Stachytarpheta urticifolia
(rattail)

Preferred Common Name

• rattail

Other Scientific Names

• Cymburus urticaefolius Salisb., nom. illegit.
• Zappania urticifolia (Sims) Poir.

International Common Names

• English: blue rat’s tail

Local Common Names

• Bangladesh: nilkanthi
• Fiji: finak ne puak; sere
• India: tharoi-phijup
• Tokelau: mautofu
• Tonga: hiku 'i kuma

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Lamiales
•                         Family: Verbenaceae
•                             Genus: Stachytarpheta
•                                 Species: Stachytarpheta urticifolia

Stachytarpheta is a genus of about 133 species in the Verbenaceae, distributed mainly in tropical America (Atkins, 2005). Stachytarpheta urticifolia was described by John Sims in 1816 from plants cultivated in London by John Walker (Sims, 1816). The original provenance of Walker’s plants were unknown. The validity of this species has been controversial, complicated by the lack of a type specimen (Munir, 1992; Chen and Wu, 2003). As the type specimen cannot be found the species was lectotypified by Daniel and Rajendran (1992), designating the illustration in the original publication by Sims.

Some recent authors include S. urticifolia in synonymy of Stachytarpheta cayennensis, a native of tropical America (Munir, 1992; Wunderlin and Hansen, 2003). However, other authors recognize the species as distinct (Nicolson, 1991; Verdcourt, 1992; Chen and Wu, 2003; Devi, and Singh, 2005; Acevedo-Rodriguez and Strong, 2016). As discussed by Chandler et al. (2014), the taxonomy needs additional study. This problem is unlikely to be resolved until a comprehensive study is conducted of this and similar species.

Complicating matters further, the identification of S. cayennensis, Stachytarpheta indica, and Stachytarphetajamaicensis species has been problematic on a global scale. Confusion and misidentification of these species in the literature is rampant. For example, Chen and Wu (2003) found that in Taiwan nearly all reports of S. jamaicensis represented S. urticifolia and considered the name S. cayennensis to be misapplied to S. jamaicensis. In India Rajendran and Daniel (1992) found the name S. indica to be misapplied to both S. urticifolia and S. jamaicensis.

For the purposes of this datasheet S. urticifolia is treated as a valid species,  following Verdcourt (1992), Chen and Wu (2003), and Devi and Singh (2005). Most distributional data presented here is tentative. Unravelling literature reports and clarifying global ranges of S. urticifolia, S. cayennenis, S. jamaicensis, and S. indica will be impossible until species concepts are resolved, and specimens then examined through the ranges of each taxon.

Some authors have used the spelling S. urticaefolia rather than S. urticifolia, and have also attributed the authorship to Salisbury (e.g. as S.urticaefolia (Salisbury) Sims). Sims (1816) clearly spells his new epithet as “urticifolia”, but refers to an earlier name by Salisbury: Cymburus urticaefolius. As has been discussed by Nicolson (1991) and Verdcourt (1992), the Salisbury name is illegitimate and excluded from synonymy by Sims. Thus, the proper spelling and authorship of the species is S. urticifolia Sims. 

The following is adapted from Chen and Wu (2003).

Perennial semi-woody herb; weakly erect, 80-200 cm tall, the stem or branches dichotomous, 4-angled, dark green flushed with purple. Leaves opposite, membranous; blade ovate to broadly elliptic, 5-8 cm long, 3-6 cm wide, bullate above, obtuse or abruptly acute apically, coarsely serrate with sharp outward-pointing teeth, cuneately narrowed basally, petiole 0.5-2 cm long. Spikes terminal, flexible during anthesis, 25-40 cm long, 3 mm in diameter. Flowers sessile, 3-5 flowers open at a time; calyx tubular, compressed, 5-6 mm long; corolla salverform, dark purple-blue, with a white eye at the base of upper lip, 8-9 mm long, perfect stamens 2, filament 1.2 mm long and 0.3 mm wide, anthers light yellow; stamens included; style elongated, exerted, 7 mm long, white flushed with purple. Fruit enclosed by the persistent calyx, black, oblong and compressed, 4 mm long and 1.5 mm wide; seed closely enclosed by the thin pericarp.

S. urticifolia was in cultivation as early as the early 1800s in London, UK (Sims, 1816). Its early use as a garden plant had led to an obscure native range, and to the global spread of the species. It was introduced to Taiwan by 1925 as an ornamental (Chen and Wu, 2003), for example. It was first found in India between 2001 and 2004 (Devi and Singh, 2005). The dates of introduction to many parts of its range are unknown, in part, due to confusion in the literature between this and related species, a problem that will not be unraveled until these species receive a global taxonomic revision.

Soil drainage

• free

Soil texture

• light
• medium

Vector Transmission

While no reports have assessed any specific seed dispersal mechanisms of S. urticifolia, the very similar Stachytarpheta cayennensis is reported in Australia to be spread by attaching to animal fur and to machinery (Weeds of Australia, 2011).  

Accidental Introduction

S. cayennensis has also been documented as being dispersed through the dumping of landscape material and in contaminated soil so this may also be the case for S. urticifolia (Weeds of Australia, 2011).  

Intentional Introduction

S. urticifolia has spread outside of its native range through its use as an ornamental. It was cultivated in England by the early 1800s (Sims, 1816).

Impact on Habitats

S. urticifolia is a weed of disturbed areas, moist deciduous forests, beaches, brushland and grassland. It has the ability to compete with native species where it becomes established. For example, in the Ogasawara Islands, Japan, it invades disturbed areas and prevents the regeneration of native species by disrupting successional processes (Abe et al., 2014).

Impact on Biodiversity

S. urticifolia has allelopathic properties (Kuo, 2003). When the species escapes it can effectively outcompete desirable native species. S. urticifolia may impact rare and endangered species, but this has not been accurately evaluated. In Hawaii it has been listed as impacting the subshrub Schiedea spergulina var. leiopoda (USFWS, 2010). However, while S. urticifolia has been reported for Hawaii (Wagner et al., 1999), more recently the populations of Stachytarpheta formerly called S. urticifolia in the Hawaiian archipelago have been considered to represent S. cayennensis (Wagner and Herbst, 2003). 

• Invasive in its native range
• Proved invasive outside its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Pioneering in disturbed areas
• Benefits from human association (i.e. it is a human commensal)
• Fast growing
• Has high reproductive potential
• Reproduces asexually

• Ecosystem change/ habitat alteration
• Reduced native biodiversity
• Threat to/ loss of native species

• Allelopathic
• Competition - monopolizing resources

• Highly likely to be transported internationally deliberately
• Difficult to identify/detect as a commodity contaminant

Economic Value

The primary economic value of S. urticifolia is as an ornamental species. Due to its attractive blue flowers, which attract a diversity of pollinators, it is grown in tropical regions. Plants are sold in nurseries and seeds are sold on the Internet.

Social Benefit

Stachytarpheta species are often used as traditional medicines. In Bangladesh S. urticifolia has been used as a anthelmintic, abortifacient and used traditionally in venereal diseases, ulcers, dropsy, fevers, stomach troubles and rheumatic inflammations. An infusion of bark is used in treating diarrhea and dysentery (Chowdhury et al., 2004).