The plant in the picture is not lavender. Post a closer picture here or, better still, in the Name That Plant Forum to get an accurate id and then you can get appropriate advice.

Almost looks like some sort of salvia, but it's a bit far away to tell, if the foliage is minty smelling then definitely not salvia.

It's definitely not lavender. Pretty sure that's royal candles speedwell, a type of veronica spicata. It flops over when it gets too tall. The trick is to cut it back once or twice in late spring, maybe to about 6 inches, before it really begins to bloom. That keeps it shorter and minimizes the flopping. You can also divide them in fall and spring every couple of years to keep their size in check.