Don’t Plant Italian Arum (Arum italicum): Invasive in 11 States, Toxic Like Peace Lily, and Nearly Impossible to Remove

If you already steer a curious dog or a toddler away from the peace lily on the windowsill, you already understand the exact danger a much prettier-looking garden plant poses outdoors. Italian arum (Arum italicum) is sold at nurseries every fall as a “problem-solver” groundcover — something that actually does something in a shaded bed once everything else has gone dormant. It’s also documented as naturalized or invasive in at least 11 US states, and it defends itself with the identical chemical weapon as the peace lily you already keep out of reach indoors.

Here’s how to identify it, why botanists keep adding new states to its range, how to avoid ripping out a native look-alike by mistake, and what to plant instead if you want the same shaded-bed coverage without the liability.

What Italian Arum Actually Is (and Why Garden Centers Sell It)

If you’ve spotted glossy, arrow-shaped leaves marbled with cream-white veining pushing up in a shaded bed in October or November — right when nearly everything else in the garden has gone dormant — you’re almost certainly looking at Italian arum. It’s a tuberous perennial native to southern and western Europe, hardy in USDA zones 5-9, growing 12 to 18 inches tall and wide in part shade to full shade with consistently moist, humus-rich soil.

The leaf pattern reverses the calendar most gardeners expect. In milder climates, new leaves emerge in autumn and stay green through winter; in colder regions the foliage dies back and re-emerges in early spring instead. Either way, by summer the leaves are gone completely — and that’s precisely when a creamy-white, hood-shaped spathe gives way to a dense, club-like spike of berries that ripen from green to bright orange-red by August.

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That reverse dormancy is exactly what makes Italian arum an easy sell and a quiet invader at the same time. Garden centers market it as filling the “nothing else is doing anything” gap in a winter shade bed — but that same gap is when most gardeners have stopped actively weeding, and the plant disappears completely just as spring and summer weeding season ramps up. A colony can add ground each year almost entirely unnoticed, between the two seasons when people are actually paying attention to that bed.

The Toxicity Mechanism — Same Weapon as Your Peace Lily

Peace lily (Spathiphyllum) and Italian arum aren’t the same genus, but they belong to the same plant family, Araceae — and calcium oxalate raphides are that family’s signature defense mechanism. That’s why two plants that look nothing alike cause nearly identical symptoms if chewed. We’ve broken down the full mechanism and symptom picture for the houseplant version in our guide to peace lily toxicity in cats and dogs — the chemistry described there is the same chemistry at work outdoors in Italian arum.

Every part of the plant — leaves, stems, corms, and berries — stores its toxin as bundles of needle-shaped calcium oxalate crystals, packed inside specialized plant cells. Biting or crushing the tissue ruptures those cells, and the swelling gel inside forces the needle bundles outward into whatever caused the damage: a mouth, a tongue, a paw pad. North Carolina State University Extension classifies Italian arum as a “high severity poison,” with ingestion capable of causing throat and tongue swelling severe enough to interfere with breathing, and in the worst documented cases, death. The Royal Horticultural Society lists it as toxic if eaten and a skin and eye irritant on contact alone, which is why handling the plant for removal calls for gloves.

The berries carry the highest concentration of raphides of any part of the plant, and they’re also the part most likely to tempt a curious dog or toddler, since bright orange-red clusters at ground level read as an obvious, edible-looking target. Treat them the same way you’d treat any other unknown berry patch: assume every part is off-limits, and call ASPCA Animal Poison Control at (888) 426-4435 immediately if a pet mouths any part of the plant.

Documented Invasive or Regulated in At Least 11 States

This isn’t a niche West Coast problem anymore. Pulling together official state noxious-weed listings, invasive plant council assessments, and peer-reviewed floristic records turns up documented naturalized or regulated populations of Italian arum in at least 11 states, and the list keeps growing.

