The beauty of salvia is quickly seen when it blooms long stalks of purple flowers and fills any full sun area with long, colorful and dramatic stems. Hardy from zones 3 to 8, in warm climates with mild winters the salvia may grow year round, while in areas with cool winters the plant will die back and grow again when temperatures warm. Luckily, salvia is as good at propagating as it is at blooming in the heat of summer, so propagating salvia from stem cuttings is an easy task which takes less than two months.
Take a cutting of salvia from a stem anywhere from 4 to 8 inches long. Cut the base of your stem from the plant just before a set of leaves with a clean horizontal cut using a sharp knife or pruners.
Place the cutting in a glass and add 2 inches of water to the glass. Place the glass in a sunny area in your home, but out of direct sunlight. Allow the cutting to form 1/2-inch long roots over the next two to three weeks, adding more water when needed to keep it 2 inches deep.
Fill a 4-inch pot with clean potting soil. Cut the top off a clear soda bottle along the top edge of its label. Remove the label, and rinse out the inside of the bottle with water.
Plant the cutting 2 inches deep in the potting soil, and water enough to dampen the soil evenly. Place the soda bottle upside-down in the potting soil to form a miniature greenhouse over the cutting, with the cut edges of the bottle nestled in the soil.
Place the pot where you had been keeping the cutting before, and leave it for two weeks, watering as necessary. Remove the soda bottle after two weeks, and move the cutting to a sunny location indoors. Let the cutting grow in the pot for at least two more weeks, watering when needed, before planting outside.