Introduction to Cycas, one of the largest genera of CycadsBy Geoff Stein (palmbob)
September 7, 2008
Cycas is one of the largest genera of Cycads and, for me, one of the most mind-numbing as so many look so much alike that I really don't know where to start trying to differentiate them. That may not sound like a hopeful start to an article on such plants, but it just an introduction. But there are many dozens of beautiful landscape and collectable plants in this genus that are quite different and striking. This article will introduce the reader to some of these plants including most of the more commonly grown species (but certainly not ALL the Cycas species- there are dozens of species I have no photos for, and nearly as many I have never heard of- for full coverage you will need to buy a book).
Cycas species in park in Hawaii
Cycas in are in the family Cycadaceae, while just about all the other cycads are in Zamiaceae. There are some huge variations in this species in terms of size- some are quite small with their stems mostly underground, while other species are branched above ground and can grow as tall as 30', closely resembling palm trees.
Cycas 'circinalis' about 20' tall in LA Cycas siamensis in native Thailand large, old Cycas revoluta in LA
The leaves of this species do not vary much from species to species, so with over 90 species currently recognized (and possibly dozens still be to described officially) this makes telling these plants apart a real challenge, particularly for me. Most Cycas have narrow, smooth-edged leaflets which have a prominent midrib, which allows one to at least tell a Cycas species from any other cycad. 4 species have divided leaves though a few other cycads have similar divided leaves (a few Macrozamias). Most have flat leaflets though some have very keeled leaflets. Most have smooth plastic-like bright green leaves, but a few have bluish to grey leaves and some have fuzz (tomentum) on the undersides.
long flat pliable leaves of Cycas 'circinalis' stiffer leaves of Cycas wadei binnate leaves of Cycas micholitzii
Cycas leaves coming up showing how they unfurl, sort of like a fern leaf (Cycas taitungensis, Cycas thoursii and Cycas curranii)
Two examples of Cycas leaves uncurling (Cycas curanii and Cycas tanguinii); Showing typical leaf bases of Cycas leaves and the thorns
The females have no true cones as exist in all other cycad species, but more a semispherical cluster of leaf-like growths that cover the seeds. The males have cones that look a bit more typical for cycads. As will all other cycads, plants are dioecious (male or female, never both). Reproduction normally requires a native insect pollinator, or in cultivation, a human pollinator equipped with a paint brush and access to pollen. But many species within this genus are prolific suckerers and most offsets root easily if proper care is taken (see link below in paragraph on Cycas revoluta)
Cycas pectinata female cone Cycas panzhihuaensis female cone Cycas bifida female with ripening fruits
Cycas panzhihuaensis male Cycas taigungensis male Cycas revoluta male in foreground and female behind
Cycas can be found all over the southern half of the old world, with the major populations in northern Australia and Asia. There are few on Africa and many on the islands in the south Pacific.
Cultivationally there is quite a broad spectrum in this genus with some growing in arid, desert climates, some growing in moist, hot jungles and some from cooler temperate climates that see some frost or even snow. I have grown about a dozen species of Cycas and find them, with a few notable exceptions, to be slow and unpredictable in my climate (southern California), and some simply impossible. But a few are among the most popular of all the cycads grown around the world (notably the Sago ‘Palm'). In most cases the Australian species are easier to grow here (no surprise there), the bluer ones easier to grow in arid climates, the deep green, thin-leaved ones in tropical climates and the temperate ones in just about any climate. This is one of the cycads I find grows better in a pot until it has some size on it (same for most Macrozamias and Zamias), unlike Dioons and Encephalartos that seem to do as well if not better in the ground). This may be because they like their roots moister and/or warmer until large enough to deal with a less hospitable environment. Many species do not like growing in full, hot suns and some tolerate an amazing amount of shade. Cycas species, like most Cycads, are toxic and one must remember this when planting such plants where one will also have pets and livestock. More pets are seen at the emergency room each year for Cycas toxicity than for any other cycad-related problems.
Cycas cairnsiana is a good desert species (Australian); Cycas micronesia is tropical (Marianas Islands near equator); and Cycas revoluta is hardy in just about any situation (from temperate climates in the far east)
Though cycads for the most part are pretty trouble free when it comes to bugs (sort of tough as well as toxic for most garden pests), this genus is exceptionally susceptible to a species of scale that is really tough on it. This scale is a lot more of a problem in tropical climates (like Florida and Hawaii) than in an arid climate like southern California.
leaf of Hawaiian Cycas panzhihuaensis with scale, Cycas circinalis in Thailand with scale, and lastly a large male cone of Cycas chamaoensis in Hawaii with scale
The following is a brief discussion of some of the more common and likely to be encountered species in cultivation. Many are ones I have tried growing myself, but most are not.