That 11-state count is also almost certainly an undercount, and not a static one. Botanists published Italian arum’s first official flora record for Oklahoma after finding a naturalized population near Spiro, in Le Flore County, in 2025 — a reminder that this plant’s documented range gets a new entry almost every year as regional botanists and invasive-species partnerships catch up with where it’s actually spreading, not just where it was first noticed decades ago.

Nearly every documented population traces back to the same starting point: a deliberately planted garden specimen. Nobody is finding Italian arum growing wild a hundred miles from the nearest neighborhood. What changes the story from “one contained garden bed” to “naturalized population” is what happens after planting — lateral tubers push the original clump outward underground, and birds eat the ripe berries and carry the seed into nearby woods, hedgerows, and neighboring yards. That’s also why a single homeowner deciding to remove it doesn’t fully solve the problem if the plant is already fruiting nearby; it’s a bed-by-bed and neighborhood-by-neighborhood effort, not a one-time fix.

Don’t Confuse It With Jack-in-the-Pulpit

The biggest identification mistake with Italian arum doesn’t cost you the invasive plant — it costs you a native one. Jack-in-the-Pulpit (Arisaema triphyllum) grows in similar shaded, moist woodland conditions across central and eastern Canada and the US, and from a few feet away, an unbloomed patch of either plant can look like a green blur. Up close, they’re easy to tell apart.

I’ve seen more than one gardener rip out a slow-growing Jack-in-the-Pulpit while chasing down Italian arum in the same shady corner — the leaf shape is the fastest tell, so check that before you dig anything up. And note that misidentifying them doesn’t change your handling precautions either way: Jack-in-the-Pulpit is also toxic via its own calcium oxalate crystals, so both plants call for gloves and the same “keep pets and kids away from it” rule. The only thing that changes is whether you’re removing an invasive species or destroying a native one for nothing.

Why It’s a Problem in America but Not (Officially) in Britain

The Royal Horticultural Society lists Italian arum as native to Great Britain and Ireland, hardy to RHS rating H6 — meaning it survives winters across the entire UK and northern Europe without protection. Even there, though, the RHS flags it as a plant that “has the potential to become a nuisance if not managed well,” in its guidance on garden thugs.

That contrast is a textbook case of what invasion ecologists call enemy release: in its native and long-naturalized European range, Italian arum’s spread is held in check by competing native flora, co-evolved herbivores, and pathogens that have kept pace with it over a very long time. Transplant the same corm into an American garden and none of those checks exist. There’s no native competitor pushing back, no local insect or fungal pathogen specialized enough to slow it down — so the plant’s biology stays exactly as aggressive as it always was, but the brakes are gone. That’s the general pattern behind most garden-escapee invasions, and it’s a big part of why “it’s fine in England” and “it’s a documented invasive in 11 US states” can both be true statements about the exact same species.

If You Already Have It: Removal That Actually Works

Skip the once-and-done herbicide spray — it won’t work, and here’s the process that actually does. Oregon State University Extension is blunt about it: even correctly applied glyphosate or imazapyr may not achieve complete control, because any tuber fragment left behind in the soil can resprout. California Invasive Plant Council goes further, describing established colonies as “very difficult to control” by design, since the plant reproduces through both underground lateral tubers and long-distance, bird-carried seed at the same time.

The realistic plan runs over multiple seasons, not one weekend:

• Stop new seed first. As soon as you see the first hint of orange on the berry spike, cut it and seal it in a trash bag — never the compost bin, since home compost heat doesn’t reliably kill the seed. This is the single highest-leverage step, because seed dispersal is how the colony jumps beyond its current footprint.
• Dig, then sift. Remove the entire plant including tubers, roots, and stems, then sift through the disturbed soil by hand for any fragments. A piece the size of a fingernail can start a new plant.
• Expect regrowth and plan for it. Persistence over several years is the norm, not a sign you did something wrong the first time.
• If chemical control is necessary, treat it as one part of a multi-year plan rather than a single fix, and follow label directions exactly — Extension guidance doesn’t promise complete control even then.
• Clean your tools and boots before moving on. Oregon State University Extension specifically flags footwear and equipment as a seed-transport route between infested and clean areas of a property — a habit worth keeping even after the visible plant is gone.

