Introduction to Caudiciform Plants, Also Known as Fat PlantsBy Geoff Stein (palmbob)
May 9, 2013
(Editors' note: This article was originally published on February 9, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)
What is a caudiciform?
This is any plant that forms a caudex, or a fat, succulent base/trunk/root. They are also referred to as 'Fat Plants, or Fat-bottomed Plants'. Those with thick, fat stems/trunks with few branches are called 'Pachycauls'. This swollen root or stem is used for water or food storage, allowing the plant long periods of survival without water or other forms of nutrition. Missing from the plant files is this description, which is too bad. Not all caudiciforms fit easily into the category of cactus and succulents, but most do. However, there are caudiciform trees (like Baobab trees), caudiciform vines (like morning glory relatives, members of the grape family, some passion vines) and members of the cucumber family, periwinkles, pelagoniums, milkweeds, yam family, and of course, cactus, Euphorbia, cycads and other succulents. There are over 100 genera of plants that have species that can at least loosely be described as caudiciforms.
Caudiciform plants can be divided up into 4 general forms: Phanerophytes are those plants that have an above-ground caudex and a growing center substantially (25cm or more) raised above the soil level, like this Dioon califanoi on the left (and most cycads), the Adenium swazicum (and all Adeniums, most Adenias, Beaucarneas, Cyphostemmas, and Pachypodiums etc.)
Chamaephytes are those plants with above-ground caudices but in which the growing centers are significantly closer to the ground (like this Euphorbia susannae on the left, and Dioscoreas)
Hemicryptophytes are caudiciform plants with a below-ground caudex, but the growing center is above ground (like this Ceratozamia zergozae on the left) The Boophane disticha on the right is actually a bulb, but is often grouped together with these other 'fat plants'. These plants are cultivated to show off their caudex by raising it up- looks more interesting that way
Geophytes are plants that have both the caudex and the growing center underground, like this Ibervillea on the left and the Trochomeria on the right (as are most caudiciforms in the Cucumber family)
Why grow Caudiciforms?
These are sometimes plants one needs to develop a taste for as not all are attractive or even all that interesting looking, at least not until you get to know them better. They really are fascinating and curious plants. And some are exceptionally attractive specimens. Most growers of caudiciforms grow them in pots in carefully controlled greenhouses, and stage them appropriately to show them off. However some are easy to grow and good for beginning collectors. Still others like to grow them outdoors in warmer, drier climates as part of their landscaping. Growing and collecting caudiciforms can quickly go beyond hobby to obsession, a common occurrence in the plant collecting world. Though most require little actual work, they still take up a lot of time in their care, as some of these plants require precision in their maintenance. Just a little off in heat or water, and one may end up with a large, expensive pile of rotten plant tissue. Large old specimens can be something to be proud of and worthy of showing off. Most cactus and succulent shows have a large contingent of caudiciforms in them.
Though they may not excite the average passerby, these two plants are outstanding examples of their species and fascinating plants for those who like this sort of thing. On the left is an Albuca circinata, a geophytic plant that is really a bulb, but some still consider a 'Fat Plant', with curling grass-like foliage. Avonias can be tough to keep from rotting (on the right) and this is particularly large and happy looking specimen (this is another example of a Chamaephyte)
How does one take care of a Caudiciform?
There is no simple answer to this question. Since there are many examples of caudiciforms in many different and completely unrelated plant families saying anything in general terms about them is difficult. But if one knows nothing about a caudiciform plant and is forced to take care of one, it is probably best to water when it is growing (which is not always when it’s warm out)- ie, has leaves forming. And best to stop watering (at least decrease substantially) during times of seasonal leaf loss. However, some caudiciforms are evergreens, and some don’t appear to be obviously growing, ever. In general, it is best to err on the side of less water than more if you are unsure. Almost all do best in very well draining soil (some have to be so well draining that the soils are nearly pure rock, sand or pumice, or else the plants will rot). And most prefer warmth over cold (again, not always true), so most growers of fat plants have a greenhouse or some protective environment for these plants. The good thing is most plants are somewhat adaptable and one can often keep very unrelated and totally different plants in the same greenhouse or enclosure, despite their varying needs for heat, humidity, light, water and food.
The Aloe dichotoma on the left is a very easy plant to take care of and quite forgiving. But these Raphionacmes, in the right photo, are quite prone to rot if one is not careful
What are some examples of caudiciforms?
There are way too many to include in this introductory article to even hope at some sort of complete list… in fact we won’t even be able to show an example from every genus or even every family that has a caudiciform in it. But the following are some of the more commonly grown caudiciforms in cultivation.
