Beach vitex is scientifically known as Vitex rotundifolia. The scientific name is Latin meaning round leaf. This refers to the round shape of the leaves. It is also known as monks pepper, single leaf chaste tree, chasteberry, and round-leaved chaste tree. This plant can withstand salty waters. It is a perennial shrub that has invaded and naturalized the areas along the beach. This plant is a known invasive, and in this article we will talk about how to remove beach vitex.
Chasteberry was introduced in the 1980s with hopes that it would stabilize coastal dunes. It was planted in the coastal area of North Carolina as an ornamental plant for coastal families. This plant is originally from Asia, Japan. It grows on the sandy beach soil of the coastline where there is intense heat and strong winds. The coastal conditions allow it to grow quickly and choke out other slow-growing native plants.
How to identify beach vitex
This plant is non-native, with woody shrubs. It grows about one-meter tall running through the soil as it forms patches. In a year the long runners can grow up to ten feet creeping over the dunes.
The round leaves grow up to 1.5 inches in diameter. The leaves are in pairs along the woody stem. The majority of leaves are simple, but they can occasionally be palmate, trifoliate or two-leaved. Margins of the leaf are smooth and entire. In November, the leaves turn white and drop off in December. When crushed, the green leaf has a spicy fragrance.
In May, the plants produce a cluster of purple flowers and ultimately yield small brown-black fruits on a stalk at the tip of the shoot. The upper part of the plant has stalks that hold approximately 50 flowers. The stalks deep in the canopy have less than 10 flowers. The flowers drop giving rise to the drupe which is green and round. This drupe has a diameter ranging between 1/8 to ¼ inch wide. When the drupe has dried it changes its color to black. It has between two to four seeds that germinate into seedlings. These seedlings carry two cotyledons.
New stems are green, square and fleshy initially before maturing into brown and woody. The older stems have a wide diameter covered with a narrow rough bark. Running horizontal stems produce frequent upright branches.
It has a non-fibrous root system. The stolons develop secondary roots, which can form smaller deep root systems, and the entire maze grows very quickly in the summer. It produces runners that root regularly at nodes. The roots have a pattern that enhances the rapid spread of the plant.
Vitex rotundifolia.
Natural habitat
Vitex rotundifolia is an obligate dune species. It is found at low elevations on beaches, dunes, and rocky shorelines up to fifty feet above sea level. It is highly salt and drought-tolerant and grows best in full sun and sandy or well-drained soils.
The plant can survive in hardy areas, which increases the likelihood that this plant may spread to a much wider climatic and geographical range than it currently occupies. Globally, it is present in both tropical (where it is evergreen) and temperate (deciduous) climatic regions.
Medicinal and food value of beach vitex
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. Compounds in the plant have also been linked to inhibiting lung and colon cancers.
Other uses
In its native range, this plant makes an excellent ground cover, ornamental, and dune restoration plant. The flowers and seeds of beach vitex are used to make garland or wreath in Hawaii. In Japan, it is used as a cold and headache remedy. In Korea, the fruit has been used for the relief of headaches caused by an upper respiratory infection. Also, it has been used for the rehabilitation and landscaping in seaboard areas as well as culinary spice in monasteries.
Why is beach vitex invasive?
For a foreign species to invade a new area three factors must take place: the species must reach and be distributed in the new area, and the plant materials used in reproduction must also reach the region. Beach vitex being the only plant growing, replaces the indigenous species through runners and pollination of the flowers.
Fruits are capable of water-based dispersal, allowing for a potential rapid range of expansion in coastal areas. It’s a prolific seed producer. The seeds float and can be carried to other beaches. These seeds and cuttings that are chipped up and spread as mulch may start new populations. The brittle stems break off during high tides, float away, root and colonize other beaches. Therefore it is important to remove beach vitex.
Insect pollination is the likely method of pollen transfer due to the special separation of the anthers and stigmas, which would make self-pollination unlikely. Flies, butterflies, and ants make a diverse group of pollinators in search of nectar. Pollinator activity is variable from year to year but consistent with increased fruit and seed set.
This plant is drought and salt tolerant which allows it to withstand the harsh coastal conditions. The conditions are favorable for its fast growth making it spread extensively along the beaches. Birds eat seeds and aid in distribution.
Beach vitex invasion. Image by Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Why you should remove beach vitex
The plant robs other vegetation of the sunlight and essential nutrients. This shade and perhaps some other growth characteristics kill shorter beach plants and prevent seedlings of native species from establishment. The wax that comes off the leaves and fruit causes the sand to repel water. Beach vitex causes problems for sea turtles. The plant grows over the fore-dune, blocking access for nesting. It grows so aggressively that during the 60-day incubation time many turtle nests are overgrown, entrapping the hatchlings. Some have been found dead, entangled within the rhizome mats.
Beach vitex forms thick leaves and stems on the dunes and beaches contributing to a decrease in nesting by sea turtles. Female sea turtles seek an open beach area to dig a nest and will not attempt to dig in an area with a thick vegetative cover. This plant spreads on beaches crowding out native species like sea oats.
Its stems can cover 100% of the dune and this heavy cover creates a deep shade that only allows less than 5% sunlight, which prevents seedlings of other species from emerging.
