Pili flowers. Notice in the photo of barbs with attached seeds (right), as well as seeds with no barbs attached (on right). Clos-eup of leaves and seeds, and planting en masse on a college campus.

Growth Requirements

General

    Pili does well in containers of almost any size, but will quickly outgrow smaller ones. For container plants, small applications of foliar feeding with an organic or soluble commercial fertilizer monthly or every other month, from one-third to one-fourth of the recommended strength, is beneficial. 

    However, pili does better and will grow to its full extent when planted in the ground, where it does not require much care once established. The soil must be well-drained with sand, cinder or organic matter. Pili will tolerate limited partial sun but does best in full sun with good air movement. It can tolerate wet or dry conditions, but overall looks better when given water regularly. It is drought, wind, heat, and salt spray tolerant.

    If pili is planted close together, it forms a tall groundcover or dense low hedge. While it does not need to be trimmed, this can be done once a year or every other year, down to six inches to encourage new growth and maintain a clean appearance by removing the tangled masses of seeds and harpoons. Interestingly, when rain or water drops hit the tangled mass, they start to twist and writhe. Keiki (children) love animated things, even animated plants like Sleeping grass (Mimosa pudica) and Venus Fly Traps. You can carefully gather a bunch of pili seeds/harpoons and show your keiki what happens when water drops on lands on it. The seeds/harpoons will twist and curl, seemingly coming alive, just as the vernacular name Twisted beardgrass suggests! (See Etymology).

    It is important to use native grasses such as pili in the landscape because they are being displaced by alien grasses and shrubs in wild places. Additionally, grasses and sedges add another shape or form to the landscape, fufilling our natural desire to see more than just broad-leaved plants. 

Pests and Diseases

    Pili is occasionally subject to attacks by scale insects, mealybugs, and grasshoppers, but is otherwise generally pest-free. Refer to the Pests & Diseases page for treatments.  

Special Features and Information

General

    Heteropogon contortus, a member of the Grass family (Poaceae), is part of a diverse group of plants that includes approximately 12,000 species and 780 genera worldwide. In the Hawaiian Islands, there are over 80 species of native grasses, many of which are endemic, and some are considered rare and endangered [Flora of the Hawaiian Islands].

    Pili is believed to be indigenous to the Hawaiian Islands. The seeds of pili have harpoon-like attachments that allow them to attach to fur and feathers for dispersal.

    Botanist Joel Lau has identified two forms of pili in Hawaiʻi—an erect type and a prostrate type. The erect type of H. contortus can be found on all the main Hawaiian Islands, while the prostrate type is limited to areas where the trade winds are particularly strong, such as specific sites in northwestern Molokaʻi, northwestern Lānaʻi, and Kalae (South Point) on Hawai`i Island.

    Pili serves as an important habitat for various native creatures, including land snails, and its presence in the Hawaiian Islands contributes to the biodiversity and ecological balance of the region. Small terrestrial snails, including Cookeconcha undescribed sp.?, Lyropupa perlonga, and Endodonta undescribed sp.?, were previously abundant among pili at Koko Head, Oʻahu. They are now only known from sub-fossil/fossil sediments at Barbers Point (Kalaeloa), Oʻahu. It is believed that these snails may have also inhabited habitats similar to the bunchgrass (Eragrostis sp.) found on Nīhoa [Christensen & Kirch 1986].

Hawaiian Name

    Pili means "to cling or stick" [Hawaiian Dictionaries].

Etymology

    The generic name Heteropogon is derived from the Greek heteros, different, and pogon, beard, in reference to the two kinds of spikelets found in the inflorescence of this species. Literally, "varying-beard," (the twisting awns of the female spikelets) [Gledhill 2008]. True to the Latin specific epithet contortus, pili seeds have an unusual habit of contorting when wet to burrow into the soil [Gledhill 2008].