Playing Cupid for the Double Coconut

World's largest seed: double coconut Lodoica malvidica 
see in Foster Botanical Garden, Honolulu
The fitbit is for scale, but better is the dandelion at the top
of the seed. The seed is way bigger than a whole
dandelion plant.

I saw the double coconut, Lodoicea maldivica (palm family, Arecaceae) seeds, largest in the world--see previous post link--lying on the ground inside their cages at the Foster Botanical Garden in Honolulu in April 2018.

I've seen seedling coconuts (Cocos nucifera); they send up a pretty dramatic set of first leaves.

Young coconut palm, Cocos nucifera, with four leaves
Note the coconut at the base

With the double coconuts, nothing seemed to be happening.


Found only in the Seychelles, remote islands in the Indian Ocean (map), double coconuts have the largest seeds in the world. The big seeds are tasty, look erotic, and are big, so lots of people want one. Over the last century so many seeds were harvested that there was very limited reproduction by these palms. Currently the seeds are protected--like parts of endangered animals, you need permits to possess them--but poaching continues. In the wild they are confined to just two islands and so a disaster--fire, flood--might wipe them out. Consequently people planted them around the world.

Or tried. Double coconuts in the Seycelles simply fall to the ground, germinate, and grow. Elsewhere it hasn't been so easy. First, they are truly tropical palms; they need warmth and water all year round. Second, by the time the big seed is transported across one or more oceans, the embryo inside may have died. There are some growing in tropical places like Singapore, India, and Hawaii but most are young. Double coconuts are so slow-growing that any seed planted today will not flower until 2050.

double coconut Lodoica malvidica
This is the 80 year old pistillate (female) palm in Honolulu

Foster Botanical Garden, Honolulu, Hawaii, part of the Honolulu Botanic Garden system, has a tall double coconut, about 80 years old, which makes it approaching its full size. It has flowered since at least 1984.

But double coconuts are dioecious; each individual plant is either male (makes pollen) or female (develops fruit). The one in Honolulu is female. Without pollen, it (she) will never produce fruit and seeds.

Elsewhere in the world, though, other botanic gardens have male double coconuts.

It was an opportunity for humans to play cupid.

In June 2011, pollen from a male double coconut in Singapore was flown to Hawaii to pollinate their tree. I imagined an intrepid botanist climbing the double coconut in Singapore, a 100-foot palm with flowers more than 50 feet in the air. Then, pollen in hand, climbing down, racing to the airport (because, containing sperm, pollen rarely lives very long) and flying to Honolulu to climb another tall tree and carefully brush the pollen on the stigma of the female flowers (also 50' or more in the air).

Long distance pollination can go like that. But my imagined story was too simple. Singapore and Honolulu tried that in 1984, and 1996, and again in 2000, but by the time the pollen reached Honolulu, even flying on the 15-hour direct flight, the pollen arrived covered with mold. Useless.

In June 2011, when the Honolulu double coconut again flowered, the botanists tried a new technique, dehydrating the pollen. Since double coconuts are trees of the wet tropics, they were afraid that would destroy the pollen, but somehow they had to stop the mold. George Staples and team gathered pollen from the palm in Singapore, dried it at low heat, and packed it into three vials, in a bag lined water-absorbing silica-gel crystals.

In this case, they didn't send it with a person but, rather, entrusted it to a shipping company that promised the pollen would be in Honolulu in 48 hours. In fact, it took more than 120 hours. You can imagine the anxiety of the Honululu team, waiting hour after hour for the pollen that didn't arrive.

R. Silva pollinates double coconut, 2011

Finally the pollen from Singapore was delivered. Two vials of pollen were carefully refrigerated, packed in new dessicant crystals. Fifty feet off the ground, Romel Silva brushed pollen from the third vial onto the flower, even though by this time the stigma of the female flower on the Honolulu palm seemed dry and no longer receptive. But then, one of the ten flowers began developing into a fruit!

Two months later, the Honolulu palm opened another cluster of flowers. Silva climbed the tall palm three more times to hand-pollinate these fresh flowers. Eight double coconut fruits started to develop.

