The Native Palms of the Ryukyu Islands of Japan

Japan has six native species of palm tree. Four of these are endemic to Japan. There are a further three species, which have been cultivated in Japan for centuries. These are:
Rhapis excelsa (Thunb.) Henry, J. Arnold Arbor. 11: 153 (1930).
Rhapis humilis Blume, Rumphia 2: 54 (1839).
Trachycarpus fortunei var. wagnerianus Becc., Webbia 5: 70 (1921).

Two native species are found only in the Japanese Ogasawara-shoto or Bonin Islands (typical oceanic islands, located 1,000 km south of Tokyo, Japan). These are:
Clinostigma savoryanum (Rehder & E.H.Wilson) H.E.Moore & Fosberg, Gentes Herb. 8: 465 (1956). Endemic.
Livistona boninensis (Becc.) Nakai, J. Jap. Bot. 11: 222 (1935). Endemic.

The remaining four native species are the subject of this article, and these species are found in the Ryukyu archipelago of Japan or Nansei-shoto. These are:
Arenga ryukyuensis A.J.Hend., Taiwania 51: 298 (2006). Endemic.
Livistona chinensis var. subglobosa (Hassk.) Becc., Webbia 5: 16 (1920).
Nypa fruticans Wurmb, Verh. Batav. Genootsch. Kunsten 1: 349 (1779).
Satakentia liukiuensis (Hatus.) H.E.Moore, Principes 13: 5 (1969). Endemic.

The Ryukyu Islands (Figure 1) are a chain of Japanese islands that stretch south-west from Kyushu to Taiwan: the ÅŒsumi, Tokara, Amami, Okinawa, and Sakishima (Miyako and Yaeyama) islands, with Yonaguni the southernmost. The largest of the islands is Okinawa. These islands have a subtropical climate with mild winters and hot summers.

Ryukyu Islands

Arenga ryukyuensis
This palm is very similar to Arenga engleri from Taiwan, but differs in the pinnae being strongly ribbed adaxially, and the stems are only to about 2 m tall, whereas, Arenga engleri stems grow to over 4 m. tall. Arenga ryukyuensis seeds are also very globose, short and fat, whereas, Arenga engleri seeds are more elongate, also generally larger. Arenga engleri in Taiwan occurs at 200 – 1050 m. elevation, whereas, Arenga ryukyuensis is a lowland species, and occurs from sea-level up to about 300 m. Indeed, the more common localities to see A. ryukyuensis is on the coral limestone coastal rocks, often in the spray zone.

Arenga ryukyuensis and Cycas revoluta growing together in Okinawa, Japan.

Arenga ryukyuensis and Cycas revoluta growing together in Okinawa, Japan. © Phil Markey

A. ryukyuensis is usually seen growning together with Cycas revoluta, which is also very common, and can also be seen throughout the Ryukyu Islands growing on coastal rocks and cliffs.

Both the cycads and the palms are more frequent at lower levels, becoming more scarce at elevation, nevertheless, both are found at the highest elevations in Okinawa.

Right: Cycas revoluta Okinawa, Japan. Left: Arenga ryukyuensis and Cycas revoluta growing together in dense undergrowth, Okinawa, Japan.

Right: Cycas revoluta Okinawa, Japan. Left: Arenga ryukyuensis and Cycas revoluta growing together in dense undergrowth, Okinawa, Japan. © Phil Markey

Arenga ryukyuensis showing form, and white undersides of the leaves.

Arenga ryukyuensis showing form, and white undersides of the leaves. © Phil Markey

Another difference between Arenga ryukyuensis and Arenga engleri is the infructescence. A. ryukyuensis fruits are somewhat exposed and visible from above, growing out of the top of the plant. Whereas, A. engleri fruits are often hidden in amongst the leaves, and almost never visible from above. Fruit of A. engleri ripens from green, through an orange/yellow to dark purplish red. A. ryukyuensis ripens from green through yellow to orange then dark red.

Left: Arenga ryukyuensis fruits. Right Arenga engleri fruits.