Seabeach amaranth which is responsive to perennial covers faces extinction as a result of beach vitex. This indigenous plant is rare and is found where water and sediments flow in the dunes. The plant does well in areas where other plants have not grown. Due to this reason, seabeach amaranth can’t grow in an area that has beach vitex.
This plant releases allelopathic compounds from the root system that decrease the growth of other seedlings. Soil below some of its population is strongly hydrophobic preventing the survival of a newly germinated seed of a different species.
How to Remove Beach Vitex
Ecological concerns surrounding its presence along the coast have necessitated the development of effective control methods. Beach vitex grows fast, spreading extensively along the beach. Complete eradication is important to protect other species from eradication. This will also enhance the life of sea turtles that have been blocked from accessing their nesting.
Eradication requires constant application of control methods since it has a high reemergence rate. Where it may be required for medicinal purposes and other uses, it should be regulated within defined areas. This will restrict it from spreading extensively to other areas along the beach.
This plant can be controlled through plastic films such as black polythene sheeting that are considered mulch for invasive plant control by absorbing most ultraviolet, visible and infrared wavelengths. They can be used to suppress invasive growth. Methods to remove beach vitex include mechanical removal that involves cutting and burning, and chemical that involves the use of herbicides.
Mechanical removal
These physical methods involve cutting the stems just above the groundline. Most beach vitex stems can be cut with lopping shears. However, larger stems may require a saw. Cut material should be taken to a compost facility for proper disposal or piled on a concrete surface until the leaves drop off, then composted.
Manual removal is best suited for smaller plants with a shallow root system that is growing on loose soil. As such, manual removal is expensive and time-consuming but can be used as a component of invasive plant control. This process alone is ineffective due to a significant quantity of rooted underground stems that are capable of rapid regeneration.
Hand pulling or grubbing is often the quickest and easiest way to remove beach vitex when first spotted and can be a very effective. However, roots break off during extraction resulting in regeneration. Manual removal can also cause unwanted soil disturbance which can result in conditions favorable for reinvasion.
Pruning shears are required when mechanically controlling climbing vines or small multi-stemmed woody species. This is done by following the vine or stem to the point where it emerges from the ground. If unable to unearth the stem, it is advisable to cut as close to the ground as possible and remove debris.
Mulching machines are best used in nonselective scenarios where the cost of selective control is far too prohibitive and may result in non-action for the project. Mulching machines are land clearing tools that can cut through dense stands of invasive plants.
Burning can be used as a management mechanism. It should be done by a specialist for safety measures. This is effective during the early stages of growth between September and December.
Biological removal
No biological control systems are known to remove beach vitex. Chemicals produced by these plants help it resist attack from insects. Shrubs are prone to ants, scale, aphids, mealy bugs, and spittlebugs. In the rainy season, rot fungi show up but disappear during drought.
Chemical removal
The most effective method to remove beach vitex over a wide area is the use of herbicides. The stems are cut with blades to expose cambial layers. Then, apply herbicides on the cut surface. After six months, you should remove all visible plant parts from the sites and plant noninvasive beach plants.
Any regrowth is treated in the same way as before. You repeat the process until the site has zero regrowth. Control studies of the plant have indicated that multiple seasons of retreatment may be required for successful eradication. Additionally, you should take care to avoid secondary infestations from other invasive plants such as smilax spa following beach vitex removal.
Spraying of herbicides is suitable where the plant is dense and without other vegetation. This is because the herbicide may end up killing other organisms such as sea oats. This method of control can cover a wide area as compared to uprooting and using hand clippers.
It is advisable to spray in times when there is no wind. Early mornings are usually the only time the winds are light enough to spray. If you do spray during windy conditions, you risk damaging other nearby desirable plants with any herbicide that blows onto their leaves.
Watch treated plants for signs of dieback. If after six to eight weeks plants are thriving, you may want to make another application of the herbicide. It is advisable to use chemical removal on beach vitex during the growing stage between April and November. There is no need to apply herbicides when the plants are not actively growing.
If you notice sprouts, you should recut them to expose a fresh surface and reapply the herbicide solution. Be sure to wear personal protective equipment (long pants, long sleeves, gloves and safety glasses) when applying herbicides.
Conclusion
The fast-growing characteristics of beach vitex aid in its extensive growth along the beach. Insects are the main agents of pollination while the birds and water help in the distribution of the seeds.
Medicinal value necessitates the need for the plant. In areas where it’s planted, there is a need to control its growth due to its invasive nature. Maximizing the use of manual control methods with the added benefit of selective herbicide treatments can offer the best results in many situations as a control mechanism.
References
- Barrier Island Ecology: Beach Vitex https://sites.google.com/site/barrierislandecology2013/terrestrial-flora/beach-vitex
- United States department of agriculture: New invaders of the southeast https://bugwoodcloud.org/resource/pdf/FHTET-2017-05_New%20Invaders_SE.pdf
- Beach vitex invades the Carolina coast https://www.fws.gov/nc-es/port/BeachVitexposter.pdf
- University of Florida: is beach vitex a growing problem http://nwdistrict.ifas.ufl.edu/nat/2013/07/20/beach-vitex-is-it-a-growing-problem/
- Mississippi State University https://www.gri.msstate.edu/research/ipams/FactSheets/Beach_vitex.pdf
- Beach vitex eradication https://www.emeraldisle-nc.org/Data/Sites/1/media/pdfs/beachvitextreatmenthomegardener.pdf
