I second Judy's idea. Use something more substantial than what looks to be leftover brick. One of the biggest mistakes I see (and I'm no expert by any stretch) is people not adequately sectioning off a "garden" from the rest of the yard. I can't tell from the picture but is there another edging of some sort starting in the lower left corner? If you have an area that large, you need something larger to not be dwarfed by the size of the space. Again, looking at the picture Judy posted, those are significantly larger bushes (and more of them) with the smaller plants like your daisies mixed in among them. It doesn't look like you would need to get rid of what you have, maybe just move them around to make larger holes for a more significant plant. I'm partial to ornamental grasses myself.