Species

• Genus and family: Hydrangea, Hydrangeaceae. Confidence very high, on the fruit and inflorescence (see Evidence).
• Which wild hydrangea: genuinely unresolved from one indoor photo, but the needle moved. After white-balancing the image (below), the evidence argues against H. radiata (silverleaf), which is the species the geography would predict, and the specimen's own characters best fit H. cinerea (ashy hydrangea), with typical H. arborescens s.s. (smooth hydrangea) as the fallback. Species-level confidence is 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 and subsp. discolor (= cinerea). Propagation is identical across all three, so the unresolved segregate doesn't change what I do next.

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

Evidence (from IMG_4986.jpg)

• Fruit settles the genus. 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 all fertile. No ring of enlarged 4-sepaled showy sterile "ray" florets is visible. That is a diagnostic character, 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 and finely hairy, almost velvety. The leaf undersides are evenly, finely tomentose over the whole blade, a frosted matte texture rather than hairs on the 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 reads clearly green rather than white or neutral, including the back-folded and topmost leaves whose undersides face the camera. Bright-lit underside patches measured ≈ RGB (130, 164, 127): green-dominant, green-excess +30 to +36, low but nonzero saturation. A radiata underside, where dense felt entirely masks the green and reads bright white or silver, would resolve to near-neutral and high brightness after correction. It does not. So the undersides are genuinely green to gray-green.

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 to gray-green, green not masked (color analysis above). Excludes radiata, fits cinerea or arborescens.
• Underside pubescence: evenly tomentose over the whole blade, frosted rather than veins-only. Fits the tomentose pair cinerea and radiata, argues against glabrous-bladed arborescens.
• Intersection of those two is H. cinerea.
• Sterile florets: none visible, an all-fertile corymb. Matches cinerea and arborescens (0–3) and cuts against radiata (usually 2–15). A second, independent character pointing away from radiata.
• Densely gray-hairy inflorescence stems, cited as the best identifying feature 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, including Pearson's Falls Glen, Green River Cove, and "ca. 1 mi NE of Saluda," against 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, on a specimen labeled "Saluda… damp woods," just uncommonly.

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

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

Net: roughly a cinerea to radiata toss-up, and I lean cinerea on characters, with arborescens trailing. Species-level confidence moderate. That's 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 with no chalky bumps: radiata.
• Gray-green with green showing through, hairs conspicuously tuberculate (chalky bumps): cinerea.
• Green blade, hairs only on the veins and midrib: arborescens.

Also check the fresh corymb for any large 4-sepaled showy sterile florets. If present, radiata.

Look-alikes ruled out

• Elderberry (Sambucus canadensis): same streamside habitat and clusters of little green spheres, but pinnately compound leaves and smooth drupes rather than 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): a truly pyramidal panicle with conspicuous sterile florets, and the underside isn't white-felted.
• Viburnums and 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, and the "within 50 m of a stream, low valley" note fits. 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, more interior, more 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 and winter.
• The 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 it.
• For seed, go back to the same plant in October once the 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, scattering on moist mix. Do not bury it. The seed is near-microscopic and needs light. 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

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

• Softwood or greenwood cuttings, ideal for the season: 4–6" tips with a couple of nodes, strip the lower leaves, halve the remaining leaves to cut water loss, optional IBA (~2,500–5,000 ppm) though often unnecessary, stick in moist perlite/peat or perlite/bark, keep under high humidity (dome or 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, as a backup on a return visit: pin a low branch to moist soil, it roots at the contact, and it can be severed next season.

Grow-out in the NC Piedmont

• Hardiness and 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, or morning sun with afternoon shade. Full Piedmont sun scorches unless it's kept moist.
• Soil and water: rich, humusy, consistently moist but well-drained. Amend clay with compost and mulch. Expect it to flag in drought, so water in dry spells.
• If the loupe check comes back cinerea (ashy), that's the most heat and 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. For seed, go back 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 the hair tubercles and whether the felt masks the green, then 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