When touring children around a greenhouse or conservatory, they are often on the lookout for the weirdest, biggest, smelliest, most colourful plant. Once in a while, I might even get the question, are there any people-eating plants in here? My usual response is… not since the last student asked that question…
Remember the play, Little Shop of Horrors? If you recall, the story is about an eccentric florist who grows a plant that feeds on human flesh and blood. Although the story is fictitious, the idea that some plants can get their nutrients directly from insects or animals is not so far-fetched. There are over 600 species of carnivorous plants. Carnivorous plants refer to any plant that derives its nutrients from trapping and consuming some form of animal, insect, microorganism, arthropod or bird. Although carnivorous plants generate all of their energy from photosynthesis, most of these plants live in conditions where good root growth can be challenging: bogs, swamps, and poor soil with very little nutrients.
There are five main methods by which a carnivorous plant can trap prey.
- ‘Pitfall trap’ is the type of trap that pitcher plants use. The prey simply falls into a rolled leaf that has a pool of digestive enzymes and bacteria at the base from which the prey cannot escape.
- ‘Snap trap’ is the type where the hinged leaves snap shut when trigger hairs are touched. Note: the ‘snapping’ is not the same speed as a mouse trap closing.
- ‘Suction traps’ are modified leaves in the shape of a bladder with a hinged door that is lined with trigger hairs. Bladderworts have suction traps.
- ‘Flypaper’ or sticky adhesive traps like one would find on sundews or butterworts whose leaves are covered in glands that exude a sticky mucilage.
- ‘Lobster pot’ traps are found in plants like Sarracenia psittacina where the prey is enticed to the opening of the trap but its curiosity and desire for food has it wind its way into the cavity until it can no longer find its way out.
Various types of carnivorous plants are found throughout the world. In Saskatchewan, there are at least ten native carnivorous plants that can be found in boggy areas throughout the province. A good location to find the native pitcher plant (Sarracenia purpurea ) or the round-leaved sundew (Drosura rotundifolia) is along the ‘Boundary Bog Hiking Trail’ in the Prince Albert National Park. The 2km walking loop was closed during the last summer season due to maintenance but hopefully, the trail will be up and running for the 2024 walking season. Never remove these plants from their native habitat: they will not grow well as house plants or outside their native ecosystem.
Occasionally, nurseries and your favourite florist may have some carnivorous plants available for growing as houseplants. They can be a challenge but rewarding. Venus Fly Trap, pitcher plants and sundews are some of the more common carnivorous plants available for purchase. Venus Fly Traps have hinged leaves that are close if touched. Pitcher plants have small pitchers that produce nectar on the rim of their pitcher. As the bug searches for more nectar inside the pitcher, the bug falls into the pitcher and the smooth insides of the pitcher prevent the insect from crawling out. Sundews have sticky glands along their leaves that trap tiny insects as they land on their leaves.
Carnivorous plants are found in bogs which, in nature, are usually very sunny, and very wet and the ‘soil’ is a base of peat moss. Avoid using conventional potting soil or compost to grow carnivorous plants.
Keep the peat-based substrate continually moist by placing the plant’s container in a saucer of non-chlorinated water. The water can be changed periodically to keep it fresh. Do not use tap water (there are too many minerals in tap water) - distilled water or rainwater is best. Do not fertilize your carnivorous plant. Also, do not put dead flies or kitchen meat (like hamburger) on top of a carnivorous plant like a Venus fly trap: it will simply rot on the plant and may kill the plant.
Carnivorous plants prefer at least 6 hours of direct sunlight daily. A south-facing window in summer may be too hot but the plant will appreciate the light. The carnivorous plants that we grow as house plants prefer warm temperatures and should never be exposed to temperatures below 5°C.
Most carnivorous plants do experience a dormant period annually. You may notice your carnivorous plants slowing down their growth during the winter. During this dormant period, plants may die back. Keep plants moist during this time but consider moving them to an east or north window during this ‘rest’ period. When they are ready, they will start to regrow and can be moved back to their sunny location.
This column is provided courtesy of the Saskatchewan Perennial Society (SPS; [email protected] ). Check our website (www.saskperennial.ca) or Facebook page (www.facebook.com/saskperennial) for a list of upcoming gardening events.
