division or separation
- Lavender is most easily propagated by cuttings or division. Named varieties of lavender should be propagated by cuttings or layering and not by seed which will most likely not come true. May self-seed if not deadheaded.
Cuttings of strong growth taken with a heel in July or August can be grown in a greenhouse or cold frame the first winter and planting out the next spring after frost danger.
Seeds germinate slowly. Barely cover seeds with soil in a greenhouse. They will germinate in 1 to 3 months. When large enough to handle, put seedlings in individual pots and grow in a greenhouse or cold frame for their first winter, planting them out late the next spring after the last expected frost.
Layering is possible at any time of the year by scraping the bark near the base of a long stem, applying a rooting hormone and bending the stem down and pegging with a "V" cut from a coat hanger.
Deadheading after first bloom may encourage plants to rebloom. This is also a good time to shape plants. But avoid pruning after late summer until new growth begins the following spring. Cut back heavily (to about 6 inches) every 2 or 3 years to keep plants from getting straggly.
Compared with other shrubs, lavender is not a long-lived plant, so it is best to replace old plants about every ten years.
For low hedges there are many dwarf and semi-dwarf cultivars to choose from that respond well to trimming.
More growing information: How to Grow Perennials