History & Introduction

Macleaya cordata, commonly referred to as plume poppy, is a native species to Japan, eastern China, and parts of Taiwan. In China, the plant is used as a traditional medicinal herb known for its anti-inflammatory and antibacterial properties. 

The genus Macleaya is named for Alexander Macleay (1767-1848), a Scottish entomologist and Colonial Secretary for New South Wales and once the Secretary of the Linnean Society of London. The specific epithet refers to the cordate (heart-shaped) leaves.

The plume poppy is a flowering plant in the poppy family, Papaveraceae. It has large, dull green clusters of leaves with deep lobes, and cordate bases, and plumes of white flowers that bloom in July and August. Plume poppy is a rigorous, rhizomatous perennial that is cultivated as an ornamental plant, readily persisting and competing in cultivated settings, deciduous woods, thickets, old fields, ditches, roadsides, pond margins, and along waterways. The plume poppy is a hardy plant that can survive in Zone 4 winters. It grows best in full sun or partial shade, though it appears to thrive more readily and aggressively in shaded areas. 

It is seemingly unknown when the plume poppy was first introduced into the United States, however, today it occupies much of the eastern US, ranging in its distribution as far north as Maine, as far south as Alabama, and as far west as Illinois. This includes New York, where it is listed as a Tier 2 invasive species (early detection and eradication) in the state, and in LIISMA. 

Identification & Biology 

As mentioned, the plume poppy is cultivated as an ornamental plant that has begun to escape cultivation into various natural settings, including wooded areas, old fields, ditches, and along waterways. Plume poppy is an upright, 5-8’ tall rhizomatous perennial that boasts attractive plumes or panicles of branched, showy, radially symmetrical white flowers atop clusters of large, dull green, deeply lobed or scalloped leaves, sometimes possessing toothed margins. 

The coarse leaves are light green to olive green above and white underneath, simple, and alternately arranged, with one leaf per node along the stem. Each leaf is heart shaped at the base, hence the specific epithet, cordata, and can be 8-12” wide. Flowers bloom along tall, erect stalks from mid to late summer, typically in July and August. Each flower has 24-30 conspicuous stamens, and stems containing a (toxic) yellow sap. The fruit is a dry capsule that splits open when ripe. 

Until the early part of the 20th century, the plume poppy (herbaceous) plant was included in the genus Bocconia, a group of woody members of the poppy family. Later, the two herbaceous members of the poppy family (M. cordata and M. microcarpa) were moved into the genus Macleaya, and later hybridized as a third species cultivar of the two, Macleaya x kewensis.  Macleaya cordata is often confused for its relative, Bocconia frutescens, another invasive plant species in the Papaveraceae family commonly referred to as the plume poppy, and previously misunderstood to be a synonymous species. M. cordata is native to Japan, eastern China and Taiwan, while B. frutescens is native to much of the Americas, including parts of Mexico, Central and South America. 

Macleaya cordata is generally considered more invasive in Europe and North America, while Bocconia frutescens is particularly problematic in certain areas like Hawaii and Australia, where it was not known to be native and spreads aggressively and rapidly, making it a more significant invasive species issue in those specific regions. Both species spread readily through seed dispersal, but M. cordata can also spread through rhizomes, which can make it more aggressive in certain environments. In addition, both plants can outcompete native vegetation due to their rapid growth and ability to form dense stands, but the severity of their impact can vary depending on the local ecosystem. 

Damage & Concern

Plume poppy can spread quickly via self seeding and aggressively by rhizomes, especially in moist, fertile soils, and appears to thrive in a shaded environment. The species can become difficult to remove, as rhizomatous roots travel underground and become more established. Plume poppy rapidly forms large clumps and dense stands, and has the potential to overtake certain ecosystems, effectively crowding out and competing with surrounding native vegetation. 

Despite being used medicinally, there is a toxic alkaloid known as sanguinarine in the plant’s yellow inner stem sap. The compound is toxic to humans and animals, resulting in aggravated stomach upset in humans if ingested, and more serious and potentially fatal conditions in dogs, cats, horses and livestock.

Management & Control

In managing and controlling plume poppy, the primary focus should be on preventing its spread. This can be accomplished through early detection and rapid response, by regularly monitoring areas where the plant may be present, and removing the plants as soon as they are observed, to prevent seed production and further spread. 

Manual removal of plants can be accomplished by hand-pulling or digging up the root system, taking caution to remove all root fragments, as plume poppy is known to propagate itself via root fragments. If hand-pulling or digging is not an immediate option, removing and cutting back seed heads prior to seed dispersal is another option, as the plant spreads vigorously through self seeding capabilities; however, this will not stop rhizomatous shoots from appearing regardless. It is important to be aware that seeds can be easily dispersed by wind, so take precautions to prevent further spread during removal. Plume poppy contains toxic compounds, so wear gloves and protective clothing when handling the plant. 

Additionally, physical barriers such as edging to limit its spread in gardens or natural areas could assist with containment depending on the site location. A more natural approach may be considered through planting selection, utilizing companion plants or native plants in cultivated settings that can help to naturally compete with the plume poppy to potentially prevent its spread. 

In some cases, herbicides can be another viable option, but should be applied with caution and according to label instructions, as they may impact non-target plants. To control plume poppy, herbicides containing glyphosate are generally the most effective option, as it is a systemic herbicide that can kill the entire plant, including the root system. The best approach in herbicide application would be a foliar hand wiping method, or direct stem injection, as opposed to a broadcast application. For best results, apply the herbicide when the plant is actively growing, typically in the earlier stages of development. Always be sure to follow all label directions and abide by local regulations when using all chemical treatments.  

Monitoring & Reporting 

LIISMA is actively monitoring plume poppy in priority conservation areas and beyond due to its status as a significant concern for invasive species management. This species is prioritized for early detection and rapid response. As reports are gathered, LIISMA collaborates with partners and landowners to identify and manage early infestations before they can spread widely. Plume poppy is classified as a Tier 2 invasive species on Long Island, emphasizing the need for timely action. LIISMA encourages the public to report any sightings of this species.

Your reports matter to us–report the species to iMapinvasives or iNaturalist as soon as you detect it!

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