Cycas revoluta, or Sago Palm (aka King Sago), is by far the most commonly grown cycad species around the world. This is mostly due to its amazing adaptability and partly to ease or reproduction and ease of growing from offshoots/suckers. This Japanese cycad can be grown in hot, arid climates, hot, humid climates, cool temperate climates, and if given enough light, indoors around the rest of the world. It is called Cycas revoluta because of its 'revolute' leaf edges (recurved). The thin, stiff leaflets are deep green and the leaves are markedly keeled to a 'V' shape (compare to the similar and also commonly cultivated Cycas taitungensis which has nearly flat leaves, but is otherwise nearly identical). This cycad is a moderately fast grower (for a cycad) and if given enough water and heat, can grow from a seedling to a coning adult in less than 10 years. Like most cycads, this species likes to be well fertilized. It can also handle being watered frequently as long as it is warm, in strong light and the soil is very well draining. Growing these in clay and shady conditions can result in rot. This species is frequently bonsaid which is not something many other cycads tolerate that easily. Plants can tolerate cold down to about 20F in a dry, arid, Mediterranean climate, but seems more tolerant of cold (down to 15F) in a normally warm, humid climate (like Florida). Ultimate height is about 15' (can take nearly a century to grow that tall) and it usually produces hundreds of suckers/offshoots from the base of the caudex as well as all along the trunk. For more on how to remove and grow suckers see this page. For more on Sago Palm cultivation, see this page.
Cycas revolutas in cultivation (private garden, and botanical garden) my own seedling showng some sun burn on lower leaves
Bonsai plant on left, and new flush of leaves on right
suckers covering this trunk (photo cactus_lover); bare trunks repeatedly cleaned of these suckers; ripe seed fertilized by insects naturally
Cycas 'circinalis', or Queen Sago, might be the second most commonly grown cycad species but it is for sure the second most commonly used Cycas species for landscaping. The reason I have ' ' around circinalis is because there is still controversy over whether the plant 99% of the world is calling Cycas circinalis is indeed this species, or if it's a form of Cycas rumphii. Some cycad experts says the real Cycas circinalis is actually a much rarer and smaller species... but for the sake of avoiding more confusion I will refer to it here as Cycas 'circinalis'. Cycas 'circinalis' is the more 'classic' looking Cycas species and unfortunately many similar looking species are often identified as this because of it's 'typical' appearance. This is a much taller (up to 20'), more elegant species with longer leaves and flatter, thinner, pliable leaflets. It is hard to say where this species originates as it is found all over tropical Asia. It is a pretty adaptable plant, too, but not nearly as hardy as Cycas revoluta, struggling in hot, dry climates, burning badly in blazing, arid sunshine, and struggling and dying in freezing temperatures down below the mid 20sF. It really does not grow that much faster than Cycas revoluta, at least in terms of visible activity (a good year will see 4-5 leaf flushes in each species), but this species gains far more height per leaf flush.
Cycas 'circinalis' in Florida, private garden in California, and in botanical garden in California
Suckering specimen in private garden, and a larger one in a botanical garden. This species makes a great potted plant, too
large plants in Hawaii, and Borneo
Cycas taigungensis, or Prince Sago, is perhaps the only other very commonly grown Cycas species in cultivation, at least at this time. The reason this species has become recently quite popular is its similar appearance to Cycas revoluta, but more rapid growth rate and greater robust size. This plant is often confused with Cycas revoluta, but has flatter leaves (no deep keel in this species). Otherwise it appears to be nearly as cold tolerant, sun tolerant and as useful as a landscape and potted plant as is Cycas revoluta. Until recently, this plant was incorrectly called Cycas taiwaniana, but in the taxonomy world, it is the first species to be named something that ends up keeping that name. So Cycas taiwaniana is a name that belongs to another plant (unfortunately NOT a native of Taiwan, as this species IS, further adding to the confusion!).
