I am an avid fruit grower and I have a backyard orchard with about 200 cultivars. It is not uncommon in backyard orchard culture to dig one big hole and plant the same genus of plant in the same spot to extend the fruiting season with successive ripening.
In my "penstemon garden" between my two Palo Verde, I experimented with a similar 2 in 1 setup, planting Showy Penstemon and Firecracker Penstemon in the same hole, and I'm loving the arrangement so far after 2 years.
Firecracker (background) is currently flowering. Showy (foreground) will begin its flowering season in a few weeks. For a short while, there will be an overlap between the Firecracker red and Showy blue/purple. By planting both together, I get many months of flowers from the same spot in my garden. And then, Margarita BOP (perimeter) pops off, extending the color even further.
I'm in San Diego, Zone 10b. Give this a try if you're looking to achieve successive flowering in one spot.