Species

• Common name: Canada moonseed / common moonseed (a.k.a. "yellow parilla")
• Scientific name: Menispermum canadense L.
• Family: Menispermaceae (moonseed family)
• Confidence: High. Three independent lines converge: (1) range — Menispermum is documented in Polk County itself (5 research-grade iNaturalist records) and is common up the escarpment, while the two look-alikes are excluded or marginal here (below); (2) the bright-yellow long creeping woody rhizome is near-diagnostic for Menispermum ("yellow parilla"); (3) shallowly-lobed, entire, palmately-veined cordate leaves on a tendril-less twining vine. Ripe fruit (blue-black drupe + crescent seed) would be the final confirmation but wasn't collectable in mid-July; the ID does not depend on it.

⚠️ TOXIC — dangerous wild-grape mimic. All parts (fruit, seed, root/rhizome, foliage) are poisonous; the fruit has killed children. Principal toxin dauricine (plus berberine-type alkaloids) causes cardiac arrhythmia and seizures. Wash hands after handling the rhizome/cuttings; keep any fruit away from children and pets.

Evidence (tied to the photos)

The yellow woody creeping rhizome is the single strongest character and is near-diagnostic: moonseed's folk name "yellow parilla" refers directly to this yellow root, and it spreads by long creeping rhizomes. Neither look-alike shares it — Cocculus has a shallow suckering root with no rhizome and no yellow, and Calycocarpum has only a "woody base." (Note: leaf-underside hairiness is a weak separator — sources disagree on Cocculus pubescence — so I don't lean on it.)

Look-alikes ruled out

• Carolina coralbead / snailseed (Cocculus carolinus, now Nephroia carolina) — the only look-alike that genuinely shares this range, so the closest call. Deciding features (fruitless): Cocculus has a shallow suckering root with NO creeping rhizome and no yellow — the opposite of the bright-yellow creeping rhizome collected here; its petiole is not peltate; and its leaves are mostly unlobed (ovate/cordate/triangular) rather than shallowly angular-lobed. In fruit it's unmistakable: Cocculus = red drupe with a seed coiled into a near-complete snail circle; moonseed = blue-black drupe with an open crescent seed. Range clincher: iNat records center Cocculus in the SC upstate/Piedmont (Greenville 19, Pickens
  13. and it thins toward zero climbing into the higher NC mountain counties (Buncombe 0, Henderson 0); NC is its northern range edge. It reaches Polk Co. only sparsely (1 record). Confirming red-vs-black fruit in the fall would be a nice final check, but the rhizome alone already separates them.
• Cupseed (Calycocarpum lyonii) — the third native menispermaceous vine, and the one with deeply, sharply palmately 3–5 lobed, almost maple-like leaves. Ruled out on leaf form (our lobes are shallow and broad, not deeply cut), and decisively on range/elevation: Weakley's Flora does not accept it for NC at all (the SC report was rejected), it was absent from all eight escarpment counties checked on iNaturalist, and it is a low-bottomland plant capped around ~350 m — well below this ~640 m site.
• Wild grape (Vitis sp.) — the dangerous confusion. Ruled out: grape leaves are toothed/serrate, grapes have tendrils and shreddy bark, and grape seeds are round/pear-shaped. This plant has entire margins, no tendrils, and (in fruit) a crescent seed.
• Wild yam (Dioscorea villosa) — ruled out by venation: wild yam has arcuate, parallel-converging veins (monocot) and leaves that are never lobed; fruit is a 3-winged capsule. Our leaf is palmately netted and lobed.
• Wild potato vine (Ipomoea pandurata) — ruled out by the root: it makes one enormous single fleshy tuber (pounds), not a slender yellow creeping rhizome; leaves are entire/fiddle-shaped (never lobed); flowers are large white funnels.
• Passionflowers (Passiflora lutea / incarnata) — ruled out: Passiflora climbs by coiled axillary tendrils (absent here), P. incarnata has serrate margins, and neither has a yellow creeping rhizome.

Habitat check

Strongly consistent, and now confirmed at the county level. Weakley's Flora of the Southeastern US gives moonseed's habitat as "moist nutrient-rich forests, especially on floodplains or lower slopes," plus streambanks/thickets — exactly a low-lying, within-50 m-of-a-stream, moist cove bottom.

