Arboretum Paths

Published 2:38 pm Wednesday, July 31, 2013

When visitors hear that the Arboretum has carnivorous plants in our exhibits, many assume that we have Venus flytraps (Dionaea muscipula). But while this plant is certainly popular, people are surprised to learn that it is native only to North and South Carolina.

Specifically, Venus flytraps are found in the nutrient-poor soils of wet pine savannas found in an area surrounding Wilmington, North Carolina. These unusual plants trap and digest insects that provide them with nitrogen and other nutrients for the plants’ growth. While flytraps are commonly cultivated, very small numbers are found in the wild. Pressures that contribute to their decline include development, the reduced use of fire as a land management tool, and poaching.

Early in my childhood, I remember being fascinated by the dramatic way that Venus flytraps caught and liquefied their insect prey. Like other flytrap owners, I enjoyed feeding them raw hamburger meat and an occasional fly, and poking the leaves with my pencil to watch them snap shut. If you look closely, you’ll see tiny trigger hairs on the leaf surface. When these are tripped by unlucky insects, the “jaws” quickly snap closed. Amazingly, Venus flytrap leaves are able to distinguish the difference between a drop of rain and an insect.

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Venus flytraps are in the family Droseraceae, which also includes the tiny sundews (genus Drosera) found in the Arboretum’s Savanna Exhibit. If you look at both plants, you will see that they have a similar structure. But while sundews capture small insects in their sticky “dew”, the flytraps are able to capture much larger insects in their “traps”. Some lucky insects are small enough to crawl out between the open mesh of the leaf edges.

If you have a fondness for these plants, you’ll enjoy our program this Friday on the secret lives of the carnivorous species found at the Arboretum with Senior Curator Richelle Stafne and summer intern Conner Ryan from Auburn University. We recently learned that Conner has extensively studied carnivorous species and is quite familiar with named cultivars, sources for obtaining carnivorous plants, and growing and propagation methods. He has recommended several excellent books, which we will have available at the program.

Carnivorous plant species found at the Arboretum include several species of sundew, bladderwort (Utricularia), and Sarracenia. The yellow blooms of bladderwort make it easy to locate one species of this tiny plant in the late spring, where it grows along the boardwalk. At other times of the year, it is very difficult to distinguish from its surroundings.

Another species of bladderwort is found in the shallow water of the Aquatic Exhibit near Cypress Head. The plants often form large floating mats. It’s quite a sight to see these tiny yellow flowers floating on the surface of the water. The plants have tiny “bladder” structures that have a negative water pressure until tiny hairs at the opening sealing the bladder shut are triggered by tiny insects or organisms. Then the flap springs open, causing water to be sucked in along with the prey. Once the flap closes, the insects and microorganisms are slowly digested.

Like bladderworts, sundews have a very brief time period when they will steal the show. They are very easy to pick out in the Savanna Exhibit in early spring, especially following a prescribed burn when much of perennial layers are low and the grasses have been reduced to stubble. The large areas of “bare” soil provide easy viewing of the tiny rosettes of leaves, covered with their sparkling ruby dew.

The sundews range from the size of a dime to the size of a quarter or larger. When they bloom, the thin stalks have a comical appearance, with large white blooms that seem out of proportion for such tiny plants. Children delight in pointing them out on school field trips.

The most conspicuous carnivorous plant at the Arboretum is the yellow pitcher plant (Sarracenia alata). It is found in clusters throughout the Savanna Exhibit, and is particularly abundant in the south Pitcher Plant Bog. The “lids” at the top of the modified leaves serve to reduce the amount of rainwater entering the “pitchers”, which would otherwise dilute the digestive enzymes in the hollow leaves.

Both the yellow pitcher plants and the smaller parrot pitcher plants (S.psittacina) have distinctive blooms that are held above their rosettes. The yellow blooms of S. alata are known as “buttercups” in Pearl River County. Although the parrot pitcher plants are much smaller in stature, their burgundy flowers make their cluster easy to locate in the spring.

Join Richelle Stafne and Conner Ryan on for their fascinating presentation about the secret lives of the carnivorous plants found in the exhibits at The Crosby Arboretum. Bring a sandwich and make it a date with a friend for lunch.

Children will enjoy a special field walk and clay class on Saturday, August 10. They will use self-hardening clay to make impressions of plant material collecting on their walk.

For further exploration:

Read about the various ways that carnivorous species trap and digest their prey. Research the projected number of Venus flytraps that are believed to still exist in the wild. What is being done to preserve, and increase, their populations?