This probably won't be helpful, but I have catmint (Nepeta faassenii Select Blue bought from High Country Gardens back in 2015) and lavender (don't recall the variety, but I think an English lavender) in my Austin-area garden (clayey soil, so not great drainage) and for me, the catmint stays short, sprawls a lot, and the blooms are rather inconspicuous. My English lavender has bloomed and is lovely, but had some sporadic die-off during the winter (perhaps due to the lack of drainage). The shape of the two plants, for me, is very different - catmint spreads outward a lot but I can't get it to lift up off the ground. The lavender is a rounded shrub and is much taller, especially when blooming. I have googled the catmint variety and mine does not look at all like the photos so it seems likely that I am doing something wrong. Oh - also, if you have cats in the area, you'll need to protect the catmint until it grows large enough to fend for itself. Actually, that could be the problem for my plant - I know it gets frequent visits from the neighborhood strays. Based on their performance in my garden, I prefer the lavender. I also am not a huge fan of the catmint scent.

Perhaps a purple salvia could be a contender as well? I have a few blue salvias which bloom all summer and fall for me, but do die back during the winter.

Yes, looking at a blue salvia for our salvia bed. I think I will try the lavender!! We will amend the soil and being a raised bed, it may work! Thanks for your input.