Native Hawaiian Garden (7722)

Euphorbia haeleeleana – What was that?

Prior to John (Culliney) and I writing A Native Hawaiian Garden, we often went on hikes together to explore the native forests of O‘ahu and the Big Island. One such hike was to a small dry forest remnant above Ke‘awa ‘ula. It was a hot summer day and we had encountered some amazing plants such as a small grove of ‘ahakea (Bobea sandwicensis) and the endangered nehe (Wollastonia tenuifolia). We decided to sit down for lunch atop a cliff face overlooking a deep gulch next to a very small-leafed maile lau lihi. In the distance, we could just see the ocean as the tradewinds provided a refreshing breeze. In the middle of our lunch and conversation, we were interrupted by a strange noise. “What was that?” I asked John. “I don’t know,” he replied. We both sat silently for one minute, two minutes, three minutes, waiting to hear the noise. Nothing. We began talking again and several minutes had passed when we heard the noise again. It sounded like some type of explosion but from a far distance. We finally concluded it must be the sound of a hunter’s rifle several miles away. But then we hear the noise again and this time it seemed nearer and to be coming from the sky above us. Again, we sat quietly looking all around us and listening intensely. After one or two minutes, we hear the explosion again.

It was definitely coming from above us and it wasn’t far away; the sound was similar to that of a single corn kernel popping in the microwave. We then took full notice of the nearby tree perched on the edge of the cliff and instantly solved the puzzle. The tree was a female Euphorbia haeleeleana loaded with ripe fruits, and the mysterious noise was the sound of individual fruits dispersing their seeds as they exploded in the hot midday sun. We both laughed and finished our lunch.

Habitat & Appearance: For a very long time, this plant was only found in one place, the dry and mesic forests of Hā‘ele‘ele in western Kaua‘i, hence the name haeleeleana. However, in 1985, it was discovered in the O‘ahu location described above. (There’s a bit of a dispute about who saw it here first.) The tree resembles plumeria in size and general appearance. The branches are thick but bendable; the leaves are slightly smaller and more rounded than plumeria. Some individuals have a prominent red stripe down the center of each leaf. In the wild, in dry forests, female plants lose all their leaves during the dry, hot summer. On the other hand, most male plants will retain at least some of their leaves all year long.

Euphorbia with fruits (Photograph courtesy of J.K. Obata via G.D. Carr ©). Euphorbia seedlings. Adult Euphorbia with leaves. Header photograph courtesy of David Eickhoff CC BY-NC-SA 2.0.

Euphorbia in Hawaiian Culture: Given the very limited habitat of this plant, it's not surprising that it has escaped recorded Hawaiian reference. With friends and volunteers, I often refer to E. haeleeleana as the ‘akoko tree. Like other ‘akoko, it’s possible Hawaiians utilized the white sap for medicine.

Collecting Seeds: Female trees produce large (3/4 to 1 inch diameter), ripe, yellow-brown, woody fruits in late summer and early fall. Do not collect still-green fruits because they will not contain viable seeds. At home, dry the fruits for several days in a paper bag. Some of the fruits will explode and release their seeds. For the others, crack them open with pliers to get at the seeds. Seeds remain viable in the refrigerator for about a year but then begin to lose viability.

Growing from Seed: Sterilize (with 10% bleach for 15 minutes) and then soak the seeds for 1-2 days in a shallow pan of tapwater. Using Method One, the seeds will begin to sprout in 1-2 weeks and continue for another couple of weeks. Because of the seedlings' rapid initial growth, I transplant new seedlings to individual pots just prior or with the development of their first true leaf. (Rather than using Method One, you might try Method Two, but only with very clean media and surroundings.) I move the seedlings into the nursery (50% sunlight) 1-2 weeks after transplanting them to individual pots. They grow quickly in the light along with a bit of fertilizer. Avoid overwatering because this will cause the seedling to rot and die. After 3-6 months in the nursery, the plants should be 8-10 inches tall and you can safely plant them out into the garden.

Growing from Cuttings: I have not grown this plant from cuttings.

Growth in the Garden: I have only planted Euphorbia out in sunny, naturally watered areas (i.e., I do not irrigate) where most of the rain falls during the winter months. During the wet season, the plants grow rapidly, adding 1-3 feet to their height each year. During the dry summer months, they lose all or most of their leaves and go dormant. My guess is that if you lightly watered your Euphorbia during the dry season, it would grow more rapidly. Naturally-watered Euphorbia mature and begin flowering after 4-10 years (6-10 feet tall). Of course, you will need at least one female and one male plant for viable seed production.

Diseases & Pests: Euphorbia are attacked by scale insects as seedlings in the nursery and as more mature plants in the garden. Stems, leaves, and roots are all vulnerable. You can often remove all or most of the scale insects on the stems and leaves by hand. Below ground, you will need to use an insecticide (see Enemies in the Garden). I have also had a few plants die from rot at their base but am not certain of the cause.

Ā ā Ē ē Ī ī Ō ō Ū ū