We grow herbs to season to our food but also to provide fragrance and texture to our gardens. In some places, herbs are used to compose the entire garden. Propagating these plants depends on how the type of plant and how many of them are needed. If only a few plants are required, a trip to the garden center will suffice but if you want to fill a section of a border with lavender or make pesto with basil, try propagating your own plants.
Propagate annual herbs like basil, dill, cilantro and parsley from seed. Harvest tiny seed from seed heads that develop following the plant's blooms. Make multiple sowings throughout the summer; once an annual blooms and makes seeds, it dies.
Divide some perennials to make new plants and rejuvenate old ones. Dig root balls of plants like anise, chamomile, tarragon and oregano. Cut large clumps into several "crowns" (containing shoots and roots) with a knife. Set them at the same depth as the parent plant in holes lined with enriched soil. Divide plants in spring or fall.
Take stem cuttings in spring from woody perennials. Use "soft" end cuttings with lavender and new wood cuttings with thyme or French tarragon and stem cuttings with lemon verbena and garden sage. Cut 3-4 inches from growing shoots, strip the bottom inch or two of leaves, dip in a rooting hormone powder and plant in peat "plugs" or sterile medium in peat pots.
Layer stems to propagate very woody plants like rosemary. Make a short, angled slice into a growing shoot and brush the wound with some rooting powder. Prop the slice open with a sliver from a toothpick and wrap a bit of damp peat moss around the wound. "Bandage" the peat moss dressing with plastic wrap and wait for roots to begin to show through the plastic. Snip the branch below the cut and plant the shoot.
Plant seed for perennials like fennel that do not transplant well. Propagate by seed in spring to introduce new varieties of perennials but give them a few years to grow before beginning to take divisions.