Slowly.

They expected to wait seven years for the fruits to ripen.

R. Silva with nearly ripe fruits of double coconut in Honolulu, 2017

In January 2017, seven fruits, weighing up to 35 pounds, began falling to the ground, ripe. Faster than expected.

The delighted botanists took the huge fruits into the nursery and set them on pans of soil watching for germination. The first seeds germinated in 4 months, much less than the year it takes on the ground in the Seychelles.

Once each seed had produced a good-sized radicle (seedling root), they were planted outside. That was what I saw in April 2018, seeds lying on the ground. The radicle, if it was still alive, was invisible, down under the seed, establishing roots for the plants. Once the root system is established, the seed sends up its first leaf. In April, 2018, the seeds had been lying on the ground for most of a year without putting up a leaf.

After my trip, I watched for announcements that leaves had appeared, but saw nothing in the press.
When I returned to Honolulu in December 2019, I was eager to find out if any had leaves.

And, wow, five of the seven had a leaf.

First leaf, double coconut, Lodoica maldivica
Honolulu Dec. 2019

First leaf, double coconut, Lodoica maldivica
Honolulu Dec. 2019

Not just a leaf, a leaf 4-6' tall and at least 3' across. They will continue to feed off the big seed for a while yet, as the plant grows up and up. Years from now the young plants will develop a trunk and in 25-30 years they should flower. Since there are at least five, it is likely that there will be some males and they won't have to ship pollen from Singapore (though to prevent too much inbreeding, they may want pollen from the Seychelles).

To see a mature double coconut in the United States, you have to go to Honolulu. There are younger plants elsewhere in Hawaii. People plant them in Florida and California but they cannot survive hard frosts, which occur occasionally in all the continental U.S. except Key West, Florida (for example, Miami link), so there are mostly immature plants. Buying a seed of double coconut, if you can find one for sale, will cost more than $500, plus applicable permits.

There is at least one in Europe. In 2003, Stephen Blackmore of the Royal Botanic Garden in Edinburgh, Scotland and his team, took three seeds there and one germinated and survived to be the center piece in their greenhouse. The Royal Botanic Garden website has very nice photos of the stages in germinating a massive, deep rooted, 100' palm in a greenhouse (link). The tale of germinating the seed is imbedded in their paper (cited below, online: link).

There is much more to read about double coconuts: historical stories from when only the seeds were known, beliefs that it is an aphrodisiac, the seed as food, the palm's role in its native forest...lots of things.

This last tale is relevant to pollinating double coconuts:

According to the people of the Seychelles, when the double coconuts in the forest mate, the male walks across to the female and the two palms copulate wildly, huge leaves thrashing in the forest canopy. Any human present is instantly turned into a native gecko or endemic black parrot, never to report what they witnessed.

Dangerous business, reproduction of double coconuts.

Comments and corrections welcome.

Many thanks to Ramel Silva of Honolulu Botanical Gardens for filling in the pollination story for me and sharing his photos.


References
Blackmore, S., S-C. Chin, L.C. Seng, F. Christie, F. Inches, P. W. Utami, N. Watherston and A. H. Wortley. 2012. Observations on the morphology, pollination and cultivation of coco de mer (Lodoicea maldivica (J F Gmel.) Pets., Palmae). Journal of Botany. link Accessed 01/04/20.

Gollner, A. L. 2008.The Fruit Hunters. Scribner, New York. Chapter on The Lady Fruit (double coconut) highly recommended. 
Morgan, E. J., C. N. Kaiser-Bunbury, P. J. Edwards, F. Fleischer-Dogley and C. J. Kettle. 2017. Tracing coco de mer's reproductive history: Pollen and nutrient limitations to fecundity. Ecology and Evolution. 7: 7765-7776.
Staples, G. and W. Singeo. 2017. Dessicating palm pollen. Landscape Hawaii. May/June 10-12.

Kathy Keeler, A Wandering Botanist
More at awanderingbotanist.com
Join me on Facebook: https://www.facebook.com/AWanderingBotanist