Around July 4th some of my perennials which have been spectacular for the past two months are now going to seed and although they’re still green, don’t add anything to the garden. This is true for veronica, salvia, and maltese cross in particular.
What I do around this date is to save any seed I want and then cut the plants down to the ground. I also usually add a bit of fertilizer to spur some new growth. Last year I got three distinct blooms using this plan and my gardens looked great. This year I’ll probably only get two blooms, but that is still one more than most people.
The other advantage I’ve found is that for veronica, buckeyes like to lay their eggs on this new growth.
I have experimented with this technique on other plants and have not duplicated the success.
If you know of any other butterfly perennials that this works with, let me know.