Species

• Genus / family: Hydrangea — Hydrangeaceae. Confidence: Very high (diagnostic fruit + inflorescence, see Evidence).
• Segregate (which wild hydrangea): genuinely unresolved from one indoor photo, but the needle moved. After white-balancing the image (below), H. radiata (silverleaf) — the species the geography would predict — is argued against, and the specimen's own characters best fit H. cinerea (ashy hydrangea), with typical H. arborescens s.s. (smooth hydrangea) as the fallback. Confidence at species level: moderate, leaning cinerea ≈ radiata > arborescens. A 40× hand-lens settles it (see "Definitive test").
• Modern floras treat these as three species (Pilatowski 1980); older treatments lump them as H. arborescens subsp. radiata / subsp. discolor (= cinerea). Propagation is identical across all three, so the unresolved segregate does not change what Colin should do.

Only one photo in this folder (IMG_4986.jpg) — a hand-held cut stem with its infructescence.

Evidence (from IMG_4986.jpg)

• Fruit is the clincher. Each unit is a tiny green capsule with two persistent, divergent styles ("rabbit ears") and ~8–10 longitudinal ribs, topped by a persistent calyx rim. A 2-carpellate, ribbed, style-crowned capsule massed in a many-flowered cluster is textbook Hydrangea (clearest in the extreme close-ups).
• Inflorescence: a large, broad, much-branched corymb of hundreds of small units, and — importantly — all-fertile: no ring of enlarged 4-sepaled showy sterile "ray" florets is visible. This is a diagnostic character (see below), not just an aesthetic note.
• Leaves: simple, broadly ovate with a rounded-to-cordate base and acuminate tip, arrangement consistent with the opposite leaves of Hydrangea.
• Pubescence: flower stalks/pedicels and petioles are densely, finely hairy (velvety), and the leaf undersides are evenly, finely tomentose over the whole blade (a frosted matte texture, not hairs-on-veins-only).

Color analysis — why the first "silvery" impression was a lighting artifact

The photo was shot indoors under warm (tungsten) light on a wood floor, which pushed everything cream/warm and made the pale leaves look silvery. I white-balanced the image two ways (gray-world; 97th-percentile white-patch) and re-measured the leaf undersides:

• Even after neutralizing the warm cast, every pale leaf surface — including the back-folded and topmost leaves whose undersides face the camera — reads clearly GREEN, not white or neutral. Bright-lit underside patches measured ≈ RGB (130, 164, 127) — green-dominant, green-excess +30 to +36, low-but-nonzero saturation. A radiata underside (dense felt that entirely masks the green → bright white/silver) would resolve to near-neutral, high brightness after correction. It does not. → the undersides are genuinely green/gray-green, not white.

Which hydrangea? (revised)

Definitive key characters, verbatim from Weakley's Flora of the Southeastern US (leaf underside is the primary separator):

Mapping the photo onto the key:

• Underside color: pale green / gray-green, green NOT masked (color analysis above). → excludes radiata; fits cinerea or arborescens.
• Underside pubescence: evenly tomentose over the whole blade (frosted, not veins-only). → fits the tomentose pair cinerea/radiata; argues against glabrous-bladed arborescens.
• Intersection of those two = H. cinerea.
• Sterile florets: none visible (all-fertile corymb). → matches cinerea/arborescens (0–3); cuts against radiata (usually 2–15). A second, independent character pointing away from radiata.
• Densely gray-hairy inflorescence stems: the "best identifying feature" cited for cinerea.

So the specimen's morphology points to H. cinerea (ashy hydrangea), with H. arborescens s.s. the runner-up.

The honest tension: morphology vs. geography

The one thing pulling the other way is local abundance. Herbarium records (GBIF preserved specimens) for the Saluda escarpment show radiata is the dominant wild hydrangea here — ≈ 43 Polk County records (incl. Pearson's Falls Glen, Green River Cove, and "ca. 1 mi NE of Saluda") vs. only ≈ 4 for cinerea and ≈ 5 for arborescens. (This also corrects my first draft, which guessed radiata might not reach Polk County — it not only reaches it, it dominates, following the escarpment east from the Highlands–Cashiers core.) H. cinerea is documented at Saluda too (a specimen labeled "Saluda… damp woods"), just uncommonly.

Weighing a strong radiata base rate against morphology that fits cinerea:

• H. cinerea — best morphological fit (even tomentose gray-green underside, no showy sterile florets, hairy gray stems), but locally uncommon.
• H. radiata — best geographic/base-rate fit (the abundant escarpment taxon in a moist cove exactly like this), but its two defining characters (bright-white underside; showy sterile florets) are both absent in the photo. Not excluded outright — young/shaded leaves can be "grayish" and sterile florets are "rarely absent" — but the evidence is against it.
• H. arborescens s.s. — possible (green underside, no sterile florets), but the even whole-blade tomentum fits it less well than cinerea.

Net: roughly a cinerea ⇄ radiata toss-up (I lean cinerea on characters), arborescens trailing. Species-level confidence: moderate. This is a real improvement over the first draft's overconfident radiata lean, which rested on a lighting artifact.