Adansonias, or Baobab trees, are one of the largest of all the pachycaul trees
potted Adansonia in cactus show on left showing the attractive pachycaul swollen trunk, and a large Baobab tree in Hawaii on the right
Adenium obesum (and all other Adeniums) are very popular caudiciforms. Called Desert Roses, these members of the family Apocynaceae are one of the easier caudiciforms to aquire- even finding them at Home Depot or Target is not unusual. However they are somewhat cold sensitive and very prone to rot if allowed to get cold in winter when they are dormant (in cold climate- dormancy is not mandatory and if kept in a nice warm, bright greenhouse these plants will usually continue to grow year round).
3 examples of Adenium obesum growing in cultivation.
If grown outdoors in a tropical climate, Adenium obesum is much less obviously a caudiciform. In fact, a better term might be Pachycaul shrub
Adenium arabicums, very similar species to Adenium obesum, also make excellent potted caudiciforms
Adenias are often confused with Adeniums for obvious reasons (looks and very similar name) but are in a completely different family: Passifloraceae (same family as Passion fruits/vines). First two photos are of Adenia glauca, probably the most hardy of the genus (some can grow it outdoors in southern California), and the weird, spiny plant is Adenia ballyi
Some Aloes are considered caudiciforms, like the large, thick-stemmed South African tree species (eg. Aloe dichotoma and Aloe pillansii). However there are several small caudiciform Aloes, too, such as Aloe richardsiae. The larger aloes are fairly straightforward to grow- all one needs is heat, lots of sun, well draining soil and protection from the cold. Water less in winter, if potted, though these plants do tend to tolerate winter rains outdoors in California.
Aloe dichotoma growing outdoors in southern California showing off its pachycaul trunk
This interesting little aloe is Aloe richardsiae, one of the few aloes that develops a true caudex
Beaucarneas are very well known and commonly grown caudiciforms (were in the Lily family, but now in another family that includes a number of seemingly unrelated plants). These are often known collectively as bottle palms, ponytail palms or Elephant Foot trees. There are generally very easy to grow, some doing well indoors and in humid, rainy climates. These are full sun plants, if outdoors, and quite tolerant of abuses that would kill or rot other caudiciforms.
Beaucarnea gracilis on left and Beaucarnea stricta caudex on right
This is the most commonly kept Beaucarnea in cultivation, Beaucarnea recurvata
Bowiea volubilis, or Climbing Onion, is another very popular fat plant (a bulb, not a true caudiciform), that is more a curiosity than a beauty. This plant, despite its 'tender' appearances, does well as a landscape plant in southern California... but still more a curiosity than a true adornment of the garden. Most growers keep these in pots
Close up of outdoor potted plant, and a greenhouse raised plant
Burseras are Mexican trees that are well known for their peeling trunks and natural tendency to ‘bonsai’. These trees make excellent potted plants and perfect for smaller, multi-species pots as well as fascinating specimen plants. They have fat, often gnarled, twisted trunks with small leaves and need very little water, even in summer. Pachycormis are related Mexican trees with a similar appearance and pachycaul trunks
Bursera microphylla bonsai plant, and what one looks like growing in the ground, Huntington Gardens, southern California, as well as another in a private garden
A Pachycormus discolor being grown as a bonsai tree on the left, showing a great peeling pachycaul stem. On the right is a plant grown outdoors in southern California
Calibanus hookeri is a peculiar relative of the Beaucarneas that is basically a nearly spherical, fissured, lump of stem with grass growing out the top. This is one species that doesn’t seem to have a particular period of dormancy. Just water less in winter and a bit more in summer.
Calibanus hookeri in pot (in wild, the caudex would be mostly underground)
Cycas revoluta and most other cycads, for that matter, are excellent examples of ‘typical’ caudiciforms with their thick, woody caudeces topped with perennial leaves. Cycas revoluta is a very hardy plant tolerating amazing amounts of abuse in terms of over and underwatering, low light, intense heat etc. However, most other cycads are not nearly as tolerant of these sorts of abuses, and one need to be a bit more careful with excess watering, low light and extreme cold… cycads in general are not inexpensive plants so one should do a lot of research when thinking of acquiring one.
Large Cycas revoluta outdoors in California. This species makes a good potted plant as well a landscape plant.
