rock cress - Aubrieta cultorum

None of the aubrietas will bloom for much longer than the phlox - all are considered to be mid to late spring bloomers.

FWIW, most perennial groundcovers will have a relatively limited bloom season - that is just the nature of perennials. They bloom for a couple weeks to a couple of months and then are done for the season. Annuals - with that biological urge to reproduce within the growing season - are generally the only plants with a season-long flowering period.

If you want a growing-season-long bloom period, you may have to consider a sequential assortment of flowering groundcovers. If you provide your location and sun conditions, perhaps we can get more specific.

And while it is not exactly considered a groundcover, the hardy geranium 'Rozanne' grows virtually throughout the US and in both sun and light shade and is recognized as having a very long bloom season. But it is more of a sprawling perennial than a true groundcover.

Here is a link that might be useful: Geranium Rozanne

Green & Gold (Chrysogonum virginianum) is one of the few long-blooming groundcovers though it hardly resembles phlox (yellow flowers) and it doesn't form a carpet of flowers like phlox. Blue Star Creeper (Isotoma fluviatilis) also produces (rather small) flowers for an extended period. Lithodora has a decent bloom period too -- spring into early summer. Plumbago resembles phlox but blooms late in the season so it makes a nice complement to creeping phlox.

Verbena Sissinghurst is the ticket! I planted this in my former Zone 6 garden and it was a reliable perennial and bloomer year after year. Drought tolerant too. You've got to like bright pink, however, because this variety comes only in pink.

There are numerous other varieties of ground cover verbena that come in other colors (in the blue, pink, red, white part of the rainbow) but in my experience, Sissinghurst is at the top of the list. No mildew, mites, etc. which I've encountered with other varieties.

June

Here is a link that might be useful: Verbena Sissinghurst

Thank you so much Juneroses, that advice was invaluable, and I LOVE pink verbena!

Lamium maculatum blooms all season and doesn't mind dry shade.

Check out potentilla x tonguei. Pretty orange flowers last a long time. Grows fast once established, maybe too fast for some applications. May be a little hard to find.