Wow this taxon is a mess. A summary:

L. intermedia + L. frutescens = L. violacea (POWO)
L. intermedia + L. violacea = L. frutescens (ITIS; NatureServe)
L. frutescens valid, L. intermedia = L. violacea (VASCAN; BONAP)
L. intermedia valid, L. frutescens = L. violacea (GBIF)

This makes me seriously doubt keys like Michigan Flora which treat some combination of these three as separate species. There certainly appears to be a peduncled form and non-peduncled form of this species but whether these are different species, let alone what they should correctly be respectively called, is a mystery to me.

What say @bouteloua @loarie @charlie etc?

I think the citation of @bouteloua is in line with Haines (Flora Novae Anglian) and Voss/Reznicek (Michigan Flora). Just two species here - L. violacea and L. frutescens. The confusion is explained by Werier in the New York Flora Atlas, under both species. To whit:

This taxon has recently gone by the name L. intermedia. The nomenclatural history of Lespedeza frutescens, L. intermedia, and L. violacea has been complex. The type of Hedysarum violaceum L., which is the name Lespedeza violacea is based on, is a specimen of what has recently gone by the name L. intermedia. The specific epithet violaceum has priority and therefore L. violacea is the correct name for what has recently been called L. intermedia. Lespedeza intermedia becomes a superfluous name and is relegated to synonymy of L. violacea (Reveal and Barrie 1991). The name Lespedeza frutescens is the correct name for what has recently been called L. violacea. Lespedeza violacea is considered a misapplied name of L. frutescens and is also the correct name for what has recently been called L. intermedia (Reveal and Barrie 1991).