Species

• Common name: Carolina phlox / thickleaf phlox (also "summer phlox," "giant phlox")
• Scientific name: Phlox carolina L.
• Family: Polemoniaceae (phlox family)
• Confidence: High for Phlox carolina. Genus Phlox is certain. The species sits inside the genuinely difficult carolina / glaberrima / maculata complex, but after close examination every alternative in and around that complex is excluded by a concrete observed character (see the look-alike table and the confidence note below). The single load-bearing observation is the densely hairy (villous) calyx, verified under high-magnification crops.

Evidence (tied to the photos)

• Flower structure (IMG_4996, IMG_4999): 5 fused petals forming a salverform corolla — a long slender tube flaring to a flat face — with a small darker/paler eye and a hint of yellow at the throat. This is textbook Phlox.
• Petal lobes (IMG_4999 close-up): broad, rounded, and entire (not notched or cleft). This rules out the spring woodland phloxes (P. divaricata, P. stolonifera) and the often-notched P. pilosa.
• Leaves (IMG_4997): narrow, lanceolate, opposite, sessile, entire-margined, tapering to an acuminate tip, roughly ≤2 cm wide. The lateral veins are obscure (no strong looping submarginal "collecting vein"). Surface is matte and finely downy rather than glossy.
• Stem (IMG_4996 lower-stem crop, IMG_4997 node): green, unspotted, and finely pubescent (hairy). No purple speckling.
• Calyx / inflorescence (IMG_4998): calyx lobes are long, awl-shaped (subulate), and densely hairy; pedicels and inflorescence axis are conspicuously pubescent. Several spent brown flower heads are present — the plant has already been in bloom for a while.
• Color & habit: lilac-purple flowers in a rounded-to-shortly-cylindrical terminal cluster on an upright leafy stem — a tall (not creeping) phlox.

Look-alikes ruled out

Deciding features: obscure leaf venation on narrow leaves (excludes the paniculata group) → hairy, unspotted stem + rounded inflorescence (excludes maculata) → densely villous calyx (excludes the glabrous glaberrima, the nearest habitat match) → moist cove + mid-July bloom + tall habit + entire petals (excludes pilosa/amoena and the spring woodland phloxes). Everything that's left is P. carolina.

Habitat check

Good fit, with one honest nuance. Phlox carolina is "frequently found in the southern mountain regions" of NC — which includes Polk County and the Blue Ridge escarpment — in forests, woodland borders, and clearings on acidic soils. Weakley's Flora rates it FACU (facultative upland), so it's not a wetland obligate; but it readily occupies moist cove-forest ground, and a low valley ~50 m from a stream is comfortably within its range. (The wetter-loving P. glaberrima would actually be a slightly better moisture match, which is why the villous-calyx character — not habitat — is what settles the ID.)

Confidence note — what this rests on and what would change it

• Load-bearing observation: the densely villous calyx (and downy stem/leaves). This is what excludes the glabrous P. glaberrima, the only serious alternative left after venation and stem characters. The pubescence was checked on high-magnification crops and is unambiguous, so this is solid.
• Would raise it to near-certain: a look at the lower stem for faint purple speckling (final check against maculata), a ripe seed capsule (seed/valve characters), or a clear read of sepal width/midrib (broad+weak = carolina; narrow+strong = glaberrima).
• Residual caveat: the carolina/glaberrima/maculata complex intergrades and has been split/lumped repeatedly; a herbarium determination could assign it to a particular variety of P. carolina (e.g., var. carolina vs. var. angusta), but that doesn't change the species-level call.

Seed propagation

• Maturity window & the mid-July problem: Phlox carolina blooms May–July (can rebloom into fall). Seed capsules ripen roughly 4–6 weeks after each flower opens. In these photos the plant is in full flower (only a handful of spent heads), so mature seed is largely not yet available in mid-July — most of what was collected is flowers, not ripe capsules. Treat any seed collected now as immature / low viability and don't count on it.
• If/when capsules do ripen: phlox capsules dehisce explosively and fling the seed. To collect, tie a fine mesh/organza bag over browning capsules and gather seed as the capsules dry (typically Aug–Sep for the earliest flowers).
• Cleaning: let capsules finish drying in a paper bag; the seed pops free. Winnow out chaff.
• Stratification: sow fresh in fall outdoors, or give ~4–8 weeks cold-moist stratification (seed in damp medium, 34–40 °F / ~2–4 °C) before a spring sow.
• Germination: after stratification, warm (65–70 °F) with light; expect roughly 2–3 weeks to emerge, though phlox germination is often uneven.

Vegetative propagation — the realistic route this time

Because Colin physically collected leafy flowering stems (this is a plants/ cutting group, not ripe seed), softwood stem cuttings are by far the best bet, and mid-July is squarely inside the recommended May–July softwood window for this species.

• Softwood / basal stem cuttings (do this now):
  1. Recut each stem to 4–6 in, cutting just below a leaf node; remove the flower head and the lower pairs of leaves (root a non-flowering section if available).
  2. Dip the base in ~0.1% (1000 ppm) IBA rooting hormone (optional but speeds it).
  3. Stick in a fast-draining, humid medium — peat + coarse sand + perlite — kept moist, warm, bright but out of direct sun (a covered tray / humidity dome).
  4. Expect roots in ~2–4 weeks; pot on once well-rooted.
  • The collected stems have been handled and are wilting, so act fast and recut the bases (ideally under water) before sticking.
• Root cuttings: a classic phlox method, but taken from dormant roots in fall/winter — not applicable to what was collected.
• Division: reliable, but needs the whole crown — not an option from cut stems.

Grow-out in the NC Piedmont

• Hardiness: USDA zones ~5–9; the Piedmont is well within range.
• Light: full sun to part shade — light afternoon shade helps in hotter, drier Piedmont summers and keeps it closer to its cove-forest origins.
• Soil & moisture: rich, moist, well-drained, acidic soil. It came from a wet streamside cove and has low drought tolerance, so give it consistent moisture; amend heavy Piedmont clay with organic matter and avoid a baking, dry site.
• Bonus: Phlox carolina is notably more powdery-mildew resistant than garden phlox (P. paniculata) — the famous white cultivar 'Miss Lingard' is prized for exactly this — so it's a good, lower-maintenance choice for humid NC. Fragrant; attracts butterflies and hummingbirds. Give it decent air circulation anyway.

Actionable next step for Colin

Root the collected stems as softwood cuttings today. Recut each to ~5 in below a node (under water if possible), strip the flowers and lower leaves, dip in rooting hormone, and stick them in a moist peat/sand/perlite mix under a humidity dome in bright indirect light. Don't rely on seed from this mid-July collection — the capsules aren't ripe yet. If you can revisit the site in late Aug–Sep, bag a few browning seed heads to catch mature seed as a backup.

Sources

• NC State Extension — Phlox carolina (Carolina / Thick-leaf Phlox)
• NC State Extension — Phlox maculata (Meadow / Spotted Phlox)
• NC State Extension — Phlox glaberrima (Smooth / Marsh Phlox)
• NC State Extension — Phlox paniculata (Garden / Tall Phlox)
• Lady Bird Johnson Wildflower Center — Phlox carolina
• Flora of the Southeastern US (Weakley) — Phlox key
• Flora of the Southeastern US — Phlox carolina taxon detail
• Flora of the Southeastern US — Phlox glaberrima taxon detail
• NameThatPlant.net — Phlox carolina (Carolinas/SE)
• Native Plant Trust Go Botany — Phlox dichotomous key
• Clemson HGIC — Phlox
• RHS — Phlox carolina 'Miss Lingard'
• Plant Addicts — Propagating Phlox