What is Beach Vitex?
Beach vitex (Vitex rotundifolia) is an exotic, deciduous, woody shrub that does not grow tall but forms thick patches by long runners at the soil surface. It is in the same genus as the commonly planted ornamental, chastetree (Vitex agnus-castus), and has flowers similar to those of the chastetree. The main difference between beach vitex and chastetree is that beach vitex, as the name implies, tolerates the harsh conditions of beach dunes. Beach vitex can tolerate droughty conditions of the sand dunes, can tolerate salt spray from the ocean and is not eaten by deer. Although beach vitex will also grow on the marsh side of barrier islands and coastal areas, it is not found in the tidal zone.
Do I Have Beach Vitex on My Property?
If you own beachfront property that was damaged by Hurricane Hugo in 1989 and planted the rebuilt dunes with species other than sea oats (Uniola paniculata) or American beach grass (Ammophila breviligulata), you could have planted beach vitex as many of your neighbors in the early 1990s. Beach vitex is woody, vine-like plant with almost round leaves (hence the specific name rotundifolia meaning round foliage) up to 1″ to 1.5″ in diameter, that are in pairs along the woody stem.
The leaves feel smooth like a fine leather or velvet. If you pick a green leaf and crush it you will smell a spicy fragrance. In May, the plants will produce a cluster of purple flowers on a stalk at the tip of the shoot. Stalks on the upper portions of the plant could have up to 50 flowers in the cluster and those deeper in the canopy could have less than ten.
When the flowers fall off, a green, hard, spherical fruit (drupe) between ⅛ inch and ¼ inch in diameter is left which gradually dries and turns black through summer. The fruit has one to four seed in each fruit. The leaves turn tan with white undersides in November and fall off in December. During the winter, beach vitex is a tangled mass of woody vine-like stems with clusters of hard, dry black fruits still attached.
Are There Other Beach Plants that Look Like Beach Vitex?
There are several woody plants that are native to our beach dunes that may at first look be confused with beach vitex, but a closer examination reveals clear differences.
Wax myrtle (Myrica cerifera) is a woody shrub that can grow to be a small tree, with the multiple stems and branches growing vertically. It is found landward of the front dunes and not on the front beach dunes. It is easy to identify because it is evergreen, the leaves are not in pairs on the twig, and the leaf length is at least 4 times the leaf width.
Sea rocket (Cakile harperi) is an herbaceous annual that grows in a small clump on the front beach. Sea rocket leaves are thick and not in pairs on an herbaceous stem. The plant forms a green, segmented, linear fruit in March and the terminal section will dry out and fall off during the summer.
Silver-leaf croton has oval-shaped leaves like beach vitex and may be thought to be a beach vitex seedling. But the leaves of silver-leaf croton are not in pairs, the leaves are on a longer stalk, the leaves and stems are covered with short fuzz and, with a 10X magnifying glass, you can see small brown dots on the bottom of the leaves. The silver-leaf croton plant is rarely 6 inches tall, has a bush growth habit, has slim branches, and does not have long shoots growing on the beach sand.
Seabeach amaranth (Amaranthus pumilus) is a federally threatened plant that is commonly found in wash-out areas between front dunes. The leaves look like spinach leaves, the stalks of the leaves are red, and its growth habit is of a small herb with a cluster of leaves. Because of its status as a threatened species, it is illegal to harvest or move the plant, so if you notice some of these plants, notify the property owner.
Seashore elder (Iva imbricata) is a woody shrub commonly found on front dunes and a nearly identical species, marsh elder (Iva frutescens) is found at the salt marsh edge. Seashore elder is a woody shrub, but the leaves are long and narrow and green on both sides. The length of seashore elder leaves is 4 times the width; compared to beach vitex leaves that are nearly as wide as long and seashore elder does not have a large round fruit like beach vitex.
Why the Concern About Beach Vitex?
The most apparent characteristics of beach vitex are the rapid growth of runners along the beach sand surface and the thick clumps it forms after a few years. Although it provides a vegetative cover for the dunes, it does so at the expense of the native dune vegetation. Beach vitex leaves and stems can cover 100% of the dune and this heavy cover creates a deep shade which allows less that 5% of the sunlight to reach the soil surface. This shade and perhaps some other growth characteristics, kills shorter beach plants and prevents seedlings of native species from becoming established. Research indicates that waxes come off of the leaves and fruit and cause the sand to repel water which also aids in preventing seedlings of other species from emerging.
The thick clump of stems and leaves formed by beach vitex on the front dunes and upper beach may contribute to the nesting decrease of the federally threatened loggerhead sea turtle in South Carolina. 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.
Seabeach amaranth is another federally threatened species and, like other native dune species, is sensitive to vegetative cover. Seabeach amaranth is rare and is found in an overwash between dunes where other vegetation has not established. Clearly, seabeach amaranth will not become established nor co-occur with beach vitex.
