Taxonomic name: Vitex rotundifolia L.f.
Synonyms: Vitex agnus-castus var. ovata (Thunb.) Makino, Vitex ovata (Thunb.), Vitex repens Blanco, Vitex trifolia subsp. litoralis Steenis, Vitex trifolia var. obovata Bentham, Vitex trifolia var. ovata (Thunb.) Makino, Vitex trifolia var. ovata (Thunb.) Merrill, Vitex trifolia var. repens Ridley, Vitex trifolia var. simplicifolia (Cham.), Vitex trifolia var. unifoliata Schauer
Common names: beach vitex (English), chasteberry, cloister pepper, dan ye man jing (Chinese-China), hamago (Japan), hinahina kolo (Hawaiian-Hawaii), kolokolo kahakai (Hawaiian-Hawaii), man hyung ja (Korea), manawanawa (Hawaiian-Hawaii), mawanawana (Hawaiian-Hawaii), monk's pepper, pohinahina (Hawaiian-Hawaii), polinalina (Hawaiian-Hawaii), roundleaf chastetree, single-leaf chaste tree
Organism type: shrub
Vitex rotundifolia, also commonly known as beach vitex, is a perennial woody shrub of coastal sand dunes of Asia and the Pacific islands. It has been introduced into the United States where it is an invasive exotic plant. Vitex rotundifolia has a strong impact on the native flora and fauna along the United States Carolina coast, shading native plants and disrupting nesting sites for sea turtles. Active community involvement and strategic mapping and eradication efforts are underway to limit the extent and impact that this exotic species has on the coasts of the Carolinas and prevent it from spreading into a wider geographical range.
Vitex rotundifolia is a branched deciduous shrub (Westbrooks and Brabson, 2007) that can reach heights between 0.5-1 metres and have horizontal growth up to 20m long, but more commonly has a width around 5 metres (GRI, 2006). According to Westbrooks and Brabson (2007), the "branchlets are obscurely tetrangular, tomentose, stems procumbent, often rooting at the nodes, forming mats several metres in diameter, 1-3dm long". The leaves are simple obovate to suborbicular, 2-6.5cm long, 1-4.5cm wide, and an acute base. The upper surface of the leaf is pale green and densely puberulent with a greyish-white lower surface. The lower surface of the leaf is also densely tomentose, short petiolate, and apex rounded (Westbrooks and Brabson, 2007). The foliage has a spicy fragrance when crushed (HNPPD, 2001). The flowers are arranged in terminal clusters in panicles, and about 2cm long (Gresham & Neal, undated; HNPPD, 2001). The corolla is bluish-purple, densely puberulent externally, with the tube about 8mm long. The upper two lobes are 3.5mm long with the margins recurved. The lateral lobe is about 4mm long and the lower lobe is about 7mm long. The base of the lower lobe is marked by two white pilose. The stamen is esxerted from the corolla. The filaments are 9-10mm long and pilose at base. The style is also exserted from the corolla and is about 12mm long. The fruit consists of a dry, globose drupe, and is about 6mm in diameter. During September-October the fruit turns from green into yellow and red-tinged. At maturity the fruit is bluish-black (Westbrooks and Brabson, 2007).
Amaranthus pumilus, Cakile edentula ssp. harperi, Croton punctatus, Iva frutescens, Iva imbricata, Morella cerifera
Vitex rotundifolia is an obligate sand dune species (Kim, 2005). It is found at low elevations on beaches, sand dunes, and rocky shorelines (HNPPD, 2001). Beach vitex is highly salt and drought-tolerant (GRI, 2006) and grows best in full sun and sandy or well-drained soils (SCNPS, undated). . According to Madsen,et al, (2005), the plant can survive in five U.S. hardiness zones, which increases the likelihood that this plant may spread to a much wider climatic and geographical range in the United States than it currently occupies.
