As a spring-blooming flower, fall is the ideal time to propagate lavender. It can, however, be propagated in early spring, before the plant blossoms.
Dividing is not the accepted method for propagating lavender. Lavender will often send down roots from lower branches that touch the ground. You can cut these roots and plant them in another location.
When transplanting the lavender cuttings, take weather and temperature into consideration. While it is important to transplant cuttings in early spring, wait until there is a stretch of several rainy days in the forecast.