Euphorbia degeneri
formerly Chamaesyce degeneri
Euphorbiaceae or Spurge family
Synonyms: Anisophyllum cordatum, Chamaesyce cordatum, Chamaesyce degeneri, Chamaesyce degeneri f. minuscula, Chamaesyce degeneri var. molokaiensis, Euphorbia cordata, Euphorbia degeneri f. minuscula, Euphorbia degeneri var. molokaiensis
ʻAkoko
ʻEkoko, Koko, Kōkōmālei
Beach sandmat, Spurge
Natural Range & Environment
Euphorbia degeneri is endemic to all the main Hawaiian Islands except Kaho‘olawe [Flora of the Hawaiian Islands]. It is found scattered in coastal areas (but see next paragraph) from sea level to 50 m (164 ft) [Wagner et al. 1990].
Joel Lau, an expert botanist known for his rare finds and analysis, has discovered an ‘akoko on the basaltic cliffs of windward O‘ahu (Ko‘olau Mountains) that matches the description of Euphorbia degeneri. You can view his photographs of these plants at this Flickr link.
Like many other ‘akoko, Euphorbia degeneri produces small specialized inflorescences that have tiny reduced (i.e., no petals or sepals) male and female flowers that sit atop a cup-like base called a cyathium. Each cyathium has one central female flower (with a branched stigma) surrounded by one to several male flowers. If pollinated, the female flower's ovary enlarges to form a fruit capsule that hangs to the side of the cyathium (Closeup photograph courtesy of G.D. Carr ©.). Here, held between black gloves, are several inflorescences at different stages of development. My (Koebele) best guess is that the yellow cyathium in the photograph's center is the base of an old inflorescence with either an exploded or unpollinated female flower at its center (Photograph courtesy of Forest & Kim Starr CC BY 3.0 US.). ʻAkoko leaves can vary in color from green to blood-red (Green ʻakoko photograph courtesy of Forest & Kim Starr CC BY 3.0 US; red and green ʻakoko photograph courtesy of Mike Wood CC BY-NC 4.0.). A cultivated ʻakoko quite "happy" in its non-coastal habitat.
Description
Euphorbia degeneri is a small (often less than 12 inches (30 cm) across) prostrate subshrub with a lifespan exceeding five years. It has numerously-jointed stems with thin gray to brown bark/skin and a milky sap that may irritate those with sensitive skin; avoid getting the sap in your eyes. The round to elliptical leaves are green to blood-red, hairless (or nearly so), and arranged in pairs opposite each other along the stem. During periods of severe drought, plants will drop many of their leaves. Damaged green leaves turn red, orange, or yellow.
Euphorbia degeneri produces small specialized inflorescences that have tiny reduced (i.e., no petals or sepals) male and female flowers that sit atop a cup-like base called a cyathium. Each cyathium has one central female flower (with a branched stigma) surrounded by one to several male flowers. Occasionally, an inflorescence will develop without a central female flower. Wild plants seem to produce their small inflorescences most of the year except during periods of extreme drought. Cultivated plants bloom sporadically or continuously.
The ovary of a pollinated female flower develops into a green capsule that hangs to the side of the cyathium on a stalk as it grows larger. When ripe, the capsule rises up from its downward-curved position and becomes upright shortly before exploding to disperse the few tiny white seeds inside. Currently, my (Koebele) best guess is that old cyathia with an exploded (or unpollinated) female flower turn yellow.
Growth Requirements
General
While it's possible to grow this little ʻakoko inland as an accent in a native Hawaiian coastal or rock garden, it will face fewer threats if you keep it as a container plant. Euphorbia degeneri grows too sparsely to be used as an effective weed-controlling groundcover.
Fill your container with crushed coral (mostly at the bottom) and sand. Alternatively, you can fill the container with black cinders. Place the container with your ʻakoko in a site that receives full sunlight for all or most of the day.
Water your ʻakoko minimally; around once or twice a week is more than enough for this xeric plant. Do not overwater.
Euphorbia degeneri grows at a moderate pace, and you should have a plant 6 to 12 inches (15 to 30 cm) wide in about a year. Fortunately, this little ʻakoko begins flowering early, perhaps as soon as three months in its container. If your plant seems to stop growing or never flowers, you can try using a foliar organic or inorganic fertilizer at ⅓ or ¼ the recommended strength. And, if you are interested in collecting the tiny seeds to grow more plants, look for and harvest any ripe capsules in the morning. Ripe capsules will straighten from their downward-curved position and become upright shortly before they explode to disperse the tiny seeds inside.
If your ʻakoko begins to overflow the container, it's okay to hand-prune some of its branches. However, do this slowly, a few branches every couple of weeks, and take care not to get covered with the milky sap exuding from the cuts; Euphorbia sap can cause skin irritation. You can also try growing new plants from the cuttings; however, this is more difficult than growing them from seeds.
