By T. Eric Nightingale, UC Master Gardener of Napa County.
"Feed me, Seymour," is a quote that often comes to my mind when I see the most famous of carnivorous plants, the Venus flytrap. This particular plant sparks the imagination because of the several small, jaw-like structures it uses to catch insects. While it may be the most recognizable of carnivorous plants, the Venus flytrap is only one of many. This mysterious form of fauna often makes me wonder just how and why carnivorous plants eat what they do.
Despite their exotic, almost alien appearance, many carnivorous plants are native to North America. They live in swampy areas where water moves constantly and slowly over sandy, nutrient-poor soil. While these plants get plenty of sunshine, their environment nonetheless would leave them malnourished if not for their clever dietary adaptions.
Carnivorous plants lure their prey using a variety of techniques such as attractive colors, smells and even ultraviolet-light emissions. Once an insect lands on the plant, the creature is usually either trapped or stuck to the leaves.
Once captured, all hope is lost. The plant excretes enzymes that slowly digest the bug, leaving behind only a crunchy mass of limbs and exoskeleton. The nutrients, particularly nitrogen, are absorbed into the plant, helping it survive its inhospitable environment.
Scientists have found that the enzymes used by the plant in this process are similar to those used by other plants to protect them from insects. They theorize that over millennia of evolution, the plants have adapted the enzymes to better serve their needs.
You may be wondering, "If these plants eat insects, how do they reproduce? Don't they need pollinators?" Yes, they do.
Carnivorous plants often employ special tactics to avoid accidently eating a friendly insect. They may vary the type of lure they use (a lure that attracts flies but not bees, for example); the timing of their bloom (such as flowering before opening for business); or simply by growing their flower structures far away from their traps. Even with these efforts, mistakes are sometimes made, and a houseguest inadvertently becomes dinner.
Perhaps because of Halloween, I found myself absorbed in morbid curiosity about these plants. Wondering about their history and how they evolved brings strange images to my mind. I like to imagine ancient carnivorous plants as big as cars, trapping and consuming large ancient animals.
While fun to think about, this scenario is unlikely. How carnivorous plant evolved remains something of a mystery as few fossils have been found. Their delicate structures do not fossilize easily. Most of our current knowledge has been gleaned from the discovery of ancient seeds and pollen.
What we do know is that carnivorous plant species evolved separately all over the world in response to similar environmental factors. This process is called coevolution. While these species may appear to be closely related, they are not.
One particularly large carnivorous plant is Nepenthes rajah, the giant montane pitcher plant. Native to Borneo, this bulbous plant lures shrews with its sweet-tasting nectar. While the shrews eat, they defecate into the pitcher, feeding the plant nutrients it needs. Nepenthes raja is usually content with this form of feeding, but will gladly dine upon any rodent that is unlucky enough to slip into the pitcher.
This information led me to wonder if carnivorous plants could be employed for pest control in our gardens. I picture a wild yet peaceful garden, guarded against intruders by an army of carnivorous plants. Flies, mosquitoes and even rats would find no comfort there, leaving me free to enjoy the fruits of my labor.
Alas, while it's easy to grow carnivorous plants (with the right preparations), they make poor exterminators. The quantity of insects they require to sustain themselves is low compared to the number of pests we wish to remove from our gardens.
Nonetheless, carnivorous plants can be a fun and enriching addition to your life. While many people think they can only be grown successfully indoors under controlled conditions, they can in fact thrive outside.
The key is to recreate their natural habitat: sunny, wet and nutrient-poor. They are so accustomed to poor growing conditions that they may die if watered with tap water. The minerals in common tap water can over-fertilize them; use only distilled water.
Workshop: U. C. Master Gardeners of Napa County will conduct a workshop on “Fruit Tree Selection and Planting” on Saturday, November 18, from 9:30 a.m. to 11:30 a.m. at the University of California Cooperative Extension office, 1710 Soscol Avenue, Napa. It's the perfect time to get the soil ready to plant bare-root fruit trees, or to plant from a pot into the ground. Learn about soil types, site selection, site preparation and first-year care. Prepare your garden now so your new fruit trees will thrive. Learn what fruit tree varieties perform well in Napa County so you can choose wisely. Online registration (credit card only); Mail-in form (cash or check only).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.