A sunny spot in a lower elevation garden is the perfect place to plant the indigenous Hawaiian plant pohinahina. Also known as beach vitex, this ground covering plant fills an area quickly, even when the soil is poor and irrigation is sparse. Pohinahina is salt and wind tolerant and can also live at upper elevations or in partial shade. This vitex qualifies as a xeriscape plant that can be a trouble-free addition to any garden.
The scientific name Vitex rotundifolia defines the plant’s ropelike stems and derives from the Latin word viere meaning to bind or twist. Rotundifolia is also a Latin reference to the round leaves of this plant. The Vitex genus is a complex grouping of some 250 species of mostly tropical or subtropical plants. The genus was originally classified in the Verbenaceae family, but as recently as 1992, botanists felt the vitex genus should be moved to the Lamiaceae or Mint family. Many other aromatic herbs share this family. Today you may find it classified in either family depending on the date of the source.
Pohinahina grows over a wide latitude range. It is native to seashores throughout the Pacific and can be found as far west as India. It has a north-south range from Korea to Australia. Beach vitex was recently imported to the eastern United States where it has become a seashore invasive. Control efforts are underway to protect the native species and the fragile beach dune ecosystem in the Carolinas, where it is known as “Beach Kudzu.” In Hawaii, though, it is a welcome addition to shorelines and other hot, dry locales.
When choosing plants for the landscape along Ane Keohokalole Highway, native Hawaiian plants including ilima papa, pohinahina and naupaka were selected and planted. Today, the pohinahina and naupaka have overtaken the others and it remains to be seen if those two can coexist or one of them will prove the fittest to survive there.
Pohinahina serves well as a ground cover but could also be referred to as a sprawling shrub since it can grow over 3 feet tall in ideal locations. Though usually less than 18 inches tall, it puts out runners from the mother plant that can grow to 10 feet or more, establishing roots at nodes along the stem. New stems are green and fleshy and become brown and woody as they mature.
The leaves of beach vitex are strongly aromatic, reminiscent of rosemary or other aromatic herbs we associate with Mediterranean gardens. It is delightful to plant pohinahina along pathways in a garden so you brush the leaves as you pass, releasing their aroma. As with many drought-tolerant plants, pohinahina’s leaves have a silvery green color that reflects light. Though the tops of the leaves are a darker green, the entire leaf is covered with tiny hairs. This characteristic is called tomentose in plant lingo.
Pohinahina produces small, 1 inch, purple flowers periodically that form clusters which sit in a pocket of leaves at the stem tips. The blossoms develop into small round green fruit which turn yellow, red and finally mature to a blue-black color. Inside this fruit, called a drupe, you may find as many as four seed compartments. These seeds are usually viable and can be used to grow new plants.
To plant pohinahina seeds you must first remove the outer coating which may require abrading against a wire screen. Use them soon after removal from the plant for best results. Soaking overnight in warm water can also help with germination. Though some of the seeds may float, they are still viable.
Sow seeds in a medium that drains well. Three parts perlite to one part potting mix works well. Cover them with about ¼ inch of soil and water them three times a week until they germinate. Germination may take a month or more. Seedlings grow slowly and should only be watered when the top of the soil is dry. Once you see four true leaves you can transplant to a soil mix that drains well. Within a few months, the plants will start to grow more rapidly and can be planted out in a sunny spot.
Propagating pohinahina from cuttings also works. Choose semi-hardwood stems 4- to 6-inches long with several nodes. Dip the bottom of the stem into a rooting powder and place in a mix of three parts perlite to one part vermiculite. Roots should form on the cuttings within two to four months and the new plants will be ready to plant out in about six months.
Pohinahina is a drought-tolerant plant once established. Choosing a location for your new plant that has good soil drainage is essential. Be sure to allow room for the plant to spread as once in the ground it will send out long stems into the surrounding area. It will grow over rocks, do well in sandy soil and can fill a large area with its overlapping stems.
The aromatic leaves do not attract many pests. Spittle bugs can be washed off easily. Sucking insects such as aphids or scale may get established, especially if “farming” ants are present. An oil and soap solution can usually control these pests.
Pohinahina needs little care. If you fertilize, reduce the concentration to one half of the recommended rate. If the plant becomes too sprawling, it can tolerate severe pruning to manage size and shape and encourage compactness.
Beach vitex has limited medical properties. The leaves were historically eaten to relieve headaches and the juice from the leaves was added to bath water. Today the stems, leaves and flowers are often used to add body and aroma to head lei.
Beach vitex is widely available at area nurseries. Amy B.H. Greenwell Ethnobotanical Garden in Captain Cook usually carries the plant in several sizes.
Overall, pohinahina is a great Hawaiian plant. It attracts bees, can serve as a potted specimen, is an excellent ground cover or hedge and can help control erosion on slopes.
This information has been reviewed for accuracy by Peter Van Dyke, manager of Amy B.H. Greenwell Ethnobotanical Garden.
Diana Duff is an organic farmer, plant adviser and consultant.