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Phytolacca americana

Large herb, up to 3 m, and quadrangular stems, frequently reddish, and with black berries.

Scientific name: Phytolacca americana L.

Common names: pokeweed, American pokeweed, pokeberry

Family: Phytolaccaceae

Status in Portugal: invasive species (listed in the Decreto-Lei nº 92/2019, 10 july)

Risk Assessment score: 29 | Value obtained according to a protocol adapted from the Australian Weed Risk Assessment (Pheloung et al. 1999), by Morais et al. (2017), according to which values above 13 mean that the species has risk of having invasive behavior in the Portuguese territory | Updated on 30/09/2017.

Synonymy: Phytolacca decandra L., Phytolacca vulgaris Crantz

Last update: 11/07/2021

Family: 
Phytolaccaceae
Appearence: 
Grasses and herbs

How to recognise it

Large herb up to 3 m, ramified, sometimes woody on the base. Quadrangular stems, green, red or purple.

Leaves: simple, with 12-25 x 5-10 cm, ovate–lanceolate or ovate-elliptic.

Flowers: white or pink, with similar tepals, forming a long raceme (up to 30 cm) ± erect, 10 stamens.

Fruits: purple-black berries, composed of 10 fused segments in a ring, making the stem hang in maturation.

Flowering: May to December.

 

Similar species

Phytolacca heterotepala Walter, also exotic, and normally found in the surroundings of Coimbra and Lisbon, is similar but it is a  shrub (or a small shrub) and it presents unequal tepals (the exterior narrower that the rest) and more stamens (9-21).

 

Characteristics that aid invasion

It propagates by seed, producing more seeds which are dispersed by birds.

It also propagates vegetatively by sprouts from the roots.

Native distribution area

North America.

 

Distribution in Portugal

Mainland Portugal (Minho, Trás-os-Montes, Douro Litoral, Beira Litoral, Beira Alta, Beira Baixa, Estremadura, Ribatejo, Alto Alentejo, Algarve), Azores archipelago (all islands), Madeira archipelago (Madeira island).

 

Geographic areas where there are records of Phytolacca americana

Other places where the species is invasive

Invasive in several European countries, western USA (California).

 

Introduction reasons

For medicinal purposes and use in dyeing.

 

Preferential invasion environments

Ruderal and disturbed habitats, crop fields and roadsides. It also invades semi-natural habitats.

Impacts on ecossystems

It inhibits the development of native vegetation.

It has allelopathic effects, inhibiting the development of other species.

 

Economic impacts

It causes important damages in agricultural areas.

 

Other impacts

Some parts of the plant (stems, leaves, fruits) are toxic, being noxious for animals.

Controlling an invasive species demands a well-planned management, which includes the determination of the invaded area, identifying the causes of invasion, assessing the impacts, defining the intervention priorities, selecting the adequate control methodologies and their application. Afterwards it is fundamental to monitor the efficiency of the methodologies and recuperation of the intervened area as to perform, whenever necessary, the follow-up control.

The control methodologies used for Phytolacca americana include:

 

Physical control

Hand pulling (preferencial methodology). In more compacted substrates, hand pulling must be made during the rainy as to facilitate the removal of the root system. As much as possible, it should be guaranteed that there are no large roots left in the ground.

 

Chemical control

Foliar application of herbicide. Spray with herbicide (active substance: glyphosate,  2,4-D) limiting its application to the target species.

 

Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.

DAISIE European invasive">Invasive Alien species">Species Gateway (2012) Phytolacca americana. Available: http://www.europe-aliens.org/speciesFactsheet.do?speciesId=8642 [Retrieved 10/11/2012].

 

 

Dufour-Dror J-M (2012) Alien invasive plants in Israel. The Middle East Nature Conservation Promotion Association, Ahva, Jerusalem, 213pp.

 

 

 

 

Fagundes D, Az J, Beiras MB (2007) Plantas invasoras de Galicia. Bioloxía, distribución e métodos de control. Xunta de Galicia, Santiago de Compostela, 209pp.

 

 

 

 

Marchante E, Freitas H, Marchante H (2008) Guia prático para a identificação de plantas invasoras de Portugal Continental. Imprensa da Universidade de Coimbra, Coimbra, 183pp.

 

 

 

 

Silva L, Corvelo R, Moura M, Land EO, Jardim R (2008) Phytolacca americana L. In: Silva L, Land EO, Luengo JLR (eds) Flora e fauna terrestre invasora na Macaronésia. Top 100 nos Açores, Madeira e Canárias. Arena, Ponta Delgada, pp. 370-372.

 

 

 

 

USDA, NRCS. (2012) The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.  Available: http://plants.usda.gov [Retrieved 10/11/2012].