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Biodiversity Blog


The Trees of BFL: Pecans (Carya illinoiensis)

 One of the burried pecans. 

Pecan trees (Carya illinoiensis) generally live along river bottom forest, or in places with irrigation systems. You may even have one or two growing in your yard. At Brackenridge Field Lab, the pecans here have a unique relationship with the history of the field lab.

In this article “The Dam that Broke,” we explored some of the prehistory of BFL. The breaking of the Austin Dam in 1900 altered much of the landscape of the area, and Brackenridge Field Lab as it was then did not escape the Tsunami and all things it carried with it.

Silt deposits covered much of the area surrounding what used to be the Austin Dam. Most plants were completely smothered, save for several older trees. Some perished, but surprisingly, quite a few lived. These include some of the pecan trees currently at BFL. Over time, erosion has exposed these pecan trees to show the depth of the sediment deposit. It reveals they were large trees at the time of the dam break in 1900, in order to have survived such a catastrophic event. This would suggest these pecans are likely nearing 250 years of age. 

Generally speaking, pecans can grow to be 75 to 100 feet in height, but overachievers have been recorded to 160 feet tall. They are native to Texas, with northern range limits in easternmost Iowa and Illinois, and also occur to the south in Mexico.

Pecan leaves are medium green, odd-pinnate, compound leaves, with each leaf having 9-17 pointed leaflets. Leaflets range from 2” to 7” long. During summer, leaves turn a yellow green, and then in fall, they turn yellow brown (pecans are among the earlier trees to lose their leaves). They are monoecious (meaning both the male and female reproductive systems exist on the same plant) and flowers appear in spring. The male inflorescences look like tassels (of numerous small flowers), and are about 4” long. The tiny female flowers are grouped into short spikes. Eventually, on trees that are at least 8-10 years of age, those female flowers give way to sweet, edible nuts beloved by animals and humans alike. There is a lot of variation in nut size, especially in wild trees.

 Erosion area exposing depth of burried pecan.

Pecans are an important commercial crop. The wood can be used for furniture, flooring, and for smoking meat. 

The word “pecan” is of Algonquin origin. The Algonquins used the word generally to refer to a variety of walnuts, hickories, and pecan. It is interesting that the range of the Algonquin tribe just barely overlapped that of the pecan. The Latin species name is from an old term, Illinois nuts, and refers to the region where traders found wild trees and nuts. It’s possible that the range of this tree has been extended through Native Americans planting it. Spanish explorers in the 1600s were so impressed by the flavor of the nuts that they collected fruits and brought trees into cultivation in Europe, Asia, and Africa.


 Photo of Austin Dam break, 1900.
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