Definitive test (resolves it in seconds, on the physical material)

Under a 40× loupe, look at a mature leaf underside:

• Green entirely hidden by white felt; hairs smooth (no chalky bumps) → radiata.
• Gray-green with green showing through; hairs conspicuously tuberculate (chalky bumps) → cinerea.
• Green blade, hairs only on the veins/midrib → arborescens.

Also check the fresh corymb for any large 4-sepaled showy sterile florets (present → radiata).

Look-alikes ruled out

• Elderberry (Sambucus canadensis) — same streamside habitat and clusters of little green spheres, but has pinnately compound leaves and smooth drupes, not simple cordate leaves and ribbed, 2-styled capsules. Ruled out by leaf and fruit.
• Cultivated 'Annabelle'-type smooth hydrangea — big sterile snowball heads; this is an all-fertile wild corymb, so not an escaped mophead.
• Panicled hydrangea (H. paniculata, non-native) — truly pyramidal panicle with conspicuous sterile florets; underside not white-felted. Doesn't match.
• Viburnums / dogwoods — wrong fruit (drupes), no 2-styled ribbed capsules.

Habitat check

Consistent, and consistent with all three candidates. Wild hydrangeas of this complex are classic moist-cove, streambank, rocky mesic-forest plants of the western-NC mountains — the "within 50 m of a stream, low valley" note fits perfectly. Elevationally Saluda (2000 ft ≈ 610 m) sits inside the range of both radiata (200–1200 m) and cinerea (100–700 m). A moist, cool, low escarpment cove is the textbook radiata niche; cinerea leans a bit drier / interior / mafic-calcareous, which is the one habitat nuance that (weakly) counters the morphology-based cinerea lean.

Seed propagation — mid-July verdict: too early, seed not viable

• Maturity window: flowers May–Jul; capsules ripen and dry to brown in fall (≈Sept–Oct), then split to shed dust-fine seed over fall/winter.
• Your mid-July material is immature — capsules are green and soft, styles still fresh — so there is essentially no ripe, viable seed inside yet. Don't count on germinating this.
• If you want seed: revisit the same plant in October, once heads are brown and dry, clip a few, dry them in a paper bag for a few days, then tap out the tiny seed.
• Sowing (ripe seed): surface-sow — scatter on moist mix, do not bury (they need light and are near-microscopic). No cold stratification required; sow fresh in fall or in spring. Keep humid and bright; germination is typically a few weeks under warm conditions.

Vegetative propagation — do this now (your best shot)

The H. arborescens complex roots extremely easily from cuttings — this is the payoff for a July collection, and it works the same regardless of segregate.

• Softwood/greenwood cuttings (ideal, right season): 4–6" tips with a couple of nodes, strip lower leaves, halve the remaining leaves to cut water loss, optional IBA (~2,500–5,000 ppm) but often unnecessary, stick in moist perlite/peat (or perlite/bark), keep under high humidity (dome/bag) in bright shade. Roots in a few weeks.
• Use the collected stem now — trim it into node cuttings before it wilts further; hydrangea softwood is forgiving.
• Layering (backup, if you revisit): pin a low branch to moist soil; it roots at the contact and can be severed next season.

Grow-out in the NC Piedmont

• Hardiness/fit: all three are comfortably hardy and adaptable in the Piedmont (≈ USDA 5–9); the change from the collection site is more heat, heavier clay, less summer moisture.
• Site: part shade / morning sun with afternoon shade; full Piedmont sun scorches unless kept moist.
• Soil & water: rich, humusy, consistently moist but well-drained; amend clay with compost and mulch. Expect it to flag in drought — water in dry spells.
• Note: if the loupe check comes back cinerea (ashy), that's the most heat/drought tolerant of the three — an even easier Piedmont plant. All bloom on new wood, so prune in late winter if at all.

Actionable next steps

1. Root cuttings from the collected stem immediately — 4–6" node cuttings, halve the leaves, moist perlite under a humidity dome in bright shade. This is the viable path from July material.
2. Ignore the green capsules for seed; if you want seed, return to the plant in October for brown, dry heads.
3. To settle the species: put a mature leaf underside under a 40× loupe and check hair tubercles + whether the felt masks the green; glance for any big showy sterile florets. That one look decides cinerea vs. radiata vs. arborescens.

Sources

• Weakley / Flora of the Southeastern US — genus Hydrangea key · radiata · cinerea · arborescens
• Flora of North America, Vol. 12 (C. Freeman) — genus (trichome tubercles) · radiata · cinerea
• GBIF — Hydrangea radiata occurrences (Polk Co. escarpment specimens)
• NC Extension Gardener Plant Toolbox — Hydrangea radiata · Hydrangea arborescens
• Arnold Arboretum / Arnoldia — "The Wild Hydrangeas of Mt. Cuba Center"
• Wikipedia — Hydrangea cinerea · Hydrangea radiata
• Will Cook, Carolina Nature — Wild Hydrangea · Lady Bird Johnson Wildflower Center — H. arborescens
• Gardener's Path — Collecting & planting hydrangea seed