Ceratozamia zergozae showing a lot of caudex (normallly this caudex is underground in this species, one of the Hemicryptophytes), and Dioon sp. 'Queretero', showing a typical Dioon caudex (normally above ground as shown here)
Encephalartos, to some, are THE collector's caudiciforms, and there are over 50 species. Some large plants can go for $10,000 or more, and some very rare species 2-4x that. In these photos are a hybrid Encephalartos longifolius on the left, with an excellent rounded caudex, Encephalartos latifrons, a very rare, old plant, and on the right, a young Encephalartos lehmanii
Macrozamia frazieri, miquelli and a lot of large mooreis awaiting planting- these cycads are some of the larger Australian species
This is an example of a smaller, but still wonderfully caudiciform species of Macrozamia, Macrozamia stenomera. This is an example of another hemicryptophytic cycad
Zamia furfuracea is one of the most commonly grown caudiciform cycads after the Sago Palm, and makes a good 'bonsai' plant as well as landscape species
Zamia encephalartoides is a very rare but highly ornamental species
Cyphostemmas are members of the grape family (they look nothing like grapes except in the color and shape of their fruits). Though most Cyphostemmas are very rare, Cyphostemma juttae is fairly common in cultivation and a simple plant to grow. Eventually these plants develop into enormous caudeces weighing hundreds of pounds and some can grow into small trees. However, most are grown in pots and considered some of the premiere caudiciform species for entering in cactus and succulent shows.
All the above photos are examples of Cyphostemma juttae, the most common species in cultivation, some in full leaf (summer) and some in no leaf (winter)... and a few coming into leaf (spring)
Cyphostemma uter and currori, a true giants of the species, and make not only a great potted plants and frequent show winners, but an amazing landscape plants, too
Though not that common, these Cyphostemmas elephantopus plants are bizzare and highly sought after caudiciforms, despite the less than interesting foliage (this is a hemicryptophytic species with this caudex normally underground, and vining leaves above).
Dioscoreas are in the Yam family, but the ones grown for curiosity and entered in cactus and succulent shows are not the edible versions of yams. These weird, fissured woody plants are caudiciform vines. Most are from Africa, but at least one Mexican plant is popularly grown in cultivation. These are plants best to not water much at all in winters (D elephantipes is an exception), and water moderately in summers. Most are grown as potted plants as they tolerate only so much frost before rotting.
On the left is a small collection (the author's) of Dioscoreas- Dioscorea macrostachys aka mexicana, Dioscorea elephantipes, and the small one in front is Dioscorea hemicrypta (all Dioscoreas are hemicryptophytes, though). The other two photos above are of Dioscorea elephantipes outdoors in the Huntington Gardens, turning orange in fall, and a close up of the wonderful woody scales
Dorstenias are in the fig family (Moraceae) and popular caudiciforms. In general they have green, tapering trunks with huge, weird flowers. These plants are quite cold sensitive, originating from some of the hottest climates in Africa/Asia.
By far the most impressive Dorstenia is Dorstenia gigas, another common show winner. These plants are really pachcaul trees in their native island of Soccotra, but potted they are incredibly ornamental green-trunked beauties. These can be difficult and expensive plants, though
Dracaena draco, and a few other Dracaenas fit the definition of caudiciform plants. The Dragon Tree, Dracaena draco, is a very popular and commonly grown potted and landscape plant, and fortunately very easy to grow. Though it does not have much cold hardiness, it is hardy enough to grow in many climates in southern California and many other mediterranean and desert climates throughout the world. This is a good plant to start with, but it does get quite large eventually.
A potted specimen is one of the easiest and most attractive caudiciforms for outdoor potting (does not do well indoors). On the right is a large colony of trees in Lotusland, California.
The genus Euphorbia is very well represented in the caudiciform group with many dozens of species considered caudiciforms. Some of these are very hardy, easy plants while others are very touchy, east-to-rot plants. Some are almost nothing but caudex while others have only the hint of a caudex and a large, medusoid head of ‘branches’. One of the easiest to grow is Euphorbia stellata, which is amazingly cold hardy, tolerates a lot of water, even in winter, and handles low light as well as intense sunlight quite well. This is a good one to start with. Euphorbia flanaganii is another one that is nearly ‘bullet-proof’ in terms of tolerating all sorts of abuse.
Euphorbia bupleurifolia Euphorbia cauducifolia
Euphorbia guillauminiana Euphorbia unispina
These Euphorbias are examples of plants with caudiciform stems that normally form above ground just as you see them.
Euphorbia decepta Euphorbia flanaganii Euphorbia gorgonis, barely showing some caudex
These three Euphorbias are examples of medusoid plants that also are caudiciform chamaephytes- have short, thick, succulent stems that are both above and below ground normally.
