Aloysia triphylla, or lemon verbena, reaches a respectable 10 to 15 feet tall in its native Chile and Peru. The large tender perennial may grow as much as five feet in a single season, and is easily killed by frost. But cooks everywhere have discovered the joy of keeping smaller specimens warm and happy on kitchen windowsills year round. Lemon verbena propagates readily from softwood cuttings taken in late spring or early summer.
Choose a healthy, mature lemon verbena plant that you'd like to take your propagation cutting from. This cutting will grow to be an exact clone of the parent plant, so pick one that you like.
Use a clean, sharp knife to remove an unblemished 3- to 5-inch softwood stem tip from an attractive lemon verbena plant. Make a 45-degree cut about ½ inch below a leaf node. The best time to do this is early in the morning during late spring or early summer when the plant is actively growing. This is the time of year that stem tips carry the highest concentration of plant hormones.
Combine equal parts peat moss and Vermiculite and fill a 3-inch pot to within ½ inch of the rim with the mixture. Set it in a shallow container of warm water until the surface of the mix feels moist. Remove the pot from the water and allow it to drain freely for about 2 hours.
Cut all foliage, buds and blooms from the lower half of the lemon verbena cutting. Moisten the bottom ½ inch of the stem with water and dip it into powdered rooting hormone, if you wish. Plant it about an inch deep in the prepared pot.
Seal the potted cutting in a clear plastic bag and poke some holes in it with a toothpick to allow for air circulation. Place it in a warm, brightly lit spot out of direct sun. The top of your refrigerator or above a hot water heater are good choices. Your lemon verbena cutting will root within a few weeks.
Open the plastic bag and check the soil every day to make sure that it never dries out. It should remain evenly moist, but never soggy or wet. Inspect the cutting carefully for signs of new growth.
Remove the plastic bag for good when new leaves begin to emerge. Move it to a bright windowsill out of direct sun.
Plant the lemon verbena in the garden after it has sprouted 4 to 6 new leaves.