Curious Cauliflory

Guarea sp. in the Mahoghany family, Rancho Naturalista, Turrialba

Guarea sp. in the Mahoghany family, a native tree in the rain forest at Rancho Naturalista, Turrialba, Costa Rica

A botanical adaptation that exists in temperate and arid woodlands, but is much more common in tropical forests, cauliflory literally means “stem flower”, or the curious phenomenon of flowers growing directly out of the bark of woody trunks and limbs. We are, of course, more accustomed to seeing flowers growing out of buds at the end of leafy new growth on trees or bushes. In Costa Rica, my encounters with examples of cauliflory have been more frequent than I realized: a recent review of my photo files revealed cauliflory as a fascination of mine for some time.

Calabash, the Gourd Tree, here called Jicaro (Crescentia cujete)

Calabash, the native  Gourd Tree, called Jicaro in Costa Rica (Crescentia cujete)

One of my heroes, Dan Janzen (see previous Foto Diarist post on caterpillars), posited along with his colleague, P.S. Martin, that cauliflory existed since pre-Pleistocene times (2.6 million to 11,600 years ago) in the bat-pollinated calabash tree (commonly seen in two gourd species native to Costa Rica), and that the fruits were probably eaten–and their seeds dispersed–by elephant-like mammals, now extinct, called gomphotheres.

In evolutionary terms, there are reasons cauliflorous trees and shrubs have successfully survived the ages: their flowers are visited by many different animal species, including birds, arboreal mammals, bats and insects. It is apparently the accessibility of the flowers and seed-producing fruits that accounts for cauliflory’s persistence: in many instances, the tree or shrub grows to heights well below the forest canopy, so the pollinator or frugivore (fruit eater) doesn’t have to climb or fly very high. According to plant evolutionist G. Ledyard Stebbins, the adaptive importance of cauliflory appears to be primarily associated with cross-pollination. Since most species’ flowers are not self-pollinated, they must be visited by animals, birds or insects, and if more than one species is involved, so much the better.  Tropical researchers, especially entomologists, have learned that insects of rain forests are distributed in horizontal layers at various heights above the ground. In many cauliflorous species, such as Theobroma cacao, from which we get chocolate, it is the

Flowers of Theobroma cacao growing from main trunk of a small tree at Finca Cantaros. The seeds, when dried and ground, produce chocolate.

Flowers of Theobroma cacao growing from main trunk of a small tree at Finca Cantaros. Cacao is pollinated by Ceratopogonid midges in the order Diptera. I believe the insects seen on the flower stem are aphids.

Theobroma cacao, chocolate pod growing on trunk a few feet from the ground.

Theobroma cacao, with immature pod growing on trunk a few feet from the ground. When dried and ground, the seeds produce chocolate. Note tiny flower buds, upper left.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

insect fauna crawling and flying near ground level that performs much of the pollination. Tiny midges do the primary work for the cacao, but other crawling insects are believed to be involved.

Especially common cases of cauliflory in the new and old world tropics are found in edible fruits: jackfruit, breadfruit, star fruit, figs, cherimoya, soursop, some water apples, and one species of papaya, to name a few.

At Finca Cántaros, we take particular pleasure from our small orchard of Jaboticaba (Plinia cauliflora), a shrub native to Brazil. The delicious dark cherry-like fruits are abundant on the trunk and limbs around late March and early April, when I enjoy making beautiful purple sorbets and smoothies.

February flowers of Jaboticaba tree

February flowers of Jaboticaba tree

Fruits of Jaboticaba tree, Finca Cantaros

April fruits of Jaboticaba tree, Finca Cantaros

 

 

 

 

 

 

 

 

 

 

 

 

The Cannonball Tree, Couroupita guianensis. Large flowers develop on woody stalks on thick bark of main trunk and limbs. The round fruits are heavy and grow to 8 inches in diameter.

The Cannonball Tree, Couroupita guianensis. Large flowers develop on woody stalks on thick bark of the main trunk and limbs. The round fruits are heavy and grow to 8-10 inches in diameter as high as 100 feet. Native to South America and Trinidad, this immense and magnificent specimen is on the big island of Hawaii, photographed at the Hawaii Tropical Botanical Garden. It is pollinated by bats and Carpenter bees.

 

Note:  A Chinese Proverb says that calling things by their proper names is the beginning of wisdom. This suggests that if you know the correct name for an animal, plant or even a plumber’s tool, you narrow the distance between that being or object and yourself. Latin names are more accurate than popular names, so I will be using both at times in my posts, but the former in moderation. Some of my readers may find Latin names an interruption in the flow of the reading; others may want scientific names for everything. I’ll be trying to find a good middle ground on this issue.

References:

Limoncello (Siparuna thecaphora) a native shrub whose fruit are food for many bird species

Limoncello (Siparuna thecaphora) a native shrub at forest edges whose fruits are food for many bird species

Five Decades with Tropical Fruit, A Personal Journey, by William F. Whitman, published by Quisqualis Books in cooperation with Fairchild Tropical Garden, 2001.

Newsletter, Hawaii Tropical Botanical Garden, August 2014. (Not available on line).

Armstrong, W.P., 1998. The Truth about Cauliflory, accessed 8/28/15.

Daniel Janzen, Costa Rican Natural History, 1983. University of Chicago Press, Chicago (pp. 81-83).

 

 

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