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EDRR Invasive Species of the Month – Beach Vitex

EDRR Invasive Species

Beach Vitex (Vitex rotundfolia)

The radiating runners of beach vitex expanding over a sand dune on Pensacola Beach.
Photo: Rick O’Connor

 

Define Invasive Species: must have ALL of the following –

  • Is non-native to the area, in our case northwest Florida
  • Introduced by humans, whether intentional or accidental
  • Causing either an environmental or economic problem, possibly both

Define EDRR Species: Early Detection Rapid Response.  These are species that are either –

  • Not currently in the area, in our case the Six Rivers CISMA, but a potential threat
  • In the area but in small numbers and could be eradicated

Native Range:

Beach vitex is native to the coastal shores of Asian countries bordering the Pacific rim.  It is also found in Hawaii.

 

Introduction:

There are conflicting records as to when it was first introduced to the U.S.  One record has it in the country as early as the 1950s.  However, there are no records of plants from that stock still existing.  Most records suggest the release of the plant occurred in the 1980s when it was brought to North Carolina as a potential ornamental plant.  It was then used in dune restoration after a series of hurricanes and became a problem.  Thus, it was intentionally introduced.

 

EDDMapS currently list 649 records of beach vitex.  Most are in North Carolina.  There are 82 records in Florida and 46 (56%) are in the Pensacola Bay area.  We currently have 75 records from the Pensacola Bay area.  Not all are reported on EDDMapS due to private property restrictions.  Records do occur in coastal Alabama, Mississippi, as well as Okaloosa and Franklin counties in the Florida panhandle.

 

Distribution is most likely due to the high tolerance of salt water by the seeds and dispersal by currents, as well as intentional plantings by local landscapers and homeowners.  Vitex rotundifolia is now a noxious weed in Florida and can no longer be sold.

 

Within our CISMA there are records in all coastal counties (Baldwin, Escambia, Santa Rosa, and Okaloosa)

 

Description:

Beach vitex is a perennial plant that initiates from a main taproot and extends herbaceous vines across the surface of the substrate in almost a 360° pattern.  The vines can grow as much as 20 feet in length and become more woody with age.  As the plant grows, secondary roots extend from each of the nodes from the above ground stems (vines) and becomes more of a shrub, reaching a height of about two feet.

 

The two-inch leaves are ovate in shape, a light green to blue-green color, and are aligned opposite of each other.  They turn a reddish brown during the fall and winter and many plants will lose their leaves completely during this time.

 

The blossom is a lavender color and made of numerous small petals.  The blossoms are present during the spring and summer.  They will produce numerous charcoal gray fruits in fall and winter.  Each fruit can hold up to four seeds.  It has been reported that the plant can produce over 1000 seeds / m2.

 

Issues and Impacts:

After planting for dune restoration in North Carolina, the plant quickly became a monoculture.  It is allelopathic creating a hydrophobic situation in the soil.  This situation can cause the decline of native plants, such as sea oats (Uniola paniculata).  As the plant becomes more of a shrub it decreases the amount of sunlight reaching the surface further decreasing the smaller native plants and the ability for many to germinate.

 

This altering of the native dune plant community can have potential impacts on the native faunal communities.  There are concerns on its impacts to protected species such as beach mice and nesting sea turtles.

 

Having a taproot system rather than a fibrous one like the sea oat, can comprise dune integrity during tropical storms.  It is known that these dune systems provide protection for natural and developed areas behind them.

 

Management:

Finding the plants early and removing by hand is the first and best option.  The plant is relatively new to the panhandle area and smaller ones are often found.  Once the small plants are found, you can simply cut the above ground vine into 2 foot sections and place in a trash bag – you should double bag this.  Woody vines may puncture the bag so shorter sections may be needed for those.

 

Once you reach the taproot you may be able to pull it from the ground, or you may need to dig it out.  This method works well in loose dry sandy soils, it may require more digging and cutting if soils are more compacted.  If you cannot remove the entire taproot, we recommend spot spraying the remainder with glyphosate.  Be careful not to over spray, glyphosate is non-selective and will kill any native plants it comes into contact with.

 

In cases where the patch of vitex is too large to remove by hand then chemical treatment will be needed.  Several studies have been published as to which herbicides are effective.  Imazapyr, Triclopyr, and Glyphosate are all products that have been used both in foliage application and cut stem with success.  The exact concentrations vary with abundance of plants and surrounding habitats and re-treatments over a few years may be required.  We recommend you reach out to your local CISMA or county extension office for more direct help on your situation.

 

For more information on this EDRR species, contact your local extension office.

 

References

Invasive Species – Beach Vitex.  Rick O’Connor. 2017. UF IFAS Escambia County Blog.  http://blogs.ifas.ufl.edu/escambiaco/2017/03/20/invasive-species-beach-vitex/.

 

Early Detection and Distribution Mapping System (EDDMapS)

https://www.eddmaps.org/

 

Six Rivers CISMA

https://www.floridainvasives.org/sixrivers/