What large green caterpillar with a bent short yellow tail sticking up from one end was chomping away on the pink evening primroses? A hornworm. Growing in a clay pot nestled within a pot sanctuary, the plants were obviously spotted by a hawkmoth. Not the five-spotted hawkmoth. Its gigantic larva, the tomato hornworm, has diagonal white stripes along its big green body. This enormous caterpillar had eye spots along its back. Who are you? Other than being partially denuded, the evening primrose seemed fine.
Scientifically known as Oenothera speciosa, the native pink primrose originally grew from Nebraska and Missouri down to northeastern Mexico. The perennial is often called Pinklady (not to be confused with Amaryllis belladonna, often called Pink or Naked ladies), Mexican primrose, and Amapola (Spanish for poppy). Ten species of Oenothera live in Oklahoma among the eighty native species found in North America with common names of candlestick, night willow-herb, king’s cure-all, sundrops, and large-rampion.
The Oenothera family has annuals, biennials and perennials found as flowering plants, shrubs and trees growing in plains, prairies and deserts. Most species are terrestrial, but there are a few rare aquatic evening primroses. The genus name Oenothera is Greek. Oinos means wine. Thera could mean the Greek island of Thera, huntress, harvester, summer or imbibe. The story goes if evening primrose root is eaten, a person could drink more wine.
Evening primroses are biennials. First year of life is spent as a ground-level rosette of leaves. The second year the floral stalk emerges, bears gorgeous flowers, produces seeds and the plant is done. Evening primroses grow best in full sun, medium moisture, in soil with some sand that accommodate their fleshy deep taproots. The plants can rapidly colonize disturbed areas. White, yellow or pink flowers open at dusk, which explains their name and also why moths are their main pollinators. Evening primrose blooms last one night. By next morning the flowers redden, wilt and fold in on themselves. Next evening, another set of flowers will open up.
The Missouri Evening Primrose Oenothera macrocarpa ‘Comanche Campfire’ is an Oklahoma proven plant. Native to western Oklahoma, it thrives in full sun, well-drained soil and needs little moisture once established. The low-growing perennial gets 18 inches tall and sprawls out 24 inches. Great for rock gardens or borders.
Here’s something to ponder. Israeli scientists discovered the Beach Evening Primrose flowers (Oenothera drummondii) can hear. The petals vibrate when a pollinator approaches. Bees and moths do create tiny currents in the air, but their wing beats produce sound at certain frequencies. The evening primrose flower detects the frequency and excretes a sweeter nectar within three minutes. Fresh efficient nectar production. Questions: Do human noises confuse or affect the flower vibrations and nectar production? How many other flowers can hear?
To accommodate their moth pollinators, the evening primrose also produces large pollen grains attached to each other by thin sticky vicin threads which stick to the legs and bodies of hawkmoths. Fruits are capsules that release seeds usually close to the parent plant. The seeds themselves remain viable for decades!
As a matter of fact, seeds from Oenothera biennis, the familiar Common Evening Primrose with large lemon scented yellow flowers took part in a seed-longevity experiment beginning in 1879. Seeds were selected from 23 common plants, 50 seeds from each species were put into unsealed pint bottles and the bottles buried in a small sandy hill at Michigan State University. Periodically some seeds from each plant were unearthed and planted to test for viability. After 80 years, only 3 plants had seeds that germinated: curly dock (Rumex crispus), moth mullein (Verbascum blattaria) and….ta dah….common evening primrose. What a plant.
In 1870 the North American Common Evening Primrose was carried to England for medicinal purposes. It readily adapted to much of the inland climate. The South American evening primrose prefers the ocean climate and working together, the evening primroses spread throughout Europe to Japan, Australia and South Africa.
The Cherokee boiled the leaves of evening primrose to eat as greens and the roots like potatoes. The Lakota burned the seeds as incense. The Potawatomi used the plant for headaches and the tiny seeds for skin ailments. Bobwhite quail, mourning doves, goldfinches and juncos find the seeds delicious. Whitetailed deer and small mammals dine on the plants.
Hawkmoths use the tip of their tongues to detect scents, while honey bees and bumble bees use their antennae. The pollinators track down the floral signal of the chemical linalool produced by the evening primrose. The fragrance of linalool is of citrus with spice, lavender, bergamot and lily of the valley.
My pink evening primrose is one of the host plants for the White-lined Sphinx moth (Hyles lineata), often called the “Hummingbird Moth.” The moths often form groups that hover around evening flowers. They’ve been clocked at speeds up to 25 mph. The solitary caterpillar if threatened takes on the appearance of the Egyptian sphinx by raising up its head and part of its body. The curved yellow horn on its rear is simply for show. The huge caterpillar is harmless.
The big larva disappeared the next day. Somewhere it has burrowed down 1-4 inches into the ground to pupate. In two to three weeks one big moth will emerge. Up to three broods a year may happen before the last pupal stage overwinters in the ground. To think the hummingbird moth laid eggs on a clever plant that not only hears but smells.