Left: Arenga ryukyuensis fruits. Right Arenga engleri fruits. © Phil Markey

Taiwan is a new island that started being pushed up from the sea-bed around 6.5 Ma, by the north eastward movement of the Philippine plate crashing into the Chinese continental margin at 8 cm. per. year. This would have crashed through the Ryukyu archipelago / Luzon volcanic arc, pushing any pre-existing islands into the new Taiwan landmass. It is therefore logical to assume that Arenga existed first in the Ryukyu, which are very much older islands, and was then taken to Taiwan to evolve into Arenga engleri. It is not possible that there has been a land-bridge between Taiwan and the Ryukyu since that time.

Livistona chinensis var. subglobosa
I have written before about this species, so will not spend too much time discussing it here. Only to say that Livistona chinensis does not exist in its truly wild state anymore anywhere within the Ryukyu or Taiwan. In Japan, so-called virgin L. chinensis forest is now found only on the islets of Aoshima and Tsukishima in the Miyazaki prefecture, Kyushu, Japan. The islet of the gods on Aoshima is the extreme northern limit of the species, and this is also officially recognised as the largest single population of the species in Japan consisting of 4000 individuals. But as I have published before, this is not acurate, the largest virgin population of Livistona chinensis var. subglobosa is to be found on a tiny island called Uotsurijima (Japanese) or Diaoyudao (Chinese). This is the largest island of the Senkaku Islands (钓鱼岛及其附属岛屿) or what we know as the Pinnacle Islands. Uotsurijima or Diaoyudao Island located at 25°44’39”N 123°28’26”E has an area of 4.3 square kilometres (1.7 sq mi) and a highest elevation of 383 metres (1,260 ft). L. chinensis is the dominant tree species on this island and I estimate this population to be over 100,000 individuals.

Left: An interesting picture of Livistona chinensis var. subglobosa growing through an old house on Okinawa, Japan. Right: Livistona chinensis var. subglobosa in Taiwan tends to grow much straighter trunks.

Left: An interesting picture of Livistona chinensis var. subglobosa growing through an old house on Okinawa, Japan. Right: Livistona chinensis var. subglobosa in Taiwan tends to grow much straighter trunks. © Phil Markey

It is more often than not that the Japanese Livistona trunks are seen to be leaning, bent, twisted, and show irregular growth patterns. I’ve questioned this in Japan, and was told that the Ryukyu islands experience many typhoons, which bend the trees over. But, coastal Taiwan experiences the same typhoons, and the Taiwan trees tend to have much straighter, upright trunks. Another, difference is that many of the Ryukyu trees produce much more globose, almost round, seeds than do the Taiwan trees. The Taiwan Livistona produce more globose seeds than do the Chinese trees.

Nypa fruticans in habitat on Iriomote Jima, Ryukyu, Japan.

Nypa fruticans in habitat on Iriomote Jima, Ryukyu, Japan. © Phil Markey

Nypa fruticans
Nypa fruticans exists in Japan in one single, very isolated, and inaccessible population at Funaura on the island of Iriomote Jima.
This population of about 28 or more clumps are located a long way up a tidal tributary stream in a large mangrove swamp that surrounds a stunningly beautiful tidal estuary on the north of the island.

Tidal estuary and tidal tributary stream leading through the mangrove swamp. Iriomote Jima, Ryukyu, Japan.

Beautiful tidal estuary and tidal tributary stream leading through the mangrove swamp. Iriomote Jima, Ryukyu, Japan. © Phil Markey

The Nypa population is carfully monitored.

The Nypa population is carfully monitored. Some of the overhanging mangrove has been cleared away to see if this has any effect on the population growth. © Phil Markey

I must say that these Nypa palms are not good examples. Much better examples are to be seen, in much more accessible locations elsewhere in South-east Asia. The Japanese Nypa are located deep in an important mangrove, declared as a natural monument in 1959, well off the beaten track. This mangrove is an important habitat for wildlife, and is best left to the wildlife that inhabit it.

Nypa fruticans reproduces by vegetative propagation, each clump connected together under the mud.

Nypa fruticans reproduces by vegetative propagation, each clump connected together under the mud. © Phil Markey

The population is the world’s northernmost natural occurrence, and it has been rapidly reduced in size. Its genetic diversity examined by the Random Amplified Polymorphic DNA(RAPD) method showed that all 28 individuals examined were genetically identical and had no diversity. They are thus considered clones derived from a single individual by vegetative propagation. Because flowers fail to set fertile seeds, the species is likely to be self-incompatible. The population at Funaura is at an extinction crisis.

