I have a nice Otto Quasti lavender that looks great until it blooms. (Actually I have several in different areas and they all do this) Then the thing falls open in the middle and gets about 5' wide covering neighboring dianthus and verbena.

It gets full sun and performs beautifully -except for the falling open in the middle.

I cut it back harder than ever this year -to about 6" inches-I did this about 6 weeks ago too, after blooming.

What can I do to prevent this from happening next year without sacrificing blooms?

I was thinking of cutting it back again in August to keep it smaller but still have enough time to develop new growth.

I also removed all rooted areas around the mother plant.

Thanks!