Kaena Point ‘Akoko (Euphorbia celastroides var. kaenana) – Propagation hacks

    I am a big fan of YouTube videos on gardening hacks — easy and innovative ways to propagate or care for common plants such as planting tomato slices to grow new tomatoes, or using an ice cream cone as a biodegradable seed-starter pot. Likewise, for decades now, I have tried to discover new and better techniques to propagate native Hawaiian plants. To my credit and great delight, I’ve discovered a few such as embryo extraction for lonomea and olopua, and using gibberellic acid to hasten seed germination of some Scaevola species. Prolonged soaking of ‘akoko seeds — featured on this webpage — is another hack I am proud of. 

    On a related note, it’s interesting how often a particular propagation hack works on more than one species within a particular genus or even family. Perhaps the best known example of this is how scarification often hastens the germination of plants in Fabaceae or the Pea family. Here, the reason scarification works is well knownthe scar permits water to bypass an impermeable seedcoat and reach the embryo. Less understood is why gibberellic acid kickstarts germination in the seeds of some species and not in others. 

    There’s still a lot we can discover about propagation methods for native Hawaiian plants and why they work. This is why I encourage you to take an experimental, rather than cookbook, approach whenever you are propagating any native plant. And, certainly, if you discover a “hack,” please share it — a YouTube video or website is a good and easy place to share.

Habitat & Appearance: Euphorbia celastroides is the most morphologically variable and widespread of all the Hawaiian Euphorbia. This variety, var. kaenana, has a very limited range, being restricted to the dry western tip of O‘ahu. While most common in coastal areas like Ka‘ena Point, it can also be found in open dry montane sites such as the ridges bordering Mākua Valley. The variety is federally listed as endangered. 

     When mature, the Ka‘ena Point ‘akoko is a shrub 1-5 foot in height and 3-6 feet in diameter. The numerously-jointed trunk and stems are composed of a light wood with a gray to brown epidermis. Its sap is milky white, and may irritate those with sensitive skin. Leaves are silvery gray to green, hairless (or nearly so), and arranged in rows along its stems. During drought, the plant will drop most or all of its leaves. Clusters of small flowers develop on side branches with each flower developing into a seed capsule that turns red when ripe and then explodes to disperse 1-4 tiny brown to gray seeds.  

(Top to Bottom) Ripe ‘akoko fruits (capsules) and flowers. Germinating ‘akoko seeds in a drop of water. ‘Akoko seedling. A 17-year-old mature ‘akoko at Leeward Community College.

‘Akoko in Hawaiian Culture: There are about 17 endemic species of ‘akoko found in Hawai‘i (depending on which taxonomist you talk to). All (to the best of my knowledge) share two traits recognized by Hawaiians. The first is the plant’s milky sap that Hawaiians of the past incorporated into a medicine given to new mothers who were having difficulty producing enough breast milk. Krauss (1993) also reports that the sap was used in paint for canoe hulls. The second trait is that damaged ‘akoko leaves often turn red thus giving the appearance that the plant bleeds when it is injured; koko means blood. Alternatively, some believe the name ‘akoko is derived from the red blood-like color of the fruits seen on some species. Pukui & Elbert (1986) state that Euphorbia (Chamaesyce) multiformis leaves and buds were chewed to treat debility.   

Collecting Seeds: In the wild, flowers and fruits can be seen on the Ka‘ena Point ‘akoko for much of the year. However, flowering and fruiting seems to be most intense in the late summer and fall. In cultivation, sporadic flowering and fruiting is common throughout the year. Unlike the ripe capsules (i.e., fruits) of the ‘Ewa Plains ‘akoko, the ripe capsules of Ka‘ena Point ‘akoko do not reveal themselves by become erect and vertical on their stalk just prior to exploding. Rather, they are always vertical on their short stalk, and the only clues to their ripening are their size and color. Ripe (and near-mature) fruits are full size and red (see photograph to right). Collect these ripe capsules and place them in a container to dry. The container (I use an empty cottage cheese tub) should be covered to prevent any seeds from escaping when the capsules explode, but not air-tight which would prevent drying. As they dry, the near-ripe capsules will explode and release their seeds. After several days, you should have one or more tiny seeds per ripe capsule in the container. Place these temporarily in a dish of water to see if they sink or float; the seeds that sink are viable, the seeds that float are inviable and can be discarded. (These are tiny seeds, so stir the water or push the seeds underwater with your finger to break the water's surface tension which can buoy up viable seeds.) Remove the seeds and air dry them for storage. To date, I have not stored seeds of this species. However, I suspect they are similar to ‘Ewa Plains ‘akoko seeds in that they are short-lived at room temperature – perhaps, no more than a year, but can be stored for many years in the refrigerator with little loss in viability.

