Lemon verbena (Aloysia triphylla), some small species of perennial shrub, is grown for its slender, aromatic foliage and dainty flower clusters, that include ornamental appeal in the summer. It rises in U.S. Department of Agriculture plant hardiness zones 8 to 10, where it will reach a rise of 1 to 3 feet using an 18-inch spread. Lemon verbena propagates best from semi-hardwood cuttings taken in midsummer, which will root in a couple of weeks — with or without rooting hormone — if kept under warm, humid conditions.
Fill a 4-inch plastic or terra cotta pot using a mixture of equal parts perlite, coarse sand and coir. Saturate the mixture with water and let it drain.
Collect a 4- to 6-inch-long semi-hardwood cutting out of a mature, healthy lemon verbena plant. Pick one with lots of leaf, no busy flowers along with a stem diameter of about 1/4 inch.
Sever the cutting edge 1/16 inch under a set of leaves with sharp pruning shears or a utility blade. Strip off all the leaves out of along the lower one-half of the cutting edge to expose the nodes.
Dust the severed end and exposed nodes using rooting hormone powder to accelerate root manufacturing, if wanted. Apply the powder using a clean cotton swab. Gently tap or visualize the stem to knock off excess powder.
Poke a hole in the center of this perlite mixture. Be sure the hole deep enough to hold the defoliated portion of this lemon verbena stem. Insert the stem and then push the perlite mix snugly against it. Drizzle water around the stem to settle on the mix.
Place the potted lemon verbena cutting within a 1-gallon clear plastic bag. Secure the bag around the underside of the pot using a rubber band. Make a 1-inch cut in the cover of the bag to allow any trapped moisture to escape.
Set the pot on a lightly shaded garden seat outside or indoors on an east-facing windowsill. Warm the pot to 70 degrees Fahrenheit using a propagation mat if daytime temperatures remain below 65 F. Shield the cutting from direct sunlight to keep it from wilting.
Remove the plastic bag every other day and test the moisture level in the perlite mix. Add water when it feels mostly dry under the surface. Mist the lemon verbena cutting with water to keep the leaves hydrated.
Check for roots in three to four weeks by gently pulling the base of the stem. Feel whether the cutting has anchored to the perlite mixture by roots. Remove the plastic bag one week after rooting.
Transplant the lemon verbena into a 4-inch container full of potting soil fourteen days after it roots. Grow it under gently shaded conditions. Acclimate it to direct sunlight within several days in early fall, then transplant it into a permanent bed.