Nypa fruticans showing self-incompatible emergent flowers. Iriomote Jima, Ryukyu, Japan.

Nypa fruticans showing self-incompatible emergent flowers. Iriomote Jima, Ryukyu, Japan. © Phil Markey

Satakentia liukiuensis

Satakentia liukiuensis © Phil Markey

Satakentia liukiuensis
Satakentia contains only one species, which is endemic to Japan in the far south of the Ryukyu Islands in the islands of Ishigaki Jima and Iriomote Jima. This genus was named by Harold Moore for Toshihiko Satake, who had noticed it was something special. There is now a museum built to honour Toshihiko Satake within the main population of the palms on Ishigaki Jima.

Trunks can be very tall, brownish/grey, and solitary, topped with a prominent, brown or reddish green crownshaft, which is very distinguishable. With large green pinnate leaves, 3 m. long.
The inflorescences are also distictive, which are branched to two orders, and are borne below the crownshaft.

Trunks have a mass of adventitious roots at the base, and can grow to 20 m.tall. © Phil Markey

Trunks have a mass of adventitious roots at the base, and trunks can grow to 20 m.tall. © Phil Markey

Satakentia liukiuensis is in decline in its natural environment with no known cause, and it was once much more widespread throughout the two islands than it is today. However, plants are being raised in cultivation and are widely planted as a street tree in cities further north, notably Naha on Okinawa.

Satakentia liukiuensis in natural habitat. Ishigaki Jima, Ryukyu, Japan. © Phil Markey

Satakentia liukiuensis in natural habitat. Ishigaki Jima, Ryukyu, Japan. © Phil Markey

Satakentia is grouped in the subtribe Carpoxylinae, which comprises three genus – Carpoxylon, Satakentia, and Neoveitchia. Carpoxylon and Neoveitchia come from Vanuatu and Fiji, it is not clear how the natural distribution could extend to the Japanese Ryukyu for Satakentia.

Satakentia liukiuensis in natural habitat. Ishigaki Jima, Ryukyu, Japan. © Phil Markey

Satakentia liukiuensis in natural habitat. Ishigaki Jima, Ryukyu, Japan. © Phil Markey

Satakentia liukiuensis in natural habitat on Iriomote Jima.

Satakentia liukiuensis in natural habitat on Iriomote Jima. © Phil Markey

There are two main wild populations, the main population on Ishigaki Jima, and a much smaller population on Iriomote Jima with a few individual trees scattered across Iriomote. The Iriomote trees are inaccessible, as they grow in a cemetery, or the isolated trees are remote in the hills.

More info:
Satakentia liukiuensis trebrown.com
Nypa fruticans trebrown.com
Arenga ryukyuensis trebrown.com
Livistona chinensis var. subglobosa trebrown.com

Communal Pots for Palm Seedlings

Growing large numbers of palm seedlings economically

This was originally posted on the Trebrown forums in 2006. The thread is now closed. However, you’re welcome to leave a comment on this blog.

"I have large quantities of Phoenix sylvestris, Phoenix loureiri var. humilis, and Phoenix reclinata. I would prefer to avoid planting each seed into individual pots, as this would be very costly and time consuming on my part, so I’d like to grow them directly in the soil. Would it be possible to sow them directly into the soil, or should I try the ‘baggie’ method and then transplant directly into the ground when I see signs of root growth? Would either of those give good results? I’ve already got some Phoenix canariensis in baggies that have sprouted, and I’ve put half of them in pots – the other half are still in the bag as I’m wondering if I shouldn’t just stick the rest in the ground. Any help with this would be appreciated."

Well! I guess the first question should be; Where are you? If you’re in a reasonably warm climate then you stand a good chance of germinating them in the ground. Phoenix generally germinate better when planted in pots rather than by using the poly bag method. They need quite a bit of moisture, which when given to them in the bag tends to rot them faster. They need heat. Around 30°C (90°F) you might get away with about 25°C but germination will be slower and you may have some losses. So if you can maintain these temperatures in the ground then they will germinate. They are not too fussy about soil types. The main problem you’ll have by planting them directly into the ground will be losses through animals eating them.