Euphorbia gymnocalycioides and Euphorbia horrida are two examples of many many Euphorbias in which the entire plant is an above-ground caudex
old flowering Euphorbia obesas Euphorbia obesa x vallida
Euphorbia obesas are one of the most popular and commonly grown Euphorbia caudiciforms and are themselves caudices.
Euphorbia buruana (left), Euphorbia primulifolia (right)
Euphorbia stellatas Euphoria trichadenia
These Euphorbias are plants whose caudex is really a root planted above ground in cultivation for effect. In nature these roots would normally be comletely buried in the soil (hemicryptophytes).
Some Ficus species can be grown in such a way that they form caudices. Many have thick, twisted interesting roots, but only a few of the most succulent root/stem species are recognized as caudiciform plants. Ficus petiolaris is one of the most commonly grown as a caudiciform tolerating being grown in very shallow pots with very little water. These plants then form thick, swollen caudices topped with a small head of leaves. However, if grown in deep, rich soils, these tend to turn into ordinary looking trees.
Three photos of Ficus petiolaris, two as caudiciform potted plants, and the last as a landscape plant
Fockeas are another commonly grown genus of caudiciform plants in the milkweed family ( along with Hoyas and a variety of succulents that produce smelly flowers). Fockea edulis, the most commonly grown plant in the genus is a good starter caudiciform as it is fairly easy to take care of and a bit more resistant to rot than the others. Eventually if forms a massive, pale, warty caudex with some vine-like branches that often have to be trimmed back.
All above photos are of Fockea edulis in cultivation. This is one of the more commonly grown and shown caudiciform plants
Fouquierias are Mexican plants, some of which form amazing caudexes, up to 20’ tall or more (e.g. Fouquieria columnaris or Boojum Tree). These are popular show plants and nearly without fail, at least one of these wins best of show (usually a Fouquieria purpusii or fasciculata). These plants form thick tapering green and grey fissured columns adorned with thin, spiny branches and are perfect plants for culture in shallow pots.
These three photos are of Fouquieria fasciculata, probably the most popular of the genus in terms of showing, but a very expensive and slow plant
Fouquieria purpusii is another popular show plant and another slow grower, but a bit less costly. Fouquieria columnaris is not nearly as ornamental a plant, but what a specimen tree!
Some Jatrophas have amazing caudices and are relatively popular plants in cultivation. Jatropha podagrica is probably the one most often recognized as being a caudiciform. In southern California and Florida some are able to grow this outdoors, but in most climates this is a pot plant- and a fairly easy and attractive one to start with.
Jatropha podagrica is a very common plant and 'typical' caudiciform. Jatropha berlandieri is a bit tougher plant to keep from rotting
Operculicaryas are fascinating natural bonsai trees that have pachycaul stems and thick, twisted roots that are often raised up in pot cultivation for looks. Operculicarya decaryi is the more common species and is a pretty easy plant to start with, having some cold tolerance and pretty good tolerance to variable water availabililty.
On the left is a nice show specimen showing the nice twisted, caudiciform roots that have been raised up for show purposes. The larger plant is an exceptional specimen grown as a landscape plant in southern California
Ornithogalums are bulbs, but some put in the 'fat plant' group, and of these plants by far the most popular is the pregnant onion (Ornithogalum longibracteatum), a very easy to grow plant, in both pots and the garden. In fact, this is considered by some an invasive species- makes tons of little babies on its’ spherical, soft, onion-like caudex (the bulb itself), and they just fall off and grow into a new plant wherever they land.
This is the author's plant after a squirrel decided to toss the plant onto the ground, showing the caudex, and the roots. Very hard to kill plant, though
Pachypodiums are very popular caudiciforms and some of the very best and attractive of all the fat plants. Almost all the species are true caudiciform phanerophytes (above-ground caudiciforms), though some are much less so than others. Pachypodium succulentum and bispinosum actually have caudiciform roots that, in nature are underground, but in cultivation are always raised up above ground. Some Pachypodiums get huge (lamerii, geayi and rutenbergianum) while others stay quite small (P brevicaule). These plants are closely related to Plumerias (same noxious white sap), but much more drought tolerant. Some are easy to grow, while others are really for the experts.
