Arborvitae (Thuja occidentalis) is a variably sized evergreen shrub with an upright pyramidal, columnar or rounded form. Hardy in U.S. Department of Agriculture Hardiness Zones 2 through 8, arborvitaes prefer well-drained soil and full-sun locations. Rooting by stem tip cuttings is a recommended method of propagation.
Fill a container with drainage holes with a lightweight potting mix and mist with water until well moistened.
Cut 6-inch long, leafy stem tips from arborvitae stems 1 year old or less. Washington State University extension recommends taking cuttings from the main shoot or from long side branches during the active growing season in spring or summer.
Remove the foliage from the bottom 1 inch of the stem cutting and wound it by cutting a 1 inch line down one or two sides.
Remove a small portion of rooting hormone from the package and roll the wounded stem of the stem cutting in it.
Make a narrow hole in the potting mix to accommodate the cutting. Place the stem cutting into the hole and lightly firm the potting mix around it.
Water the potting mix to settle it around the cutting and cover the container with a bottomless plastic milk jug. The container acts like a miniature greenhouse and helps maintain humidity for the cutting and reduce evaporation.
Place the cuttings away from direct sunlight because the temperature will be too hot for them to tolerate.
Keep the cuttings moist by misting once or twice daily with water. When a slight tug meets resistance, the cuttings have started rooting. Adequate rooting for transplant may take two to three months, according to Washington State University extension.