Cut 3- to 5-inch length of newly grown stem at a node, where the stem meets the leaves. Take cuttings in late spring or early in the summer, in the early morning, when herbs grow most actively.
Fill a flower pot with a coarse, well-draining potting mix such as vermiculite or perlite. Water the potting mix until it feels damp.
Place one to three cuttings in one flower pot. Cover the bottom inch with soil and spray a little water around the stems.
Place the flower pot on a south-facing windowsill if possible, to provide as much sunlight as possible.
Cover the pot with a clear plastic bag. Open the bag at the bottom for a few minutes a day, to ventilate the plant. Check the soil regularly and water when the soil is dry to the touch.
Remove the bag when the cutting produces new leaves and roots. Transplant cuttings to their own individual pot.