"Thanks so much for your reply. I live in the US in North Florida – some sources say US zone 9a, others say zone 8b. It’s pretty warm here (averaging mid 70’s to low 80’s F, with evening temperatures in the high 50’s to low 60’s right now). I would assume it’s not warm enough to get them to germinate directly in the ground right now? Perhaps sow them in flats and transplant into the ground when they show signs of growth? My soil is quite sandy and somewhat dry, which would make germination even more difficult I’d think, unless I were to amend the soil where I’d plant. I’m primarily concerned with having to place them all into pots, as with the amount of seeds I’ve got, it would prove to be very costly and time consuming on my part. Jason."

Hi Jason! Yes! You’re better off planting them in pots. But not flats though! Especially the P. silvestris. You’ll find that these will send down radicals to about 12" to 18" from the outset. That will make it very difficult to prise the roots out later. The best way to handle Phoenix on a mass scale is to plant them in very deep communal pots. Get a deep pot and place a piece of fabric over the holes in the bottom. Then fill the pot ¾ full with a coarse sand or grit about 4mm. Then the last quarter fill with compost. Throw the seeds on top. They can completely cover the surface and be piled two seeds high. Then cover with about 1" of compost. Place the pot on a hotbed about 90°F, water well and cover with plastic. Depending on the species, the seeds will germinate on mass in about 1 or 2 months. Water regularly (being such a well drained medium, you’ll need to water daily). After about a year in that pot there will be a mass of roots. But not to worry about that, the roots will easily lift out of the coarse sand with minimal damage. You might want to place a few stones on top of the seeds to hold them down and force the roots through the sand. They have a tendency to push themselves right out of the pots.

"Your technique for starting them sounds really good to me – I will try it that way and definitely report back with how it worked out! You’re sure that it’s a good idea to leave them in the pots like that for a year though? Will they not set out leaves after a couple months? That’d be quite a tangled mess I would think, but at least it gives me some time to figure out if I should then pot them up individually or just plant them in rows in the ground. What say you? Anyhow, thanks a ton for your advice – it’s much appreciated!"

Jason I raise 10s of thousands of Phoenix seedlings every year! There is no other way to do this more effectively. There will be a lot of roots, but if you have a deep enough pot the roots will be mainly straight. I didn’t mean to say ‘lift them out’ in the last thread. I’m just used to saying that. You can’t pull them out. You tip the pot on it’s side and gently pull the plants. The sand will just fall off the roots. The longer (up to about 24 months) you leave them alone the less plants you will loose through transplant shock.

One thing I ought to mention is feeding! For the first year and part of the second the plants take all of their food from the seed. After that time they will require feeding on a regular basis, because the sand holds nothing for them. It is usually better to lift them after the first year. Even young (two year) seedlings would get eaten if you transfer them to the ground. You would be better off potting them on. Despite what some people say about under potting palms, Phoenix like over potting in deep pots, and plenty of water during the growing months.

Communal Pots

I’ve had people ask about the method of growing palms in communal pots. So here is an example of the best way to handle Phoenix palm seedlings on a mass scale – Plant them in very deep communal pots. Get a deep pot and place a piece of fabric over the holes in the bottom. Then fill the pot ¾ full with a coarse sand or grit about 4mm. Then the last quarter fill with compost. Throw the seeds on top. They can completely cover the surface and be piled two seeds high. Then cover with about 1" of compost. Place the pot on a hotbed about 90°F, water well and cover with plastic. Depending on the species, the seeds will germinate on mass in about 1 or 2 months. Water regularly (being such a well drained medium, you’ll need to water daily). After about a year in that pot there will be a mass of roots. But not to worry about that, the roots will easily lift out of the coarse sand with minimal damage. You might want to place a few stones on top of the seeds to hold them down and force the roots through the sand. They have a tendency to push themselves right out of the pots. Adriaan asked:

a) For which species can I use this method of (mass) planting?
b) How deep should the pots be to give the roots plenty of space for growing in a straight line down?

