The Original Mystery Plant
Dr. John Nelson

Photo by John Nelson

The mystery plant looks a lot like a pecan tree, but there are a number of features that distinguish the two. Of course, both pecan and the mystery plant are special kinds of hickories. Both are related to walnuts and belong to the large family called the Juglandaceae.

The mystery plant is a tree, and a potentially large one that is up to nearly 100 feet tall and big around at the bottom. Large trees have prominently shaggy bark. It likes to grow in wet places, and in particular, within the deepest, wettest portions of many of our swamps, often overhanging riverbanks.

Long- standing flooding periods are no problem for the mystery plant. It's a natural resident from the lower end of the Ohio River Valley (as in southern Illinois), down the Mississippi to the Gulf, and over to north- central Florida, and strictly along the coastal plain of Georgia and the Carolinas up to eastern Virginia.

Its leaves are compound, like a pecan's, but without quite as many leaflets. The leaflets tend to be dark, shiny, and green, They are a bit curved or falcate and finely toothy along the margins. Of course, the leaves are deciduous, and in the middle of the winter there won't be any visible leaves.

A given tree will produce both male and female flowers. The male flowers are tiny and put together into greenish- yellow, wiggly spikes that dangle from the branches.

Female flowers aren't much bigger but are produced in small clusters. This species is a member of a broad class of plants that is wind- pollinated, which makes sense when you look at the flowers because they aren't very attractive to flying insects.

After pollination, the ovary of the female flower swells dramatically, ultimately producing a thin shelled, greenish- yellow fruit. A single kernel lies within the relatively thin husk, or fruit wall, which develops.

Botanists like to think these fruits aren't true nuts, but are technically put together more or less like a drupe, which resembles an avocado or peach. This husk splits along four lines nearly down to the base. Of course, with pecans the husk divisions split all the way down and fall off. That's why you will see the bare pecan on the ground.

Additionally, the fruit produced by the mystery plant is a bit more flattened than a real pecan, and its fruits are bitter and not very good to eat, at least by humans. Answer to this week's mystery plant [Answer: "Water hickory," Carya aquatica]

Dr. John Nelson is the curator of the USC Herbarium. To learn more about the Herbarium, call 777-8196. The

department also offers free plant identification.

www.herbarium.org