Moonseed

The vine that ripens fake grapes. It twines through the same hedgerows, fruits blue-black in the same weeks, and its berries have killed children - and one crushed berry tells you which vine you are holding.

How to recognize it: one crescent seed instead of several pear-shaped ones, no tendrils anywhere on the vine, smooth-edged leaves on a stalk set in from the rim, and slender bark that never shreds.

You never plant moonseed. What follows is the identification, in the order of how much weight each check can carry.

1. The seed — decisive. Cut or crush one berry. Moonseed: a single seed, flattened like a small coin, ridged around the rim, and curved into a distinct crescent moon. Grape: two to four seeds, plump, hard and pear-shaped with a little beak. This test needs one fruit and five seconds, it works regardless of season, ripeness or region, and it is the only check worth staking a jelly pan on.

2. Tendrils — almost as good. A grapevine climbs by forked tendrils thrown opposite the leaves; they are present on new growth and persist as dried curls on old wood. Moonseed has no tendrils at all and climbs by twining its whole stem round its support. Scan a length of vine: no tendrils, no grapes.

3. The leaves. Grape leaves are toothed right round the margin, and the stalk meets the blade at a notch on the leaf edge. Moonseed leaves are broadly heart-shaped or shallowly 3- to 7-lobed with a smooth, untoothed margin, and the stalk joins the underside of the blade a little in from the rim, so the leaf sits on the stalk like a shield.

4. The bark, in winter. Old grapevines carry thick, shaggy bark that peels in long strips. Moonseed stays slim, with tight bark that does not shred.

Two other hedgerow vines get caught up in the same question. Virginia creeper also hangs dark-blue berries in autumn — it is separated instantly by its palmate leaves of five leaflets, and its fruit is not edible either. And Canada moonseed's southern cousin, Carolina snailseed (Cocculus carolinus), does the same trick with red berries and a coiled snail-shaped seed. The rule that covers all of them: look inside the fruit before you eat anything from a hedge.

There is no care - only separation. Where it twines through a grape arbor, a hedge you pick from, or a fence a child can reach, cut it out at the base before the fruit ripens.

Moonseed is a native vine with genuine wildlife value, and in a woodland edge where nobody picks fruit it does no harm and needs no attention. The management question is only ever about where it is.

The situation that matters is moonseed growing up through a fruiting grapevine or a hedge you forage. That is not a freak occurrence — birds eat the berries and drop the seed along exactly the fence lines and woodland edges where wild grapes grow, so the two vines end up interwoven, with their fruit clusters hanging side by side at picking height. No amount of care in picking beats simply not having it there.

To remove it: cut the stem at ground level in late winter or early summer, well before the fruit colours, and pull the top growth out of the host plant. It resprouts from a spreading rootstock, so expect to cut it again for a season or two, or dig the crown out where you can reach it. Wear gloves. Bag the fruiting stems for the trash rather than composting them or leaving them where children and dogs can pick up windfalls.

If you keep a grape arbor, walk it once each summer specifically looking for a tendril-less stem among the grape wood. That one habit removes the whole hazard from your garden.

What to do if someone ate the berries, how to check a batch of picked wild grapes, and why one crescent seed means the whole batch goes in the bin.

Someone has eaten berries from a hedgerow vine and you are not certain what it was. Call poison control or emergency services immediately — do not wait for symptoms. Take a piece of the vine and a few of the fruit with you, ideally with one berry cut open so the seed is visible; the seed is what identifies it fastest for a clinician. Do not induce vomiting. Effects reported after moonseed ingestion include nausea and vomiting, weakness, and in significant doses convulsions; children are at risk from a much smaller quantity than an adult.

“I have already picked a bucket of wild grapes.” Before anything goes on the stove, cut open several berries from each cluster you picked and look at the seeds. Two to four pear-shaped seeds is a grape. One flat crescent is moonseed. If a single crescent seed turns up, throw the entire batch out — you cannot sort a mixed bucket afterwards, and a jelly pan gives no second chance to check.

“There is a vine in my arbor and I cannot tell which it is.” Look for tendrils. Grapes have forked tendrils opposite the leaves, on new growth and as dried curls on old wood. Moonseed has none and twines its stem instead. Then check a leaf: toothed margin and a stalk at the leaf notch is grape; smooth margin and a stalk set in from the rim is moonseed.

“Are the berries dangerous to touch or to pull out?” Handling the vine is not the hazard — ingestion is. Wear gloves anyway, wash afterwards, and keep cut fruiting stems out of reach of children and pets while you clear up.

“My dog ate some.” Call a veterinarian or an animal poison line. Do not wait to see whether it settles.

Named for its crescent seed, sold in the 1800s as yellow parilla and used to adulterate sarsaparilla - and a member of a plant family that also gave the world curare.

The name is literal. Menispermum is Greek for moon seed, and the family name Menispermaceae carries it too — the entire group is named for the crescent that this plant hides inside every berry. It is a rare case of a botanical name being the field mark.

The root had a nineteenth-century commercial life as yellow parilla, a bitter tonic in the eclectic materia medica, and it was traded as a cheap substitute for and adulterant of imported sarsaparilla — which is where the odd folk name Texas sarsaparilla comes from. It has no place in modern practice, and there is no safe home preparation of any part of this plant; the historical use is worth knowing only because it explains the names you may meet in an old herbal.

Its relatives put the alkaloid chemistry in perspective. The Menispermaceae include Chondrodendron, the South American vine that yielded curare, and Anamirta cocculus, whose picrotoxin-laden fruit was used to stun fish. This is a family that specialises in potent, fast-acting compounds, and North America's one common representative keeps up the tradition — wrapped in a package that looks exactly like a grape.

An eastern and central native, roughly zones 4-8, along rivers, woodland edges and fencerows - which is precisely the habitat wild grapes occupy, in every state where people forage them.

Moonseed is native across the eastern and central United States, roughly zones 4 to 8, from New England and the Great Lakes south to the Gulf and west to the eastern Plains. It favours moist, rich ground in part shade: riverbanks and floodplain woods, thickets, woodland edges, fencerows and roadside hedges, usually scrambling 10 to 20 feet through shrubs and small trees.

That description is also, almost word for word, the habitat of North America's wild grapes. The two share their range, their soil, their light, their supports and their fruiting season, and in much of the East they share the same hedge. This is not a plant you meet only in remote woods — it turns up in suburban fence lines and along the edges of gardens.

So wherever you live in that range, the practical conclusion is the same. If you forage wild grapes, or keep an arbor, learn the crescent seed and the missing tendrils, and check every year. It takes one berry and a few seconds, and it is the difference between a hedgerow jelly and an emergency call.