Species

• Canada moonseed, common moonseed, also called yellow parilla
• Menispermum canadense L.
• Menispermaceae, the moonseed family
• Confidence high. Three independent lines converge. First, 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). Second, the bright-yellow long creeping woody rhizome is near-diagnostic for Menispermum. Third, shallowly-lobed, entire, palmately-veined cordate leaves on a tendril-less twining vine. Ripe fruit (blue-black drupe plus crescent seed) would be the final confirmation but wasn't collectable in mid-July, and the ID doesn't depend on it.

⚠️ Toxic, and a close mimic of wild grape. All parts (fruit, seed, rhizome and root, foliage) are poisonous, and the fruit has killed children. The principal toxin is dauricine, plus berberine-type alkaloids, causing cardiac arrhythmia and seizures. Wash hands after handling the rhizome or cuttings, and keep any fruit away from children and pets.

Evidence (tied to the photos)

The yellow woody creeping rhizome is the strongest character here and is near-diagnostic. Moonseed's folk name "yellow parilla" refers directly to this yellow root, and the plant 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." Leaf-underside hairiness is a weak separator since sources disagree on Cocculus pubescence, so I don't lean on it.

Look-alikes ruled out

• Carolina coralbead or snailseed (Cocculus carolinus, now Nephroia carolina), the only look-alike that genuinely shares this range, so the closest call. Without fruit, the deciding characters: 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, or triangular) rather than shallowly angular-lobed. In fruit it's unmistakable: Cocculus has a red drupe with a seed coiled into a near-complete snail circle, moonseed a blue-black drupe with an open crescent seed. Range backs this up. iNat records center Cocculus in the SC upstate and Piedmont (Greenville 19, Pickens 13) and it thins toward zero climbing into the higher NC mountain counties (Buncombe 0, Henderson 0), NC being its northern range edge. It reaches Polk Co. only sparsely, 1 record. Confirming red versus 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, since our lobes are shallow and broad rather than deeply cut, and decisively on range and elevation: Weakley's Flora doesn't accept it for NC at all (the SC report was rejected), it was absent from all eight escarpment counties I 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. Grape leaves are toothed or serrate, grapes have tendrils and shreddy bark, and grape seeds are round to pear-shaped. This plant has entire margins, no tendrils, and in fruit a crescent seed.
• Wild yam (Dioscorea villosa): ruled out on venation. Wild yam has arcuate, parallel-converging monocot veins and leaves that are never lobed, and its fruit is a 3-winged capsule. This leaf is palmately netted and lobed.
• Wild potato vine (Ipomoea pandurata): ruled out on the root. It makes one enormous fleshy tuber weighing pounds, not a slender yellow creeping rhizome. Leaves are entire or fiddle-shaped, never lobed, and the flowers are large white funnels.
• Passionflowers (Passiflora lutea, P. incarnata): 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 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 and thickets. That is this site: a low-lying moist cove bottom within 50 m of a stream.

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

Moonseed is directly documented in Polk County and grows well up into the mountains (Buncombe and Asheville, ~600 m+), so the ~640 m collection site sits comfortably within its elevational range rather than at the edge. The pattern separates the look-alikes geographically too: 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.
• The mid-July collection means immature or absent seed. Any fruit now would be green and low-viability. For seed, flag the plant and go back in Sept–Oct for fully black, bloom-covered drupes.
• It's dioecious, so seed only forms on a female plant that grew near a male.
• Cleaning: mash and float off the pulp, rinse, extract the single crescent seed.
• Stratification: ~60 days cold-moist stratification breaks dormancy (Prairie Moon code C(60)). Easiest is to sow fresh outdoors in fall and let winter do it. Germination is reported as "usually good." Grow seedlings through their first winter before planting out.

Vegetative propagation — the best path, and what I collected

I dug a rooted rhizome segment with attached vine (IMG_4985), which is the ideal propagule. Moonseed propagates readily by rhizome and sucker division.

1. Pot it up now. Lay the rooted rhizome piece in a deep pot of moist, humus-rich mix, barely covered, and keep it shaded and consistently moist. Because it already carries roots, it should establish without rooting hormone or a mist bench.
2. Also possible: hardwood cuttings in autumn in a cold frame, or semi-ripe stem cuttings in summer under humidity.
3. Best division timing going forward is 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 and 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 rather than gripping with tendrils or pads, so provide a trellis, arbor, or shrub to climb, to ~12–25 ft.
• Cautions:
  • It spreads aggressively by rhizome and can be hard to contain. Plant in a bed I can edge, use a root barrier, or keep it cut back.
  • The berries are toxic. Keep them away from children and pets. The crescent seed is the field safety check against wild grapes.

Next step

Pot the rooted rhizome segment immediately in deep, moist, humus-rich mix, and keep it shaded and damp while it establishes. Near-guaranteed, and far better than seed given the mid-July timing. Optionally mark the wild plant's location and revisit in September or October: blue-black grape-like drupes with a single crescent seed would put the ID beyond doubt, against Cocculus' red fruit and coiled seed, and give me 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)