I (Koebele) haven't yet figured out why some ʻakoko have all green leaves while others have a mixture of red and green. It's true that if you damage a leaf (try squeezing one really hard), it will turn from green to red. However, I have often seen wild and cultivated ʻakoko with red leaves and no signs of leaf damage. Perhaps it's just genetics, like in the case of color variations in some other plants (e.g., ʻākulikuli (Sesuvium portulacastrum)), or it's a mix of genetics and environmental conditions; an interesting project for a graduate student wanting to work on native Hawaiian plants. If you're interested in learning more, here's an online article by Nathan Taylor to get you started: Euphorbia leaf colors and patterns.
Pests and Diseases
ʻAkoko is occasionally attacked by mealybugs, scale insects, spider mites, and whiteflies. However, this is rare, and, in the case of mature plants, the pests often disappear over time, probably due to natural predators such as ladybird beetles or leaf shedding. ʻAkoko's milky sap may also deter many pests. Refer to the Pests & Diseases page for ways to deal with each of these pests. Persistent infestations are more likely if you have placed your ‘akoko in an unnatural environment, such as a heavily-shaded or windless site; consider moving your plant to a sunnier and windier location rather than resorting to continued chemical treatments.
Another ʻakoko pest is the giant African snail (Lissachatina fulica), which will come out of its hiding place at night and girdle the stems or eat the leaves of ‘akoko; girdled stems eventually die. If this happens, first try to solve the problem by moving your ʻakoko to a safer location. Also, closely inspect your container to make sure the snail(s) are not living inside. Refer to the Pests & Diseases page for other ways to deal with snails.
Uses
Ancient Hawaiian
There are about 17 endemic species of ‘akoko found in Hawai‘i, depending on which taxonomist you talk to. All possess a milky sap. According to Krauss [1993], the sap was used in the paint for canoe hulls. Under E. lorifolia, Hillebrand & Hillebrand [1888], page 396, state, "The tree is much used as firewood." Pukui & Elbert [1986] state that Euphorbia (Chamaesyce) multiformis leaves and buds were chewed to treat debility. This claim likely originates from Ka‘aiakamanu & Akina [1922], who recommended this practice for mothers and babies.
Note: The milky sap of all Euphorbia species can cause skin irritation, warts, and, despite the claims above, should not be ingested without medical supervision due to potential toxicity.
Modern
Special Features and Information
General
Euphorbiaceae is a large family with about 7,500 species within 300 genera, found on all the continents except Antarctica, with the greatest diversity in the tropics. Some well-known non-native relatives of ʻakoko are the Castor oil plant (Ricinus communis), kukui (Aleurites moluccana), poinsettia (Euphorbia pulcherrima), cassava (Manihot esculenta), and the Pará rubber tree (Hevea brasiliensis) from which we get latex [WikipediA;Euphorbiaceae].
There are currently (2026) 17 native species of Euphorbia in Hawai‘i — all endemic to the Islands. Several species are either vulnerable, rare, or endangered, and two varieties are considered to be extinct [Flora of the Hawaiian Islands]. They range in stature from very prostrate shrubs like Euphorbia degeneri to tall trees like Euphorbia haeleeleana and Euphorbia olowaluana [Wagner et al. 1990].
While not all the native Hawaiian Euphorbia species have been thoroughly investigated, a study by Pearcy & Troughton [1975] of 12 species (including E. degeneri) found that they all appear to utilize C4 photosynthesis, an adaptation that enables greater water-use efficiency and improved growth in hot, dry environments when compared to the more common C3 photosynthesis seen in most plants. While most C4 plants are grasses or herbs, the native Hawaiian Euphorbia are among the few examples of woody plants — specifically trees like E. olowaluana — that possess the C4 photosynthetic pathway, which usually involves a specialized anatomy (i.e., Kranz) that can be challenging for tree growth.
In addition to the many endemic Euphorbia species, the only other member of Euphorbiaceae native to Hawai‘i is the endemic poʻolā (Claoxylon sandwicense) [Flora of the Hawaiian Islands].
Hawaiian Name
ʻAkoko comes from the Hawaiian word for blood, koko. This is likely a reference to the red, or blood-colored, seed capsules that look like drops of blood on many Hawaiian Euphorbia species [Krauss 1993, Neal 1965]. Alternatively, some believe the name comes from the observation that ‘akoko leaves, when damaged, often turn red, giving the appearance that the plant bleeds when it is injured.
Etymology
Euphorbia is named after Euphorbos, a Greek physician of King Juba II of Numidia and Mauretania (52–50 BC – 23 AD), who married the daughter of Anthony and Cleopatra [WikipediA; Euphorbia], and used the sap of a spurge for medicinal purposes [Gledhill 2008].
The former genus name, Chamaesyce, is derived from the ancient Greek words, χαμαί (khamaí), meaning “near the ground,” and συκῆ (sukê), meaning "fig-tree," perhaps referring to the low habit of most species and the fig-like appearance of the fruit capsules [Wiktionary;Chamaesyce].
The species name, degeneri, honors noted botanist(s) Otto Degener (1899–1988) and Isa Degener (–Hansen) (1924–2018), husband & wife, both botanists and conservationists who specialized in identifying the plants of Hawai‘i. Among the many books and papers they co-authored, the most influential was Flora Hawaiiensis, which appeared in seven volumes between 1932 and 1957 [WikipediA;Otto Degener].
BPK