MYSTERY PLANT: Seed pod not all that spooky
“Well, I don’t know what they are; I never saw them before. They looked like great big seed pods.”
– From “Invasion of the Body Snatchers,” 1956.
PODS FROM OUTER SPACE! I loved that old movie, “Invasion of the Body Snatchers,” from back in the ’50s. It was imaginative, fun and very creepy. I recall staying up late on Saturday nights to watch monster movies, sipping ice cream and Coke floats, with the lights off. The old black-and-white TV would churn out some real thrillers. And this movie dealt with alien plant life! (Maybe this is why I ended up studying botany.)
The weird things in this photo are indeed “pods,” if you like to use that term. Botanically, “pod” is not at all precise and means a number of different things.
“Seed pod” is a bit more on target and usually refers colloquially to any kind of ripe fruit with dry, somewhat hardened walls, which is more or less inflated at maturity, bursting open somehow and releasing various numbers of seeds.
Usually, the fruit types that fit into our notion of a “pod” are what we botanists call capsules, such as those formed by okra, lily or iris. In a capsule, there are three or more elongated, seed-bearing segments completely fused together before splitting open.
Beans are sometimes called “pods,” too; the pods on a mimosa tree are a good example. A bean contains only one seed-bearing segment, and it breaks open along two lines. A bean’s pod is technically a legume, and we refer to members of the bean family as “legumes.”
The last sort of seed pod you probably know is that of a follicle, these produced by members of several families; the milkweed family is the classic example. A milkweed’s follicle is usually tapered, with a point on one end, and similar to a legume in containing only one seed-bearing surface. Although there doesn’t seem to be much structural difference between a legume and a follicle, a bean pod (legume) splits open along two lines. A milkweed pod (follicle) splits open along only one.
Our curious little plant here is not really a monster. And it’s not from another planet. It’s from South Africa, occasionally grown in sunny gardens and at conservatories here in the Southeast. It has a greenish stem to nearly 5 feet or so and produces plenty of narrow leaves, delicious to monarch butterflies. And it is a milkweed species, so that a broken stem or torn leaf will reveal white sap. Its flowers are attractive and white, produced in characteristic rounded clusters. The fruits are indeed follicles, and, in this case, each follicle is surrounded by a thin skin, abundantly covered with soft, somewhat wiggly spines. This rounded outer layer can sometimes be nearly the size of an orange! The skin is prominently inflated around the follicle inside, which ultimately splits down one side and releases seeds in the traditional milkweed way, each seed with a downy parachute of delicate hairs.
No, it’s not really a monster, and its bizarre little pods won’t snatch you away this Halloween season. But you never know!
John Nelson is the curator of the A.C. Moore Herbarium in the Department of Biological Sciences at USC. As a public service, the herbarium offers free plant identifications. For more information, visit www.herbarium.org or call (803) 777-8196.