Achyranthes humilis has at least two forms, a short inflorescence form and a long inflorescence form (closeup photograph of long inflorescences courtesy of J.K. Obata via G.D. Carr ©). Note the thinner lower "immature" leaves and wider upper "mature" leaves of the plant surrounded by weedcloth. The beginnings of a topiary (photograph courtesy of Greg Koob ©). Header photograph courtesy of Joel Lau ©.

Growth Requirements

General

    Achyranthes humilis is an attractive, easy-to-care-for shrub that should be more common in Hawai‘i landscapes. We suspect its endangered status, and thus its regulated commercial status, may be the reason for its rarity. Use kuluʻī as an accent plant, lightly-pruned hedge, or screen. It also does well in a container (see photograph above).

    Kuluʻī does best in a site with full sunlight for all or most of the day, but is also tolerant of shade; shaded plants tend to be taller and more open-branched than full-sun plants. Once established, kuluʻī grows best with infrequent heavy waterings followed by long dry periods that permit the surface soil to dry out. It is tolerant of extreme heat and drought and can grow in lava/cinder, clay, and organic-dominant soils, provided there is good drainage. We have not tried to grow kuluʻī in sand or coralline soil. Because kuluʻī are often propagated by cuttings (they root easily), they lack a deep taproot and can be toppled and uprooted by strong winds. Therefore, refer to Hibiscus arnottianus: Growth Requirements for how to prevent or deal with this potential problem.  

    In-the-ground Achyranthes humilis initially grow quite rapidly and can be two feet (61 cm) or more tall in a year or less. They also begin flowering about this time. (Plants grown from seed usually take an extra year to attain this size and begin flowering.) After this, growth typically slows down. While normally not necessary for in-the-ground plants, containerized kuluʻī benefit from biannual applications of a balanced controlled-release fertilizer or foliar feedings in the early morning (to avoid burning) with an organic or inorganic fertilizer at ¼ – ⅓ the recommended strength every other month.

    Kuluʻī can withstand pruning provided it is done by hand, and this is a good way to prevent your plant from toppling over in a windstorm. In fact, some native Hawaiian plant enthusiasts have even tried using kuluʻī as a topiary (see photograph above). If you do prune, be aware that kuluʻī cuttings are very easy to root — and, an easy way to give away this rare shrub to friends. Giving away seeds, cuttings, or progeny of your endangered plants is perfectly legal; however, selling them requires an approved permit from the State. 

Pests and Diseases

    Kuluʻī is infrequently infested by sap-sucking insects like aphids, mealybugs, or scale insects. Look for these infestations near the stem-tips. In windless sites, spider mites sometimes attack the leaves. Refer to the Pests & Diseases page for ways to eliminate or control these pests. 

Special Features and Information

General

    The Amaranth family (Amaranthaceae) is a large family with approximately 2,040 species within about 165 genera, most being herbs or shrubs with a few trees and vines. They are found in tropical to cool-temperate regions, with a few, like spinach (Spinacia oleracea) and beet (Beta vulgaris), being economically important vegetables. While the majority of species in the family use the more common C3 photosynthesis pathway, around 800 species are C4 plants [WikipediA; Amaranthaceae]. 

    In addition to Achyranthes humilis, other native Hawaiian plants in the Amaranth family (Amaranthaceae) include five other endemic species of Achyranthes (one of which is extinct); a possibly now-extinct amaranth (Amaranthus brownii) endemic to Nīhoa; an endangered amaranth last seen in 2014 (Amaranthus pakai); five endemic species of pāpala (Charpentiera spp.); and the endemic ʻāweoweo (Chenopodium oahuense) [Flora of the Hawaiian Islands].

    Achyranthes humilis is one of three Hawaiian endemic species with the Hawaiian name Kuluʻī. All three species were previously placed in the endemic Hawaiian genus Nototrichium. However, based on a molecular genetic study by Mccauley & Havran [2013], all three species were recently transferred to the more widespread genus Achyranthes. The other two kuluʻī are: 

• Achyranthes divaricata — a rare shrub endemic to Kaua‘i, found in diverse lowland and montane mesic forests.

• Achyranthes sandwicensis — a shrub to small tree endemic to all the main Hawaiian Islands, found in open dry forests, on exposed ridges, and in lava fields.

Hawaiian Name

    The name Kuluʻī is shared among the three currently recognized species, Achyranthes divaricata, A. humulis, and A. sandwicensis [Wagner et al. 1990], and is sometimes found in the literature without an ‘okina or kahakō [Ulukau].

Etymology

    Achyranthes comes from the Greek words, achyron, meaning "chaff," and anthos, meaning "flower," referring to the chaff-like parts of the flower [Wagner et al. 1990]. The former genus name, Nototrichium, comes from the Latin word, nota, meaning "remarkable," and the Greek word, tricho, meaning "hair," probably referring to the dense pubescence of these plants [Wagner et al. 1990]. However, Achyranthes humilis (syn: Nototrichium humile) does not have the characteristic dense silvery hairs on its leaves like its two sister species (A. divaricata, A. sandwicensis). 

    The species name, humilis, translates as "low-growing" or "close to the ground" [Gledhill 2008], which may be a reference to the decumbent growth behavior of some forms of this species.