There are many different kinds of lavender, so that can have a bearing on appearance. Some types are just woodier than others. The spreading habit you note is generally common to older plants that have not been pruned as diligently as is recommended. Typically, these inexpensive plants are replaced on a relatively short cycle as they just don't retain their neat and tidy good looks for more than just a few years. Commercial lavender farms here rotate their crops out on a 3-5 year basis.

yes.. probably differing cultivars.. named varieties ...

did you cut it back this last year ... i think i see a lot of wood in there ... my first thought when things get unruly ... is that i probably did not cut it back properly ... perhaps you werent aggressive enough in how much you cut it back ...

i gave up on Ls in my z5 MI years ago ... extremely short lived plants.. as gal notes ... some times its easier to cut bait and run ...

so the bottom line is.. if its not pleasing you.. move on ..

ken

The lavender looks normal to me for a plant which may not have been sheared over last time it flowered. Not not cut back severely, just sheared a few inches into the current year's growth. When it has finished blooming this year I would clip it over with the garden shears and see if it thickens up a bit.

Maybe I didn't cut it back enough in the spring because I just cut off the growth that was standing up really high. When I cut it back, should I cut all the green and leave just the brown or leave a little bit of green?

I don't think the term 'cut it back' is helpful because it implies something more drastic than you need for Lavender. Just shear over the surface of the green foliage taking it back a couple of inches. Basically treat it like a hedge, not a shrub. And do it after flowering, not in the spring. It is because this wasn't done in previous years that the plant has got a bit lax.