The most common and in most cases, invasive/noxious, introduced taxa include ironwood (Casuarina equisetifolia), golden crown-beard (Verbesina enceloides), wild poinsettia (Euphorbia cyanospora), haole koa (Leucaena leucocephala), sweet alyssum (Lobularia maritima), buffalo grass (Stenotaphrum secundatum), peppergrass (Lepidium virginicum), and Bermuda grass (Cynodon dactylon). Fifteen of the native taxa are indigenous, or found elsewhere beyond the Hawaiian Islands, and nine are endemic to the Hawaiian Islands. None of the endemic taxa are restricted to Midway Atoll (Wagner et al. 1990).
Shrubs usually grow clumped close to the ground, but can grow up to 3 m tall.
Common name: Tree heliotrope
Introduced and naturalized. Small tree up to 5 m or more in height. Leaves simple, alternate and appearing whorled at branch tips. Blade fleshy, 10-20 cm long, densely silky pubescent (covered with soft hair) on both surfaces. Flowers sessile (lacking stalk) in stiff, widely branching. Calyx deeply divided about halfway into 5 elliptical lobes. Fruits white to green, globose, 3-6 mm long, ultimately dividing into four nutlets. Native to tropical Asia, Madagascar, tropical Australia, Tuamotus, and most of the low and high islands of Micronesia and Polynesia. A modern introduction to Hawai'i. Tournefortia has become naturalized and relatively common in coastal areas on Kure, Midway, and Pearl and Hermes Atolls; Lisianski and Laysan Islands; French Frigate Shoals; and all of the main Hawaiian islands, except Kaho'olawe.
It grows in littoral forest on rocky and sandy coasts, and is particularly common in sandy open habitats of atolls, often being the tree species closest to the ocean. On Midway and other Northwestern Hawaiian Islands, Tournefornia serves as nesting habitat for our shrub-nesting seabirds. On Midway, this plant flowers and seeds from May through November.
Since the tree is small, it is not very good for timber, but the wood is sometimes used for making gongs, canoe bailers, tool handles and carved handicrafts, and parts of the tree are reported to be used in native medicines in the Society Islands and Tokelau. The leaves were once used in the preparation of a red dye in Tahiti.
Trailing glabrous vine with purple stems, often rooting at the nodes, fleshy to nearly woody from a thickened taproot, up to 5 m or more long.
Indigenous. Slender annuals. In favorable conditions, these plants can become short-lived perennials. They are tufted with fibrous roots or short rhizomes (horizontally creeping underground stem which bears roots and leaves). Culms are stiffly erect, 20-50 cm tall, trigonous, smooth. Leaves are few, subrigid, linear, and much shorter than the culms. Inflorescences (flower head) open, forming a simple or partially compound umbelliform corymb (dome or dish-shaped inflorescence) with 2-7 rays, contracted into a head-like cluster 2-5 cm in diameter. Spikelets are yellowish brown to pale or dark reddish brown, numerous, and crowded. Achenes (seeds) are dark brown, oblong-obovate, laterally flattened, about 1 mm long.
Native to tropical and subtropical regions worldwide. In Hawai'i, common on open or grassy, often disturbed areas, from mesic coastal sites to mesic and wet forest. Found on Midway Atoll and all of the main Hawaiian islands except Kaho'olawe. On Midway, this plant can be found in disturbed and wet areas. Plants are growing, and seeding from March through November.
Common name: Bunch grass
Indigenous. Perennial. Culms densely tufted, tough, stiff, strictly erect, up to 2 dm tall, sharply scabrous (rough-surfaced; bearing short stiff hairs), almost completely covered by leaf sheaths. Blades up to 5 cm long, but usually shorter, upper surface has short, stiff hairs or bristles. Inflorescences paniculate, weakly branched, sharply scabrous; spikelets few to ca. 40, straight to somewhat curved, 5-45 mm long, flattened, 1-2 mm wide. Caryopsis golden brown, somewhat flattened, subglobose to ovoid, 0.5-0.8 mm long, 0.4-0.5 mm wide.
Native to the Pacific equatorial region; in Hawai'i occurring in coastal sites on coral sand, gravel and saline flats, sometimes as a pioneer species. On Kure, Midway (Eastern and Spit islands), and Pearl and Hermes atolls, French Frigate Shoals, and formerly at Barber's Point, O‘ahu. On Midway, plants observed with inflorescences from May through November.
Native Plants on Midway Atoll NWR