To answer the second question first; Always as deep as possible! This depends on the species, some species produce very long roots from the outset, up to 60cm (2 feet) long. Others produce much shorter roots. You need to know what the species you’re growing requires. But It’s generally better to provide a deeper soil than you need. The answer to the first question is much more general; I grow most species of palm using similar methods, but not all. Some species, and I’ll use Bismarckia nobilis as an example ought to be planted individually in their own deep pots, because deep rooting species like this don’t like having their roots disturbed. But for most other species; they get planted in my nursery in one of two ways; The one I’ve already mentioned, using a lot of sand, and for species with a more tropical requirement, and where they require better water retention in the soil I use only ¼ of sand in the bottom of the pot with the rest of the pot filled with compost. With Phoenix and several other species; The seeds can be sown directly into the pots. But most species of palm require some kind of pre-sprouting method like the ‘baggie’ method with applied heat.

"Thanks for you answer. But, when I use this method, is there no problem with the small leaves? Example; Trachycarpus fortunei will make some wide leaves, is the space for the leaves no problem? And a pot of 60cm deep? That’s almost impossible to handle. Can you give some more specific depths for some species like : Cycas revoluta, Wodyetia bifurcata, Dictosperma album, Trachycarpus fortunei, Phoenix canariensis, Phoenix loureiri var humilis, Phoenix roebelinii, Roystonea regia, Ravenea rivularis, Chamaerops humilis, Archontophoenix alexandrae, Hyophorbe lagenicaulis, Hyophorbe verschaffeltii, Pachipodium lamerei and the Pritchardia thurstoni? I hope you can give 1 or 2 depths which I can use for most species. And I assume that this method wont work with cycas revoluta and wodyetia bifurcata seeds, or do you think that will work also? Thanks Adriaan."

Hi Adriaan. That’s a lot of questions for one thread! The first bit about the leaves; I don’t really understand! Palms being Monocots start life by producing a single strap leaf. They will produce about five strap leafs before they start producing their true leafs. In the first year (depending on species) they will only produce 3 or 4 leafs. The mass planted seedlings look like grass growing in the pot. Yes! Deep pots are always hard to find. But if you’re growing on a really large scale you can use large bins. On a smaller scale, try using specialist palm pots or rose pots. It’s not too expensive to fill these pots because you’re using mainly sand. Wodyetia bifurcata does very well in communal pots. But I grow my Cycads in individual pots. I know some people do grow Cycads in communal pots. I won’t answer your question here for all the different species you mentioned. It would get too long! But one I ought to mention is Ravenea rivularis. I grow these in communal pots with a lot of sand, but these really need a lot of water, so you must remember to keep watering them. For the other species; you need to think of their requirements. Are they deep rooting species (radicle forming)? or are they shallow rooting species? Do they require a very well drained soil or do they require a good water retaining soil? These answers can be found in books about the individual species or you can ask here about a particular species. But I generally give each species a few cm deeper soil then they will use.

"What is best method of mixing your own potting soil for: A) sowing seeds and B) replanting palm seedlings? I live in the Caribbean (hot climate all year. What should I include to make the seedling grow healthy and good? Please include quantities for your suggestions. Hamilton."

Hamilton, I make all my own seed and potting mixes. For many palm types the seed mix should not contain any loam (garden soil) for some it is OK but I don’t for any palm seeds. The best seed mix is simply 50% peat or cocofibre and 50% course sand. That works well for most palms, but I make a 70% peat to 30% sand mix for some of the more tropical and water requiring palms. For potting on it’s more complex, but I try to replicate the natural environment’s soil from the origins of the palm as much as possible. A potting mix should be rich in all trace elements and as deep as possible.