Recommendations if You Don’t Have Beach Vitex but Need to Plant Something on Your Front Dunes
Maintaining a vegetative cover on front dunes is strongly recommended but planting beach vitex on the front dunes is not only unwise but it is illegal. First, property owners should contact the Office of Coastal Resource Management (Charleston 843-744-5838; Beaufort 843-846-9400; Myrtle Beach 843-238-4528) to get a permit to plant on the front dunes. Once a permit is obtained, a planting of 70% sea oats (Uniola paniculata) and 30% bitter panicum (Panicum amarum) on an 18″ grid is recommended. Your county Extension Office can direct you to sources of seedlings for planting. Be sure the sea oat seedlings were raised from seed collected within 50 miles of your planting site; otherwise seedlings from out of state seed will not grow as well as plants from local seed. Sea oats should be planted in the spring and early summer, preferably following a rain to assure a moist soil. Healthy seedlings 15″ to 24″ tall should be planted at least 8″ deep; the deeper the better. Include in the bottom of each hole a tablespoon of time-release 18-6-12 fertilizer that can be obtained where ever hardware or plants are sold. Bitter panicum should be NRCS Accession Number PI421957, the ‘North Pa’ variety. Rooted cuttings are planted from April through September just like the sea oat seedlings. A few sweetgrass (Mulhenbergia filipes or M. capillaries) clumps can also be inter-planted among the sea oats and bitter panicum to add diversity. Sweetgrass should be planted landward of the front dune because it does not tolerate direct exposure to the salt spray.
Recommendations if You Have Beach Vitex and Want to Keep It
If beach vitex is growing on your property and you have decided that you wish to keep it, there are several things you need to consider. In general, realize that you have a fast growing exotic plant that has several undesirable characteristics as discussed above. Specifically, property owners need to first check with local town and county land use ordinances to make sure maintaining beach vitex is legal. If there are no ordinances prohibiting having beach vitex on your property, then the beach vitex should be kept trimmed at the property boundaries to make sure it does not grow on to adjacent lots, where it may not be wanted.
Likewise the beach vitex should be cut off the seaward face of the front dunes. Use hand clippers or lopping shears to cut the stems near the soil surface. The cut stems should then be taken to a county compost facility for proper disposal or piled on a concrete surface until the leaves drop off, then composted. Because of its rapid growth, the property lines and dune front face should be checked every other month from April through November for regrowth that should also be clipped.
Recommendations if You Have Beach Vitex and Want to Eradicate It
The easiest and safest way to eradicate beach vitex is a two step process involving cutting the stems just above groundline and immediately applying a Habitat (imazapyr) herbicide to the cut surface. Most beach vitex stems can be cut with lopping shears; however, the larger stems may require a limbing saw. Sections of the horizontal stems growing on the surface should be cut diagonally such that the cut surface is facing upward. On the front beach there may be a thick cover of small beach vitex stems, approximately ⅛ inch in diameter. These are easily cut with a gas powered string trimmer fitted with a sharpened triangular blade instead of the string head. Cut material should be taken to a county compost facility for proper disposal or piled on a concrete surface until the leaves drop off, then composted. As soon as possible after cutting, a 6 to 9% [8 to 12 oz/gal of Habitat (27.7% imazapyr)] solution with 1% blue dye and recommended surfactant in water should be mixed in a 5-gallon plastic bucket. While wearing protective gloves, paint the cut surfaces with the herbicide solution using a 1″ paint brush. Apply only enough to cover the surface; do not let any run off the surface. A 10″ paint roller on an extended handle can be used to apply the herbicide to the small stems cut with the string trimmer. Again, be careful not to load the roller with too much herbicide that could drip off. Hold the roller at the cut height and pull it across the cut stems; do not let the roller touch the sand surface. Labels change frequently; refer to the current herbicide label for specific application information. Never exceed the rates recommended on the label of the specific product applied. The label is the law. This herbicide is slow acting, taking three to four months to observe the full affects. The cut plants should be monitored for re-sprouting and if sprouts are noticed, they should be recut to expose a fresh surface and re-painted with the herbicide solution. Beach vitex seedlings should be pulled up as soon as they can be safely identified.
Six months after the herbicide is applied, remove the dead beach vitex plants and sea oats and bitter panicum seedlings should be planted on an 18″ grid as discussed above. Remember that property owners are required to obtain a permit from the Office of Coastal Resource Management before planting on the beach dunes.
What to do if you See New Areas of Beach Vitex?
Beach vitex does become established in areas that are distant from an established planting. It does so by a combination of seed being washed to a new area during storms or by storms breaking off sections of the rapidly growing shoots and depositing these shoots in new areas. Seedlings are easily removed by hand. Larger plants may need to treated with a herbicide as described about or hand removed.
This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.