Many have asked me, if a specific plant would be classified as a caudiciform. In general, that is a hard question to answer. The original meaning of the Latin word; caudex refers to the stem-like strukture of a plant. However, the term is used for a vide range of plants these days.
Caudiciform mean stem-like, and refers to plants which have no actually stem, but form a stem-like structure like Xanthorrhoea preissii. However, in collectors use of the term 'caudiciform', it has been used for plants with any significantly swollen part of the plant.
It is then no longer a scientific definition, and that open up for interpretations and discussions. I will fare from claim that I have the answer, and I actually disagree with some of the plants on my own site being caudiciforms! I have removed a few, and I might consider to go critically through them one day. I have not done it so far, as I would hate to delete plants like Boophane disticha.

Some classifications have been made, but they only classify the plants without defining the entire group. In 1904, the Danish botanist Christen C. Raunkiær came up with Phanerophytes which are those plants who have their swollen part clear of the ground. Bear in mind; many of the plants in collections have had their caudex raised, but their visible caudex is fare from natural.

These classifications are based on the natural growing from of the plants. Chamaephytes have their swollen part just above, in or just below the soil level. Hemicryptophytes have their swollen part formed below ground, but the growing point is above ground. Some plants like Fockea edulis actually change this through their first years. Geophytes are plants that have both the swollen part and the growing point below the surface. Not that interesting for collectors, and most are raised to be exposed. Some thrive despite this alteration, others will not survive this treatment.

The collectors use of “caudiciform” might be defined a bit. I guess all will agree; it take some form of swollen part of the plant. Can it be the leaves? Well, if that is enough to classify a plant as a caudiciform, most succulents and all bulbs would be included, as the bulb is actually thickened bases of the leaves. Despite I have quite some bulbs among my pages, I have to admit; I would not really include the “fat-leaved” plants into caudiciforms.

Then there are the ones with fat branches like Plectranthus ernstii. Most have a swollen stem too, but even though they lack that, I would personally include them. If a fat stem is enough, many cacti would be included. If we want to exclude them – and I do, we have to define the swollen part should be significantly thicker than the rest. But how much thicker does it have to be?

And what about the succulents that is only forming a single sphere like Euphorbia obesa and White-sloanea crassa? I have not included them, but I do have Pseudolithos cubiformis, which is build the same way. To exclude these plants, we have to define, that they do have to have branches or at least leaves, beside from the swollen trunk. I think that will be the case.
It should be easy to agree on; a swollen base always will classify the plant as a caudiciform – or will it? Is Ariocarpus fissuratus a caudiciform? Or should it still have additional branches or leaves? Personally, I think it should.

The swollen roots might be divided into three groups: The actual roots, the rhizomes and the central, more trunk-like base. Will a plant with thickenings on the thinner roots like Pereskia diaz-romeroana be a caudiciform? And the many Asparagaceae like Asparagus declinatus which form rhizomes? I have chosen to include these, if they survive to have their swollen parts exposed.

The swollen base of the root surely classifies a plant as a caudiciform – or not? If it will not survive being exposed, it is at least not that interesting in the collection. I still think they are caudiciforms, but I have not included (many) on my site.

Then there are all the crops! Is a turnip or a carrot a caudiciform? I have chosen to disclose the annual and biannual plants, although one of my first caudiciforms (or not); Ipomoea batatas actually got its page, despite the original “potato” will only live a few years

Some plants change their appearance significantly over the years. Some form a significantly caudex in their first years like Bursera graveolens, just to lose it within the coming years. Others only form the swollen part after many years like Adansonia rubrostipa, where it can take 35 years before it starts to thicken up – just like many humans. Are they still all caudiciforms? Or should they have the caudex at present time?

If the latter is the case, some plants will only be interesting for a few years, others will never achieve the characteristics we want, before they outgrow the space we have. In general, I would say; they have to have the caudex at present time to qualify.
Some plants can form a caudex if the environment is right, or they can be pruned into it. Again, I would state; they have to have the caudex at present time to qualify.

Should the swollen part be made-up by a specific tissue? Or have a specific structure and surface? Looking down the list of accepted caudiciforms, it will be a clear “no”. As the accepted plants form the caudex different places and the plants come from so many different families, all kind of tissue is accepted.

What have we learned? Well, it is not really possible to define the common term “caudiciform”, as it has been used quite wide. Furthermore, some plants that immediately seem to be qualifying, are not generally accepted to be included.
I will leave it up the individuals to decide wherever they want to classify a specific plant as a caudiciform or not. It is an open term, free to be interpreted by the individual. If you like it: Grow it!

Xanthorrhoea preissii

Boophane disticha

 Fockea edulis

Adromischus schuldtianus

Plectranthus ernstii

Pseudolithos cubiformis

Ariocarpus fissuratus

Pereskia diaz-romeroana

Asparagus declinatus

Adansonia rubrostipa

Dioscorea mexicana