How to Grow Rosemary From a Cutting in 6 Steps

1. Use sharp scissors to take cuttings. Find a mature rosemary plant and snip the stem five to six inches from the tip, making sure your cuttings come from the soft, flexible new branches. Cut extra stems as backups in case some fail to grow.
2. Remove the lower leaves. Delicately strip off the needles from the bottom two-thirds of the cutting.
3. Place cuttings in a jar of water. Move the jar to a warm area that receives indirect sunlight. Every two to three days, replace the old water with fresh water. Root growth should occur within a few weeks, but it could take longer in cooler temperatures. If any cuttings shed needles and turn brown, that means those cuttings didn’t survive, and you can stop waiting for their roots to grow. When roots develop around the base of healthy cuttings, they’re ready to be planted.
4. Plant each stem cutting in a small container. A sandy soil mix with good drainage is ideal. When planting, avoid damaging the roots by carefully placing each cutting into a three-inch hole in the potting soil. Gently fill in the hole with soil, and water enough to moisten the soil.
5. Care for the potted rosemary plants. Make sure each plant receives indirect light, and water them whenever the surface soil dries out. Once you notice new growth, give the cutting a gentle tug; if you feel resistance, that means it has rooted and is ready for transplanting.
6. Transplant rosemary outdoors. Move your rosemary plants to a larger container or your garden bed. Place them into compost-rich soil with good drainage. Choose a location where they receive six to eight hours of direct sunlight a day.

Source: https://www.masterclass.com/articles/how-to-grow-and-care-for-rosemary#how-to-grow-rosemary-from-a-cutting-in-6-steps