One caveat worth stating plainly: if Italian arum has already fully naturalized across a wooded acre rather than a single garden bed, trying to eradicate every corm in one season isn’t realistic, and spraying broadly can do more collateral damage to the surrounding native plants than the arum itself. In that situation, prioritize cutting berries before they ripen every single year to stop the colony’s spread, and work the existing patch back gradually rather than attempting a one-shot eradication.

What to Plant Instead

If the appeal was ground cover for a shaded bed that still looks like it’s doing something in the off-season, you don’t have to give that up — you just need a plant that isn’t actively expanding its range across 11 states while it does it. Our guide to replacing invasive ornamentals with native keystone plants covers 15 direct swaps built around the same goals — year-round structure, low maintenance, shade tolerance — without the invasive spread or the toxicity liability, and with the added benefit of actually supporting local pollinators and wildlife instead of displacing them.

Key Takeaways

Italian arum earns its spot in garden centers honestly — it really does fill a gap nothing else covers in a winter shade bed. But “documented invasive or regulated in at least 11 states and counting,” plus a toxicity mechanism identical to a houseplant most households already handle carefully, is a real cost, not a hypothetical one. If you’re planting new this fall, choose a native alternative instead. If you already have it, the highest-leverage move is also the simplest: get to the berries before they turn orange, every single year, until the colony stops expanding.

Frequently Asked Questions

Is Italian arum illegal to plant?
Only in Washington State, where it’s a regulated Class C noxious weed banned from sale, transport, and distribution. It isn’t federally regulated, and most states where it’s flagged as invasive — including California and Oregon — still allow it to be sold at nurseries.

Can I compost the berries?
No. Oregon State University Extension specifically warns against composting Italian arum berries, since a typical home compost pile doesn’t reliably reach the heat needed to kill the seed. Seal them in a trash bag instead.

Will one plant really take over my garden?
Given enough time, yes. California Invasive Plant Council notes it spreads through two separate mechanisms at once: lateral tubers that expand a single plant’s footprint underground, and bird-dispersed seed from the berries that can establish new colonies well outside the original bed.

Is Arum italicum ‘Marmoratum’ a different, safer plant?
No. ‘Marmoratum’ is simply the most commonly sold ornamental cultivar name, selected for extra-bright leaf marbling — not a distinct species. The toxicity and invasive behavior documented throughout this article apply to that cultivar too.

Can it spread to my yard even if I never planted it?
Yes. Birds eat the ripe berries and disperse the seed well beyond the original planting, which is how Italian arum ends up naturalized in woods, hedgerows, and neighboring properties that never had it deliberately planted. If a neighbor’s bed has established berry spikes, monitoring your own shaded areas each fall is a reasonable precaution.

Sources

1. NC State Extension. Arum italicum (Cuckoo Pint, Italian Arum). NC State Extension Gardener Plant Toolbox
2. Washington State Noxious Weed Control Board. Italian Arum
3. Oregon State University Extension Service. How can I control or eliminate Italian arum in my yard?
4. California Invasive Plant Council. Arum italicum Plant Profile
5. Missouri Botanical Garden. Arum italicum. Plant Finder
6. Royal Horticultural Society. Arum italicum
7. Journal of the Botanical Research Institute of Texas. First record of Arum italicum (Araceae) from the Oklahoma (U.S.A.) flora
8. Lower Hudson Partnership for Regional Invasive Species Management. Italian arum (Arum italicum)
9. NC State Extension. Arisaema triphyllum (Jack-in-the-Pulpit). NC State Extension Gardener Plant Toolbox