Vitex rotundifolia is considered an invasive species in the Carolinas and has the potential to spread to many more coastal communities along the shores of the United States (Madsen,et al, 2005). Beach vitex is a rapidly growing and sprawling shrub both vertically and horizontally that is very tolerant of salt and drought (Gresham & Neal, undated). Beach vitex produces a large seed bank and can reproduce vegetatively through rooting at leaf nodes along runners (Gresham & Neal, undated). The impact of its aggressive growth pattern leads to little light reaching the soil surface where it dominates as monocultures preventing native species from establishing (Gresham & Neal, undated). In addition it has been suggested from scientific observations that the plant releases some allelopathic compounds that have actions in the soil to make it hydrophobic, causing drought stress to less tolerant native species (Gresham & Neal, undated). The structure of the plant's root system does not make it an ideal dune stabiliser compared to fibrous root systems of native species causing higher rates of dune erosion (SCNPS, undated). It causes mortality in young sea turtles by entangling them in its long runners and impacts nesting sites for reproductive females (SCNPS, undated) (please see impact information in the North and South Carolina distribution records). Beach vitex also impacts multi-million dollar beach renourishment projects (Madsen,et al, 2005).
Vitex was historically used to suppress sexual desire in women and for similar reasons became a culinary spice in monasteries, hence the common name Monk's pepper (SCNPS, undated). Some of the active chemical compounds in the plant have been linked to female hormone balance, female reproductive organs, menopause, actions on the pituitary gland, and treatment for acne (SCNPS, undated). Compounds in the plant have also been linked to inhibit lung and colon cancers (Gresham & Neal, undated). The plant was originally introduced as an erosion control and ornamental in the United States, however its negative effects on coastal species communities does not favour it for this use (SCNPS, undated). In its native range this plant makes an excellent ground cover, ornamental, and sand dune restoration plant (HNPPD, 2001). In Hawaii the flowers and seeds of the plant are used in the making of leis (HNPDD, 2001). In Japan V. rotundifolia is used as a cold and headache remedy. In Korea the fruit has also been used for the relief of headches caused by upper respiratory infection. Also in Korea it has been used for the rehabilitation and landscaping in seaboard areas (Westbrooks and Brabson, 2007).
Vitex rotundifolia was introduced to the southeastern United States from Korea by North Carolina State University Arboretum in the mid-1980s. It was introduced for the purpose of dune stabilisation and for ornamental use. The fruit of V. rotundifolia contains compounds that inhibit lung and colon cancer cells (Westbrooks and Brabson, 2007). According to Westbrooks and Brabson (2007), "beach vitex meets the definition of a quarantine significant pest because it occupies a very small portion of its potential ecological range in mainland United States, and because it poses a serious threat to certain natural and biological resources (the stability of ocean front dunes and the plant and animal communities that occupy them), as well as the value of beachfront property. The pest risk potential of beach vitex listed as medium-high. Since the plant was intentionally introduced the likelihood of introduction is high. Consequences of introduction are medium due to low economic impact and serious environmental impacts (Westbrooks and Brabson, 2007).
Native range: China, Japan, India, Sri Lanka, South Korea, Malaysia, Australia, Taiwan, Thailand, Indonesia, Fiji, New Caledonia, Philippines, Papua New Guinea, Mauritius, Hawaii (US) (USDA-GRIN, 2007; Gresham & Neal, undated; Kim, 2004)
Known introduced range:North Carolina, South Carolina, Florida, Alabama (Sea Grant NC, 2006; NERR, undated).
Introduction pathways to new locations
Floating vegetation/debris: Vitex rotundifolia stems are brittle and can be broken apart and carried away in ocean waves and high tides to new locations where they can reroot (GRI, 2006).
For ornamental purposes: Vitex rotundifolia was introduced into the United States partly as an ornamental plant (Madsen,et al, 2005) and is still being sold in nurseries in Texas, Virginia, and Alabama (SCNPS, undated).
Landscape/fauna "improvement": Beach vitex was mainly introduced into the United States for dune stabilization and coastal erosion control (Madsen,et al, 2005).
Local dispersal methods
Consumption/excretion: The seeds of beach vitex are consumed by birds and can be carried long distances and excreted in new locations (FWS, undated).
