Take a cutting from a mature Texas sage to grow in a container. Cut off a terminal branch, 4 inches long, after the plant has finished blooming. Strip the bottom 1 inch of leaves.
Fill a pot with a half-and-half mixture of perlite and sphagnum moss. Embed the cutting 1 inch into the potting medium. Water it so that just the top 2 to 3 inches of medium are damp. Place the cutting where temperatures are at least 70 degrees Fahrenheit in bright but indirect light.
Keep the cutting moderately damp for two weeks or until it roots. Then allow it to dry out between watering periods. Gradually introduce the plant to bright, direct light.
Prune the ends of the sage to encourage bushing. If the plant gets too much water or has too much shade, it will get leggy. Cut the pieces back to within 1/4 inch of a growth node from which leaves are growing.
Move the pot or container indoors for the winter if you live in an area where temperatures may dip to below 10 degrees Fahrenheit. Sage plants can survive temperatures as low as 5 degrees if they are in the ground, but container plants are more susceptible to cold because they have little insulation for the roots.