Deep Pots

If you live in the USA there are a couple of manufacturers of very deep pots. Namely, Steuwe and Anderson Die. I have considered importing these into the UK before, however I’m still not sure if the extra cost is justifiable. Deep rooted palms do pose a real problem, because a relatively small plant requires an exceptionally deep pot, and if you were to use an oversized pot for these it over inflates the cost of the plant commercially. Flower buckets make excellent communal pots for sprouting palm seeds on mass. We use plastic fish boxes or other similar boxes commercially for this purpose. But this doesn’t provide an answer for potting individual palms. Although the flower buckets are suitable for some of the larger species. For potting on we have taken to using the black expandable gusset polythene pots that were popular a decade or more ago in the nursery trade. The commercial sizes are not suitable so we have these manufactured to our specifications. I.e. we have the standard commercial sizes but we add 2 to 3 times the height to the pot. The drawback is that expanding palm roots will soon split the bags. But we use that as an advantage and plant the bag with the plant in larger pots as and when needed. This aids the plant by minimising root disturbance during re-potting. These expandable gusset pots also offer a number of other advantages i.e. the much cheaper cost, and you can cram a lot more plants on to a single growing bench allowing minimal run off of liquid fertiliser.

I can only think of one instance where one would plant seeds direct into the poly pots. That is for Jubaea. Those seeds are sprouted first then planted in 1-litre narrow poly pots which are filled only with sand. The sand prevents rotting which so often happens with Jubaea, and of course seedlings don’t require any nutrients in the soil, as they get all that they need from the seed. As soon as the roots start breaking through they are potted on, bag and all in a proper growing medium. I suppose you could do the same with Brahea, Bismarckia, Borassus, Attalea, Butia, Corypha, Hyphaene and many more of the exceptionally deep radicle forming species. We don’t though; we plant all the higher value deep rooting species direct into their own rigid pots from the outset. Butia are communally planted. The gusseted poly bags are used almost exclusively for potting-on until a deep rigid pot is justified.

"When can I move my seedlings outside?

I now have various palm seedlings in pots on windows sills and in propagators around the house from seeds I bought from you. Now that I have bought a greenhouse, would you be able to advise at what time of year I could bring some of these outside into the greenhouse. I have all sorts from individual Euterpe edulis pots to communal pots of 100’s of Washintonia (looks like grass) Also, does a greenhouse speed up the growing process? As you advised in another thread seedlings grow about 4 strap leaves per year and I just wondered what helps this speed up; i.e. direct light from a lamp on the plants when in the house in the winter? Thank you Douglas."

Hi Douglas, It’s the number of Growing Degree Days (GDD) in the year that will make your palms put on the most growth. So obviously you’ll maintain those temperatures better indoors or under glass than you will outdoors. Your glasshouse may not be as warm as your house at this time of year, so you’re better at making the decision when to move them. Your glasshouse will maintain better light and humidity than your house though, and your palms will welcome that. Your potting on from the communal pots is very much different for each species. At most you would only want to leave them communal for 2 years. But the Washingtonia and Euterpe are very fast growers and you should over pot these now, feed them well and stand back and watch them grow, both require a lot of water during the growing months.

"Thanks for your response Phil. Does that mean each individual strap leaf plant needs to go in its own pot or could I just take the rose pot I’ve got 100’s in and pot into an even bigger pot? Thank you Douglas."

Hi Douglas, If the plants are too crowded then they will self thin themselves out until only the one strongest plant remains. They not only need to be potted up individually, but they need to be done with care not to damage the roots, and they’ll need very deep, over sized pots. If you’ve followed my advice from above then you will have planted those Washingtonia communally in very deep pots or boxes. In the bottom half of the pot would have been course sand. Now when you gently lift the seedlings out you will find that the sand falls off the roots, and with a little gentle prying you will be able to separate all the seedlings without damaging any of the roots. When a palm root gets damaged, then that root will die back to the base of the stem, where a new root will grow to replace it. If you damage all the roots (and there are probably only 2 roots per seedling) then the plant has no roots, and will die before it has chance to put out any more. Palm roots are not like other tree roots. You can’t prune them in the hope of making them bush up. This is the same for mature palm trees. If you want to transplant a mature palm you should dig around the tree one year, then return the second year to under cut. This will permit new root growth around the surface of the soil from the first lot of damage, and mean that the tree has a new set of roots to carry it through the transplant. You must find the deepest pots you can find for your Washingtonias. The same is true for all desert palms. These send down long roots through the sand in search of water, and you need to accommodate these roots as best you can. And despite what I’ve heard some people say, Washingtonia will grow very very fast if they’re over potted in large pots, well fed, and given plenty of water during the growing months.