One can see from these photos how similar this species is to Cycas revoluta and how one might confuse the two
Cycas revoluta on left and Cycas taitungensis on right; leaf of Cycas taitungensis showing its flatness; leaf of Cycas revoluta showing the 'V' shape
Nursery mass producing Cycas taitungensis in California; large plant about to cone; Cycas taiwaniana, often confused with Cycas taitungensis, is a completely different species
The rest of the Cycas below will only be discussed briefly as they are far less common in cultivation. A few I know less than nothing about and will not discuss other than showing a photo of them.
Examples of some Australian Cycas species:
I have grown several of these plants and some are very well suited for my hot, arid, inland, southern California climate (but not the clay soils, so I have to do a lot of amending). But for the most part these are slow growing plants and a bit touchy for me. They almost all do better in pots at least until quite large.
Two shots of Cycas angulata and one of Cycas cairnsiana. Cycas angulata is a very large Australian species that can grow up over 25' tall, though I would assume such plants are hundreds of years old. It has the typical thin leaflets of many Australian cycads. Leaves are nice and blue as they shoot up and turn sort of greyish with maturity (though in a humid climate as these two plants are growing in, they remain a lot greener). Cycas cairnsiana is one of the bluest of the Cycas species (sometimes call Cycas 'Mount Surprise') and is a spectacular plant for arid, hot gardens. I have one that is struggling since some plants have grown over its full day sun exposure so will have to move it to a sunnier spot. This is an easy species to rot with overwatering, and it really needs a lot of heat.
One of my personal favorites: Cycas ophiolytica. This is another 'blue' Cycas species from Australia (aka Marlborough Blue) that I find much less finicky than Cycas cairnsiana, and a much faster grower as well. Here is a shot in Thailand, Florida (where it stays fairly green) and my own plant from seed about 10 years old).
Two examples of Cycas media, another large species from Australia (one of the more commonly available, too), and third photo is of Cycas platyphylla
By far the majority of Cycas species are native to Asia. A few of these are relatively common, but most are rare in cultivation, and there may be dozens yet to be discovered and described throughout Asia.
Cycas rumphii, often confused with Cycas circinalis, is one of the more commonly grown species of Asian Cycas (this one also grows in Africa)
another shot of Cycas rumphii, and two shots of Cycas thouarsii, another fairly common species in cultivation (that also looks similar and gets mixed up with these other two a lot)
Cycas curranii is a species I find surprisingly easy and fast in California
Cycas panzhihuaensis is another species that adapts well in southern California climate (see mass production of this plant in second photo)
Cycas wadei is another one I have had luck with (my plant in second photo and has done great in this climate... until I planted it in the ground)
Cycas pectinata (Indian) also does well in California
Cycas guizhouensis does OK in Cal, but these are in Florida and Hawaii, where the humidity and constant heat are much easier on most Cycas species
Cycas bougainvilleana Cycas campestris Cycas chamaoensis
Cycas changjiangensis Cycas clivicola (photo by WebInt) Cycas dolichophylla
Cycas apoa (known for its wavy leaflets) Cycas edentata Cycas falcata
Cycas ferruguinea Cycas hainanensis (this one's in Southern California!) Cycas hongheensis
Cycas pachypoda Cycas tanguinii (a beauty!) Cycas tansacha (another good one for California)
Last, but not least, are the bi and multipinnate Cycas species that are often collectors items because they are so different looking. I have grown some of these in California (as have many others) and some are surprisingly hardy here and do better than many of the other tropical species for some reason. These plants tend to have underground caudeces and consist only of a few tall leaves shooting out of the ground and an ornamental array of unusual leaflets (for a Cycas, at least). All these are Asian plants.
Cycas micholitzii is by far the most common of these unsual-leaved Cycas species and does well if given some protection from cold. But as you can see, it does not hold a lot of leaves at one time.
Cycas bifida has enormous leaves (over 15')
Cycas debaoensis is one of the best of these split-leaf species (mine is doing well so far); Cycas multipinnata is another great looking plant but also does not hold a lot of leaves at one time
So there certainly is some variety within this genus as you can tell, but I have left out a large majority of them in this article (mostly as I had no pictures to go with them) and of those left out, I would hard pressed to tell 90% of them apart. But these are great plants for landscaping, particularly if you live in the tropics or humid temperate climates and can get you hands on them (most of these are exceedingly rare plants in cultivation and can be very pricey).
For more about Cycas species, or cycads in general, visit the Cycad Pages: http://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/