Growing from Seed: It’s sometimes funny how you discover new things. In this case, I discovered an excellent way to germinate ‘akoko seed simply because I procrastinated. Several years ago, I was soaking some ‘Ewa Plains ‘akoko seeds in a shallow pan of water overnight in preparation for sowing them the next day. Well, I got lazy and left the seeds in the water for an extra day. To my surprise, after only 36 hours in the water, a few of the seeds began to germinate. With a pair of forceps, I carefully transferred each of the germinating seeds to its own small pot filled with clean media; transfer the seed to a dibble tube if you anticipate keeping them in the nursery for over six months. After refreshing the water, a day later, more of the soaking seeds had germinated. After about ten days, replacing the water each day, only a few ‘akoko seeds remained. These, I finally discarded after waiting another week. I have now discovered this prolonged soaking technique works for at least three species of ‘akoko: ‘Ewa Plains ‘akoko, Ka‘ena Point ‘akoko, and a third rare species, Euphorbia kuwaleana. Now, obviously, you don’t have to germinate ‘akoko seeds in the manner I’ve just described – they germinate just fine if you sow them after soaking them a day. However, using this method will eliminate the need to transfer each seedling from a germination flat/container to a larger pot. And, it’s just fun watching the new root emerge from the submerged seeds. 

    ‘Akoko seedlings are tiny, so they take a while to grow large enough to plant in your garden. After sprouting, place the seedlings in full to partial sun to prevent spindly growth and hasten their development. Also be vigilant of animals like snails, slugs, mice, and rats that can quickly eat the seedlings while they are small. After developing six or more leaves, I start fertilizing my seedlings with half-strength liquid fertilize (e.g., Miracle-Gro®) to get them through this vulnerable time even faster. With luck, you should have a plant ten or so inches in height and ready for your garden in 3-6 months.

Growing from Cuttings: I have had very limited success rooting ‘akoko cuttings. In my best attempt using Method Two, only one of five cuttings rooted after about three months. Others horticulturists I know have had much better luck with this species, so, you can try your luck. I suspect (but don't have any experimental evidence) this varied success with rooting may be because of the many different varieties of these species; some varieties may root easily whereas rooting var. kanana is difficult (at least for me). 

Growth in the Garden: This is one of my favorite plants because of how little care it requires. Once your seedling is ten or more inches tall, plant it out in the sunniest and driest spot in your garden, or consider making it a container plant. When planting, give it a really good watering, and repeat this watering once a week for 1-2 months; after two months you should see some significant growth. After that, reduce or stop watering your ‘akoko unless you see signs of drought stress such as dropping its leaves or wilted stems. In fact, continued frequent watering is likely to cause disease or pest problems — remember where this plant naturally grows, Ka‘ena, a very hot and dry place.

Diseases & Pests: ‘Akoko seedlings and adults are occasionally attacked by sap-sucking pests such as scale insects and mealybugs. However, in my experience this is rare, and in the case of mature plants the pests have disappeared over time, probably due to natural predators such as ladybird beetles or leaf shedding. The milky sap also likely deters many pests. Other native Hawaiian plants enthusiasts have reported problems with red spider mite infestations. Persistent infestations are more likely if you have placed your ‘akoko in an unnatural environment such as a heavily-shaded or over-watered site; consider moving your plant to a sunnier and drier location rather than resorting to continued chemical treatments. If you do decide to use pesticides, refer to Enemies in the Garden for the specific pest

    Another pest I just recently had to deal with were African snails which come out of their hiding places at night and girdled the main stem of my newly-planted ‘akoko just above the ground; girdled, the young plant roots eventually starve to death and the plant dies. What I did to prevent this was wrap the main stem in several layers of crinkled aluminum foil from the ground upward about ten inches. This protected the vulnerable stem, and the snails seem to be unwilling to climb up the aluminum foil to get at the bark of the upper branches. Using snail bait/poison might also work, but I thought this non-chemical solution the better choice.  

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