Focus on Flora - Evening Primrose & The Primrose Moth

Pollinators love evening primrose ( Oenothera biennis ), like the one pictured above with a Primrose Moth ( Schinia florida ).

Pollinators love evening primrose (Oenothera biennis), like the one pictured above with a Primrose Moth (Schinia florida).

Flora and fauna interactions are fascinating. Hummingbirds and nectar. Ospreys and fish. And now, evening primrose and the primrose moth. A common roadside wildflower and an uncommon pink moth. Their lives are interwoven, all while we go about our usual business. Here’s a more in-depth look at their relationship.

~Natural History of Evening Primrose~
Evening primrose has a lifespan of two years. The first year the basal leaves establish followed by blooms and seeds the next. Like the name suggests, this primrose blooms in the evening and starts to close by noon the next day. Sometimes the flower will stay open throughout the day if it is overcast. The blooms are extremely showy, lasting up to six weeks per bloom. The plant will bloom all summer long and into the fall.

Evening primrose relies on pollinators like the primrose moth to spread its genetic information.

~Natural History of Primrose Moth~
The Primrose Moth (Schinia florida) relies on evening primrose to complete its lifecycle. Adults lay the eggs on the outside of the bud, along a leaf, on the stem, or at the base of a flower. The larvae feed on unopened buds primarily, and the seed capsules to a lesser extent. They then bore a hole in the unopened bud to snack on the innards. Once they have their head inside, they will consume the unopened flower, stamen, and pistil.

Adults emerge irregularly from early July to mid-August. During this time you could potentially see several life stages of the primrose moth (eggs, larvae, and adults) on a single plant. After three days, the larvae will hatch and begin to feed on the buds. It takes about a month for the larvae to mature. At that time, they migrate to the base of the plant and burrow into the ground where they will remain until the following season.

The adults are mainly active at night (when evening primrose blooms). So, during the daytime you can often find them resting inside the delicately folded flowers.

~Pollinator Relationship~
A study released from Tel Aviv University researcher Lilach Hedany discovered that evening primrose flowers respond to bee wing vibrations. Because the flower has a bowl shape, the vibrations are amplified. This amplification leads to an increase in nectar sugar concentration. The sugar concentration is raised from between 12-17% to 20%. “A sweeter treat for pollinators, their theory goes, may draw in more insects, potentially increasing the chances of successful cross-pollination. Indeed, in field observations, researchers found that pollinators were more than nine times more common around plants another pollinator had visited within the previous six minutes.”

~Herbalist Use~
Evening primrose has a long history of herbalist use. Before it was introduced to Europeans in the 17th century, Native Americans used it as a poultice, which is a soft, moist plant material mass used to reduce inflammation and relieve soreness that is then covered with a cloth, and as an astringent and sedative additive.

Europeans used various plant parts to treat a wide array of ailments, including asthma, psoriasis, eczema, whooping cough, premenstrual syndrome, Raynaud’s Disease, rheumatoid arthritis, multiple sclerosis, and mastalgia earning it the name, “King’s Cure All.”

The oil of evening primrose is used regularly today to treat ailments ranging from arthritis to multiple sclerosis, skin disorders, premenstrual syndrome, asthma, Alzheimer’s disease, obesity, cancer, allergies, and depression. New research suggests that the plants can help recovering alcoholics by helping normal liver function resume quicker and lessen withdrawal symptoms.