I am no expert on this but this lavender ( now called Angustifolia I believe) does grow very big and straggly in this sort of way. I don't think you have done anything wrong apart from buying , perhaps, this kind of lavender.

A couple of years ago I planted Lavender Munstead as a short hedge and in terms of tidiness and neatness of growth it is the best one I have had.

Hi there,

Looks like my lavender, all higgle de piggle de, but then I like that.

Did you plant it last year?

Maybe it was all neat from the nursery it came from and is now just doing it's own thing.

I give mine a good hair cut when it's flowered,

I think french lavender is a more clump forming variety.

Happy gardening.

If its growing in conditions which are too shady, lavender can sometimes do this regardless of variety, but I made the same mistake as you and bought the wrong one and it does exactly this, drives me bonkers, all the flower stems laying over everything else. Munstead is a much better option, and I'm currently growing Hidcote in hopes it doesn't do this.