New landscape shrub

Yesterday, while cruising a local nursery for late season bargains, the Phactors encounter a little shrubby plant with lavender flowers, and what was pretty interesting was the TPP had never heard of it.  Didn't even know what family it was in, even with flowers, and that's unusual.  Leptodermis oblonga.  Hmm, so who do you call?  Dirr!  But this plant is not in his Manual of Woody Landscape Plants, the Bible of woody ornamentals here in eastern North America.  Not in Dirr?  So what is this thing costing $14.99 minus the late season discount.  Dwarf lilac shrub?  Olive family?  Well, it has opposite leaves, but otherwise not a good fit.  The resemblance to lilac is superficial at best, the flowers are tubular and pinkish purple. Turns out this genus is in the Rubiaceae, the coffee family.  That explains a lot because while tropical species look rubiaceous, native species for us are smallish herbs that don't look like typical rubiads really.  Now the key thing is always cold hardiness and supposedly this species comes from Northern China and hardy in zone 5, unless they lied or unless this is an alpine plant, which while cold hardy will literally burn up in our Midwestern summer heat.  Probably not an alpine from Northern China, especially as an upright little shrub, so having passed the critical tests, and having a spot for a smallish shrub, we bought one.  Anyone out there with any experience with this species?  Anyone from Northern China?