Lavender Growing from seeds can take differing times depending on their growing conditions. If the seeds are being grown indoors under lights, then it can take up to a couple of weeks for them to germinate. Once the seedlings get to about 10cm under the lights, they can be transplanted in spring outdoors into sunny, well-draining areas.
Many plants will bloom the second year from seedlings. It takes a few years to actually get the bushy look (depending upon the type that you grow). Lavender can also be purchased in small pots to replant in public areas and can still look fabulous until November. If you have the right growing conditions, they will thrive either way, from seed or purchased plant. It is easier to buy the plants, as the germination percentages vary with starting lavender seeds.