Beardtongue and the bees of late spring

The morning light catches the purple throats of Front Range Beardtongue (Penstemon virens) scattered across the foothills above Boulder. These native wildflowers stand in loose clusters, their tubular blooms opening wide in the warming air. If you are walking these slopes now, you might hear the low hum that signals peak flowering season has arrived.

Front Range Beardtongue blooms in late spring when the soil has warmed but before the summer heat sets in. Each flower is a precise tube, deep purple fading to white at the throat, with four stamens tucked inside and one sterile stamen that gives the plant its common name. The bearded tongue. This architecture matters. The tube is exactly the right depth for the native bees that have evolved alongside these plants. Long-tongued bees crawl inside to reach the nectar, picking up pollen on their backs as they work. When they visit the next flower, they carry that pollen with them.

But other insects arrive at these blooms too. Seven-spotted Lady Beetles (Coccinella septempunctata), invasive from Europe, climb the flower stalks hunting for aphids and small insects that feed on the beardtongue. These red and black beetles move differently than the bees. They walk across the flower faces, occasionally picking up pollen on their hard wing covers, but they are not efficient pollinators. Their legs are too short, their bodies too smooth. They take what the plant offers without giving much back. The native bees, meanwhile, have branched hairs that trap pollen and bodies shaped by thousands of years of mutual adaptation with plants like this one.

The beardtongue depends on this late spring timing. It flowers after the last frost but before the mountain summer drought begins. The plant puts everything into this brief window, producing nectar rich enough to fuel the native bees through their own reproductive season. Leafcutter bees, mason bees, and sweat bees all visit these purple tubes. Each species works the flowers slightly differently, ensuring that pollen moves between plants scattered across the rocky slopes. The beardtongue, in turn, provides protein-rich pollen when few other native flowers are blooming. This exchange sustains both the plant and its pollinators through the narrow corridor of late spring.

The invasive lady beetles benefit from this system without contributing to it. They hunt among the flowers, taking advantage of the insect activity the beardtongue attracts. This is how invasive species often establish themselves, not by replacing native relationships but by inserting themselves into existing ones. The beetles do not harm the beardtongue directly, but they do not help it either. They are ecological freeloaders in a system built on reciprocity.

Step closer to a patch of beardtongue if you find one blooming near you. Watch for the difference in how insects move across the flowers. Native bees disappear completely into the tubes, emerging dusted with pollen. Other visitors stay on the surface, taking what they can reach. The plant has evolved to reward the bees that serve it best, hiding its nectar deep enough that only the right partners can reach it. In the warm afternoon air, you can hear this ancient partnership at work in the steady hum of wings moving from flower to flower.