. Water the soil thoroughly to settle it around the stem.
Invert a 1 gallon jar over the stem. Press the mouth of the jar into the soil in the container to secure its position. This creates a self-watering terrarium.
Carry the terrarium with the rose stem outside. Place it next to a north-facing wall, behind a bush or something that will shield it from direct sunlight.
Inspect the cutting at least once a week. New red leaves are a sign that the cutting has rooted; it can take several months for the rose to reach this state. Leave the cutting in the terrarium until the last freeze date has passed. The rose can then be transplanted to a larger pot or planted directly into the garden.