For ornamental purposes (local): Spread of beach vitex can continue if it is still used by the public as an ornamental in residential settings (Madsen,et al, 2005).
Water currents: The seeds and runners of beach vitex are spread by water currents and high tides to new locations (Madsen,et al, 2005).
Preventative measures Currently federal, state, and local government, academic and non-profit organisations are attempting to get Vitex rotundifolia listed as a Federal Noxious Weed which would prohibit the sale and transport of the species in the country unless with a permit (Madsen,et al, 2005). Getting the species listed would also help promote eradication programmes and monitoring of new populations if they arise (Madsen,et al, 2005). Other measures that have been in effect are publications through non-profits, cooperative extensions, and government agencies on identification and how the public can report sightings and locations of populations (Sea Grant NC, 2006).
Physical Hand-pulling, digging, and the use of machinery are all options that can be used to remove beach vitex, however due to the fragile nature of the dunes and the risk of erosion these methods should be used with caution (Gresham & Neal, undated; SCNPS, undated). Any mechanical methods to remove the plant should be thorough to make sure that the root ball or any stem fragments are not left behind to reestablish (Sea Grant NC, 2006). Mechanical methods to reduce the seed and stem fragments from spreading are to clip any flowering or fruiting stems and gently remove any long seaward runners (FWS, undated). Any beach vitex plant material should be sealed in plastic bags and taken to a landfill rather than mulched or composted as plant parts can reestablish(FSW, undated).
Chemical Several different techniques of herbicide application are being tested on beach vitex. Three different techniques can be used to apply a herbicide to the plant. One method is to cut the aboveground vegetation back to a stump and then apply a glyphosate paint to the exposed cut (Sea Grant NC, 2006; Grisham, undated). The second method is to wound the stem and then apply a herbicide to the wound (Sea Grant NC, 2006). The third method is to apply an oil based herbicide mixture to the stem in a 30-45cm length band at the base of the stem (Sea Grant NC, 2006). Herbicides should be selected carefully and used with caution as well as in appropiate amounts due to the sensitivity of the area and its proximity to the ocean (Sea Grant NC, 2006).
Cultural Revegetation with native grass and dune species should be incorporated into any control program to prevent erosion and recolonization (Gresham, undated).
Vitex rotundifolia reproduces by seed and vegetatively. The plant is a prolific seed producer with estimated seed crops of 22,000 seed/square metres, with field tests resulting in 30% germination (Gresham & Neal, undated). Beach vitex can spread vegetatively through rooting at leaf nodes along runners that can reach lengths of up to 20 metres (GRI, 2006). The seed can be spread by birds eating the fruits while both the seed and stem fragments are dispersed by waves and high tides (GRI, 2006, FWS, undated).
Beach vitex flowers in May in the Carolinas (Gresham, undated), but can produce flowers throughout the year in Hawaii (HNPPD, 2001). The fruits ripen and dry in the summer while the leaves begin to dry and fall off in autumn, leaving a mat of tangled stems throughout the winter(Gresham, undated). The fruits are persistent on the plant in clusters (Gresham, undated). Seed germination takes up to 3-6 months (HNPPD, 2001).
Reviewed by: Expert review underway: Dr. Randy G. Westbrooks
Whiteville, North Carolina
Principal sources: Gresham, C.A., & Neal, A., undated, An Evaluation of the Invasive Potential of Beach Vitex (Vitex rotundifolia)
Madsen, J.D., Abbott, C., Brown, R., Bruce, L., Byrd, Jr., J., Dibble, E., Ervin, G., Fowler, J., Maddox, V., & Shaw, D., Dec. 2005, Research to Support Integrated Management Systems of Aquatic and Terrestrial Invasive Species, Annual Report Mississippi State University GeoResources Institute in collaboration with United States Geological Survey
Sea Grant North Carolina, 2006, Beach Vitex: Kudzu of the Coast?, Coastwatch Spring 2006, National Sea Grant College Program.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Monday, 14 May 2007