These two Pachypodium lamereis are good examples of the taller, larger Pachypodiums that are not only excellent pot plants, but wonderful landscaping plants in the right climates
Pachpodium namaquanums are incredibly bizarre caudiciforms and wonderful potted plants (first two on the left). The Pachypodium lealii however, is a much hardier, easier plant. Both of these are from southern Africa, not Madagascar
These are examples of the smaller Pachypodiums: from left to right and top to bottom: Pachypodium densiflorum, Pachypodium brevicaule (huge specimen since this is a very dinky species normally), Pachypodium makayense, and the last one is a hybrid brevicaule species
These are examples of Pachypodiums with caudiciform roots (from Southern Africa- in the wild these caudices would be buried- nearly true geophytes). The first photo is of Pachypodium bispinosum, and the other two are Pachypodium succulentum
One of the weirder genera is Pseudolithos, another member of the Asclepid family. These greenish ‘rocks’ don’t do a lot, except flower now and then… but make fascinating small, potted plants. Their care is quite specific and is not for the beginning caudiciform collector.
First two photos are of Pseudolithos species, and the last, another Asclepid member, Trichocaulon, is a very similar looking caudiciform
Pseudobombax ellipticum (often called Bombax ellipticum) is another commonly grown plant/tree, and makes a curious caudiciform with a reptilian pattern on its base. If put in the ground, this become large trees.
several nice Pseudobombax elipticum bonsais showing the ornamental caudex
Sesamothamnus are potentially massive caudiciform plants with peeling trunks and small leaves. The most commonly grown species, Sesamothamnus lugardii, is somewhat prone rot if overwatered as a seedling, but becomes more hardy the larger it gets. It is grown throughout southern California as a fascinating xeriscape plant.
Sesamothamnus lugardii potted in a show, and as a weird pachcaul landscape plant in southern California
Trichodiademas are in the mesemb family and the most commonly grown species is Trichodiadema bulbosum, an easy and attractive caudiciform that is pretty easy to find, too. This plant normally has thick, succulent roots, but in cultivation the roots can be raised up repeatedly as the plant gets older and older, making it more and more spectacular. This is a very tolerant plant of common watering abuses, and quite cold hardy, too.
Trichodiadema bulbosum is an easy succulent to grow and looks great as a potted plant with its large succulent roots raised up
There are several common and interesting Tylecodon species that are caudiciform, and some are fairly simple to grow. Tylecodon panniculata (the Butter Tree) and T wallichiana are two of the most commonly grown and make wonderful, peeling, fat-trunk bonsai-like trees with deciduous succulent leaves.
Tylecodons wallichiana and panniculata, both growing outdoors in Huntington gardens. Both are good potted caudiciform plants, as well
Some Uncarinas can be grown as caudiciforms though all are considered pachycaul trees. These are for the most part yellow- flowering Madagascan shrubs/trees (at least one species has lavendar flowers) that, if grown in shallow pots, will often form fat, succulent stems. If grown in the ground, they are less obviously caudiciform. Uncarina grandidieri is probably one of the easier ones to grow, and can even be grown outdoors in the milder areas of southern California.
Uncarina roeoesliana makes a nice caudiciform plant if kept in a pot, but if grown in the ground, like the plant on the right in the photo on the right, it does not form a caudex. Photo on left by Happenstance
Xanthorrheas and Dasylirions (Australian and Mexican Grass Trees) are also sometimes considered caudiciforms in that they develop thick, short stems topped with grass or yucca-like leaves. These are sometimes grown in large pots, but most are landscape plants and rarely seen in the cactus and succulent shows paraded as caudiciforms. But they are very attractive and interesting plants, usually grown by the same sorts of collectors who like caudiciforms as well. Dasylirions are by far the easier and more common of the two genera, and are used extensively in landscapes throughout the desert world.
Dasylirion longissimus, or Mexican Grass tree on the left, is a common landscape and potted plant. Xanthorrhoea quadrangularis on the right is one of the many Australian grass tree species.
There are literally hundreds more species of Caudiciform plants, and these can sometimes be found while browsing the Plantfiles in Davesgarden. One can also get more information about caudiciforms from the following sites: http://www.bihrmann.com/caudiciforms/ or just look up Fat Plants or Caudiciforms on the web.
Kleinia is in the Daisy family (Asteraceae) Cibirhiza is another Asclepid
Coccinea sp. Kedostris sp. (both these are in the cucumber family)
This caudiciform Pelargonium sp. below is just one of many grown and shown
Pterocactus tuberosus is a true cactus but also a caudiciform. This staged plant shows off its caudiciform roots
Pterodiscus is in the same family as the Uncarina this Sedum is related to the Crassulas
Welwitchia is a unique plant that only has two leaves and a small caudex. This is a very old plant in this photo
This Urginea, or Sea Squill, is in the Lily family