County range (iNaturalist observations; research-grade in parentheses):

Moonseed is directly documented in Polk County and grows well up into the mountains (Buncombe/Asheville, ~600 m+), so the ~640 m collection site is comfortably within — not at the edge of — its elevational range. The pattern also separates the look-alikes geographically: Cocculus peaks in the SC Piedmont and fades out climbing the escarpment, and Calycocarpum is absent everywhere here.

Seed propagation

• Maturity window: drupes ripen blue-black in fall (~Sept–Oct).
• Mid-July collection = immature/absent seed. Any fruit now would be green and low-viability. If you want seed, flag the plant and return in Sept–Oct for fully-black, bloom-covered drupes.
• Note it's dioecious — seed only forms on a female plant that grew near a male.
• Cleaning: mash/float off the pulp, rinse, extract the single crescent seed.
• Stratification: ~60 days cold-moist stratification breaks dormancy (Prairie Moon code C(60)). Easiest: sow fresh outdoors in fall and let winter stratify. Germination is reported as "usually good." Grow seedlings through their first winter before planting out.

Vegetative propagation — your best path (and what you collected)

You dug a rooted rhizome segment with attached vine (IMG_4985) — that is the ideal propagule. Moonseed propagates readily by rhizome/sucker division.

1. Pot it up now. Lay the rooted rhizome piece in a deep pot of moist, humus-rich mix, barely covered, keep shaded and consistently moist. Because it already carries roots, it should establish without rooting hormone or a mist bench.
2. Alternatively/also: hardwood cuttings in autumn in a cold frame, or semi-ripe stem cuttings in summer under humidity.
3. Best division timing going forward: early spring as growth resumes.

Grow-out in the NC Piedmont

• Hardiness: USDA 4a–8b; the Piedmont (7b–8a) is comfortably in range.
• Light: part shade to full shade — a woodland edge, shaded fence, or arbor.
• Soil/moisture: wants moist, rich, medium-to-wet soil. Give it more water than typical dry Piedmont clay uplands — site it low, near a downspout, or irrigate.
• Support: it twines (no tendrils/pads), so provide a trellis, arbor, or shrub to climb (to ~12–25 ft).
• Cautions:
  • Spreads aggressively by rhizome and can be hard to contain — plant in a bed you can edge, use a root barrier, or keep it cut back.
  • Toxic berries — keep away from children/pets; the crescent seed is your field safety check vs. wild grapes.

Actionable next step for Colin

Pot the rooted rhizome segment immediately in deep, moist, humus-rich mix; keep it shaded and damp while it establishes — this is a near-guaranteed success and far better than seed given the mid-July timing. Optionally, mark the wild plant's location and revisit in September–October: blue-black grape-like drupes with a single crescent seed would put the ID beyond any doubt (vs. Cocculus' red fruit and coiled seed) and give you viable seed to cold-stratify as a backup. Do not taste any fruit — moonseed is deadly.

Sources

• NC State Extension Gardener Plant Toolbox — Menispermum canadense
• Will Cook / Carolina Nature — Menispermum canadense
• Flora of the Southeastern US (Weakley) — Menispermum canadense
• Lady Bird Johnson Wildflower Center — Menispermum canadense
• Illinois Wildflowers — Moonseed
• Flora of North America — Menispermum canadense
• Prairie Moon Nursery — Moonseed (stratification C(60))
• Plants For A Future / temperate.theferns.info — Menispermum canadense (propagation)
• NC State Extension — Cocculus carolinus (Carolina snailseed look-alike)
• NC State Extension — Dioscorea villosa (wild yam look-alike)
• NC State Extension — Ipomoea pandurata (wild potato vine look-alike)
• Wikipedia — Menispermum canadense (toxicity / dauricine)
• iNaturalist — Menispermum canadense (county records, taxon 130900)
• iNaturalist — Nephroia carolina / Cocculus carolinus (county records, taxon 1555999)
• Flora of the Southeastern US (Weakley) — Nephroia carolina (Cocculus carolinus)
• Flora of the Southeastern US (Weakley) — Calycocarpum lyonii (NC report rejected)
• Flora of North America — Menispermaceae key (peltate leaf is diagnostic of Menispermum)
• Lady Bird Johnson Wildflower Center — Cocculus carolinus (shallow suckering root, no rhizome)
• Minnesota Wildflowers — Menispermum canadense (long creeping rhizome)
• A Modern Herbal (Grieve) — "Yellow Parilla," the yellow root
• Wikipedia — Calycocarpum (cupseed; low-elevation range, ≤~350 m)