Goodeniaceae, the Goodenia Family
This is a variable, evergreen, multi-stemmed shrub that forms rounded mounds that are usually 3 to 8 feet high, but can occasionally attain heights up to 16 feet. The alternate, spirally arranged leaves are densely clustered at the branch tips, and the lower stems bear closely spaced, crescent-shaped scars where the leaves have been shed. Measuring 3 to 9 inches long, the leaves are obovate with a narrow base, giving them a spoon-like shape. The leaves are glossy, lime green in color, with a leathery, flexible texture. They are often revolute (with the margins rolled under), and the leaf apex is sometimes slightly wavy or scalloped.
There are two varieties of this species in Florida. Scaevola taccada var. sericea has leaves that are covered with soft, silky appressed hairs, while the less common Scaevola taccada var. taccada has leaves that are glabrous (hairless) on both sides.
The flowers are borne in groups of three in short, axillary, cymose inflorescences. The corolla is split along one side, giving the flowers a distinctive fan-like appearance, hence the common name half-flower. Each flower has five petal lobes that are pale green outside and white inside, with faint dark lines running lengthwise, becoming pale purple to tan as the flower ages. The flowers are followed by single-seeded, fleshy fruits (known as drupes) with the sepals persisting at the distal end. The drupes are globose to ovoid, about ½ inch long and turn from green to white or yellowish-white as they mature. The small seeds are white to off-white in color, with longitudinally ridged, corky tissue that makes both the seeds and fruit buoyant.
Beach naupaka is native to coastal areas and islands of the Old World tropics and subtropics, including East Africa, Asia, the South Pacific and northern Australia. It is naturalized in Florida, the West Indies and possibly in other parts of Tropical America.
This species is found in frost-free areas along the coast from Brevard and Pinellas counties southward. It is most often observed on coastal strands, but is also found in tidal swamps, beach dunes, rock barrens, maritime hammocks and disturbed coastal sites.
Beach naupaka is most likely to be confused with the threatened native inkberry, Scaevola plumieri. The two are easily distinguished by the color of the mature fruit: black in the native inkberry and white in the invasive beach naupaka. Other characters for separating these two species are summarized below.
Scaevola taccada | Scaevola plumieri |
|---|---|
| Plants to 16 feet high | Plants rarely exceeding 5 feet high |
| Leaves leathery, flexible, 3 to 9 inches long, with margins often revolute | Leaves stiff, succulent, typically 2 to 3 inches long, with margins not revolute |
| Cymes with all flowers pedicellate (stalked) | Cymes with central flower sessile and lateral flowers pedicellate |
| Calyx lobes 3.5 to 5 mm long | Calyx lobes to 1 mm long |
| Fruit white or yellowish-white at maturity | Fruit black at maturity |
It is thought that beach naupaka was initially introduced to Florida from Hawaii through cultivation. In the mid-20th century, it was promoted as a salt-tolerant landscape plant and used for beach stabilization projects. Although it can no longer be propagated or sold in Florida, older cultivated plantings persist and may escape from cultivation. The fruit are consumed by birds and raccoons, which disperse the seeds. The fruit and seeds are buoyant, and the seeds may remain viable for up to a year as they float on ocean currents. Germination is promoted by contact with freshwater, after the seeds have washed ashore. Branches that contact the ground may develop adventitious roots, allowing for vegetative dispersal as well.
The nomenclature of this species has been the source of considerable debate. Other names that have been applied to this species include Scaevola sericea Vahl, Scaevola koenigii Vahl and Scaevola frutescens K. Krause. In Asia, the pith of the stems is used to make rice paper, and all parts of the plant are used in traditional medicine. The leaves and fruit are said to be edible, but not palatable. In Florida, beach naupaka is displacing endangered native plant species. It grows rapidly and produces abundant seed, which has hastened its spread.