English Lavender is not really a native plant, so it doesn't grow happily just anywhere. If your location meets these requirements, your plants should thrive:
Lavender is a Mediterranean plant. It needs full sun for most of the day to look its best.
2. Free Draining Soil
Lavender hates damp soil.
Establishing Lavender plants must be watered in dry weather, though: soak the soil every 3 days in summer if there is no rain.
3. Air Circulation
Lavender grows best out in the open, with the wind in its hair, not crowded by lots of other, taller plants. It is very wind resistant.
4. Regular Clipping
Lavender should be clipped hard every autumn and can be trimmed lightly once in spring.
This will keep the plants looking young, densely bushy and producing lots of flowers.
Read more about planting lavender here.