Flowers and leaves. Nearly-ripe fruits. A cultivated hedge of Vitex rotundifolia (Photograph courtesy of Tâi-gí 台語 CC0 1.0 Public domain). A bizarre Vitex rotundifolia topiary in Texas (Photograph courtesy of David Creech ©). A wild, and thus more natural-looking, pōhinahina (Photograph courtesy of Forest & Kim Starr CC BY 2.0).    

Growth Requirements

General 

    Today, pōhinahina is extremely popular with commercial landscapers in Hawai‘i because: (1) it is an attractive plant with its silvery leaves and numerous purple flowers, (2) it is very easily propagated from stem-cuttings, (3) it grows well under cultivation in many unnatural environments such as clay soils and non-coastal areas, (4) it tolerates extreme pruning. In your landscape, you can let your pōhinahina grow in its natural pōhina form or prune it into a manmade shape such as a hedge or even a topiary (see photographs above); the plant will grow well regardless. Pōhinahina is very good for both erosion and weed control. It even looks great as a container plant — maybe, try a hanging basket! For the most silvery leaves and maximum flowering, plant or place your pōhinahina in a site with full sunlight for all or most of the day — it will do poorly in a constantly shaded site — and water it very little or not at all depending on the rainfall at your site. Pōhinahina can tolerate extreme heat, drought, strong winds, and salt spray, and it will grow in just about any type of soil (i.e., sandy, coralline, lava/cinder, clay, organic-dominant).

    In Hawai‘i, wild pōhinahina tend to behave themselves. This is frequently not the case with cultivated plants. The mistake too many people make is watering their pōhinahina too often; automated irrigation systems should be avoided like the plague! When pōhinahina is frequently watered, it becomes aggressive and can quickly take over vast expanses of the landscape, crowding out other plants, while it puts down new roots (from its stem nodes) as it spreads. Later control or removal is a backbreaking nightmare!

    Pōhinahina really doesn't need to be fertilized unless you want to promote more rapid growth, in which case, apply a controlled-release fertilizer with minor elements or foliar feed with an organic or inorganic kelp water-soluble fertilizer diluted to ⅓ to ½ the recommended strength. 

Pests and Diseases

    Pōhinahina is resistant to most pests and diseases, perhaps due to its minty fragrance. However, plants are infrequently attacked by aphids, mealybugs, scale insects, and spittlebugs; these pests are often farmed and protected by ants. During wet periods, powdery mildew and an unidentified leaf-rot fungus may infect pōhinahina. Fortunately, both fungi usually disappear with drier weather. Refer to the Pests & Diseases page for ways to combat the above pests and diseases.  

Special Features and Information

General

    Pōhinahina was recently placed in the very large Mint family (Lamiaceae) containing some 7,000 species! Some well-known, mostly aromatic, members include spearmint, peppermint, lavender, rosemary, basil, sage (Salvia), savory, marjoram, oregano, thyme, shiso or perilla, yerba buena, lion's ear (Leonotis), coleus, chia, lemon balm (Melissa), horehound, pennyroyal, catnip, hyssop, clerodendrum, teak (Tectona), and Mesona, used in making "grass jelly" [WikipediA;Lamiaceae].

    Native Hawaiian members of Lamiaceae include the endemics: honohono (Haplostachys haplostachya), the only non-extinct (of five) Haplostachys species; Stenogyne with 21 species; and the nearly-endemic Phyllostegia with 32 species. Indigenous Lamiaceae species include: pōhinahina, ʻalaʻala wai nui wahine (Coleus australis), and the pitcher sage or pakaha (Lepechinia hastata), which is questionably indigenous.

Hawaiian Name

    Pōhina means “to fall prone” or “topple,” which is indeed the way pōhinahina grows. Additionally, it means "gray" or "misty," which may be a reference to the color of its leaves [Pukui & Elbert 1986]. Pōlinalina is an Oʻahu name for this plant [Wagner et al. 1990].

Etymology

    Vitex is derived from the Latin word, viere, which means "to bind or twist," a reference to the flexible creeping stems of some species [Wagner et al. 1990]. The species name, rotundifolia, originates from two Latin words: rotundus, meaning "round" and folium, meaning "leaf" [Latdict].