Palomar Bottle Trees
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Brachychiton Spp. at Palomar College (Incl. Bottle Tree)
Australian Trees Now Placed In The Mallow Family (Malvaceae)
  Go Back To Mallow Subfamilies Page  

© W.P. Armstrong 20 June 2022
The genus Brachychiton includes some beautiful, flowering Australian trees, some with enlarged trunks called bottle trees. They are well-represented on the Palomar College campus, particularly the Queensland bottle tree (B. rupestris). This unusual growth form is often referred to as caudiciform; however, in his book "Caudiciform & Pachycaul Succulents" (1987), Gordon Rowley, places Brachychiton bottle trees under the category "pachycauls." In fact, he places them in the same chapter as the ultimate in pachycauls: baobabs from Africa & Madagascar. Pachycaul refers to trees with fat trunks, in contrast to caudiciform plants with slender, ephemeral branches arising from an enlarged woody caudex. Some definitions for pachycaul also include "few or no branches" which certainly excludes the massive pepper tree in my yard and some Brachychitons.
Another Plant In The Hills Near Palomar College That
Resembles A Minute Bottle With Some Imagination.
Images Of The Seldom-Seen, Minute Bottlewort

Two classic examples of pachycaul and caudiciform plants. Like other botanical terms, there are undoubtedly exceptions and borderline plants that don't exactly fit into these 2 categories.

Brachychiton rupestris: A Remarkable Bottle Tree Native To Queensland, Australia

Brachychiton rupestris near Cafeteria.

Brachychiton rupestris near Multidisciplinary Building.

As I have stated on other pages, distantly related plants from arid climates on our planet often have similar adaptations. This is referred to as convergent evolution. I prefer the term "homoplasy" because it includes convergent & parallel evolution, 2 terms that are often difficult to distinguish, especially in computer generated phylogenetic trees and cladograms. Pachycaul and caudiciform plants store water in their inflated stems and may resemble each other even though they belong to entirely different plant families.





Chocolate (Theobroma cacao)
Major Changes To The Chocolate Family (Sterculiaceae),
Plant Family To Which Brachychiton Was Once Placed

The flower structure of Brachychiton indicates a taxonomic affinity with the chocolate family (Sterculiaceae). DNA phylogenetic trees (cladograms) clearly show that the chocolate family (Sterculiaceae), basswood family (Tiliaceae), and bombax family (Bombacaceae) are not monophyletic. They are better treated as subfamilies within the mallow family (Malvaceae). This is similar to placing the duckweed subfamily Lemnoideae within the Arum family (Araceae).

Monophyletic: A taxonomic group that represents a single branch (clade) in a cladogram, and having a common ancestor. For example, all birds and reptiles are thought to have descended from a single common ancestor and are monophyletic. Humans (Homo) and chimpanzees (Pan) are also monophyletic.

The mallow family contains some of the most beautiful wildflowers in San Diego County and some economically important species, including cotton & okra. Now several additional economically important families have been merged with the Malvaceae, including the chocolate family (Sterculiaceae: Cacao & cola nut), the basswood family (Tiliaceae: Basswood & jute), and the bombax family (Bombacaceae: Kapok & balsa).

  The Large & Diverse Mallow Family (Malvaceae)  
More Mallows On Palomar College Campus


Flowers & Fruit Of Palomar College Brachychiton

  Identification of Fruit Types: The Follicle  


Pink Flame Tree: Lacebark (Brachychiton discolor)

Pink flame tree (Brachychiton discolor) native to eastern Australia. Each fruit (seed pod) is technically a follicle, a single seed-bearing carpel that splits open along one seam.

Pink flame tree (Brachychiton discolor) native to eastern Australia.


Flame Tree (Brachychiton acerifolius)

Flame tree (Brachychiton acerifolius) native to east coast of Australia.


You Are Probably Wondering If Any Trees In Genus Sterculia
Remain In This Genus & Are Not Changed To Brachychiton.

Putrid Flowers Of The Indian Almond (Sterculia foetida)
Stinking flowers are by no means limited to herbaceous perennials. In fact, a large rain forest tree of the Old World tropics called Indian almond (Sterculia foetida) produces masses of small, reddish-orange flowers with a disagreeable putrid stench. It was formerly in the chocolate family (Sterculiaceae), but is now placed in the mallow family (Malvaceae). Edible seeds are produced inside large, woody pods called follicles. The oily seeds are eaten raw, roasted or fried; however, if consumed in excessive quantities the seeds may have a purgative effect. The smelly blossoms leave a long-lasting, putrid scent in your carrying case or pack. This certainly happened to my backpack on a trip to the Hawaiian Islands.


Flowers and a follicle seed pod of "stinky sterculia" or Indian almond (Sterculia foetida). A. View of seeds inside one follicle (carpel). B. Flowers from the inflorescence. C. Close-up view of one flower. D. Mature fruit composed of 5 many-seeded follicles. The speciific epithet foetida is derived from the putrid odor of the blossoms. This species is also called "Java almond" and the seeds are eaten raw, roasted or fried. It was formerly placed in the family Sterculiaceae; however DNA cladistical analysis shows that it belongs in the mallow family (Malvaceae). I once placed the flowers and seed pods of this tree into a luggage bag and the putrid odor in my bag persisted for several years!

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