Milkweed flowers open as monarch caterpillars emerge
May 22, 2026
The air carries a faint sweetness across the Potomac Hills neighborhood this morning, where clusters of pink and orange flowers have begun to open on the milkweed plants scattered through yards and along fence lines. Common milkweed stands waist-high with its broad oval leaves, while the lower butterfly milkweed shows off bright orange blooms that seem to glow in the early light. The timing is no accident.Monarch caterpillars are hatching now from eggs laid on these same plants just days ago. The tiny larvae, smaller than a grain of rice, emerge with an immediate need. They eat their own eggshells first, then begin the work that will define their entire existence: consuming milkweed leaves. Nothing else will do. The chemical compounds in milkweed, toxic to most creatures, become the monarch's protection. The caterpillars concentrate these toxins in their bodies, making them unpalatable to birds and other predators.This relationship runs deeper than simple feeding. The milkweed plants are now entering their peak flowering period, their blooms attracting not just the adult monarchs that will lay the next generation of eggs, but dozens of other pollinators. Bees work the flowers methodically, their legs heavy with pollen. The monarch adults, when they visit, are less efficient pollinators than the bees, but they serve the plants in a different way. By laying their eggs exclusively on milkweed, they ensure a steady population of leaf-eating caterpillars that never fully defoliate their host plants. The caterpillars consume enough to stimulate new growth but leave the root systems intact.As the caterpillars grow over the coming weeks, they will shed their skin five times, each molt revealing a larger, more boldly striped larva. The final instar caterpillars, thick as a thumb and marked with yellow, black, and white bands, can strip a milkweed plant of most of its leaves before wandering off to pupate. But the plants recover. Their deep taproots, sometimes extending six feet down, store enough energy to send up new shoots. By late summer, many of these same milkweed plants will bloom again, providing nectar for the monarchs beginning their long migration south.The butterfly milkweed, with its more compact form and brilliant orange flowers, follows a slightly different schedule. Its blooms last longer than those of common milkweed, extending the nectar season well into summer. Both species contain the cardiac glycosides that make monarch caterpillars toxic to predators, but butterfly milkweed produces less of the milky latex that gives common milkweed its name. The caterpillars show no preference between the two species, moving from plant to plant as they outgrow their current food source.In yards where homeowners have planted native milkweeds, this ancient cycle plays out just as it does in prairies and meadows. The plants ask for little: decent drainage, full sun, and patience as they establish their deep root systems. In return, they anchor one of North America's most remarkable migrations. The caterpillars feeding on milkweed leaves today will become the butterflies that travel thousands of miles to overwinter in Mexico, guided by magnetic fields and celestial cues that scientists are still working to understand.Step outside if you can, and look for the milkweeds beginning to bloom in your area. The flowers release their fragrance most strongly in the warm afternoon sun, sweet and slightly cloying. If you find a plant, check the undersides of the leaves. The monarch eggs, when present, appear as tiny white dots, usually laid singly on the youngest, most tender foliage. The whole relationship begins there, with that small white sphere and the vast genetic memory it contains.
Fireflies signal through the short summer nights
June 25, 2026
The light is still fading at nine o'clock. In the understory along Bethesda's wooded edges, where flowering dogwood and pawpaw hold the middle layer and the canopy closes overhead, the first flashes appear low to the ground, maybe a foot or two above the grass. They are yellow-green, brief, and arcing slightly upward. By the time full dark settles in, there are dozens of them.These are common eastern fireflies, and what you are watching is a conversation. The males fly and flash; the females wait, perched on vegetation, watching. The male's signal follows a precise pattern: a single flash lasting about half a second, then a pause of roughly six seconds, then another flash. The arc of the flight is part of it too. Females who are ready to mate flash back after a fixed delay, typically about two seconds. That timing is the key. Males scanning the dark learn to read it. A female who answers at the right interval draws the male toward her, and he flashes again, and she answers again, and he homes in. The whole exchange can take several minutes before the male lands.This is peak season for them. The nights are the shortest they will be all year, which means the window for signaling is compressed. But the warmth matters as much as the darkness. Common eastern fireflies are most active when air temperatures stay above roughly 21 degrees Celsius after sunset, and summer nights here hold that heat. The flashing typically begins in the first hour after dark and tapers off by midnight. On a warm, still night with low wind, the signals carry well and the activity is dense. On cooler nights, or nights with rain, it falls away quickly.The light itself is produced in the abdomen, in a specialized organ that runs a chemical reaction involving a compound called luciferin, an enzyme called luciferase, and oxygen. The reaction produces light with almost no heat, which is unusual for a light-producing process. The firefly controls the flash by controlling the oxygen supply to the organ. The precision of the timing, the duration, the interval, is all physiological, controlled by the nervous system. Different firefly species in the same habitat use different flash patterns and different colors, which is how a female tells her own species from others flying nearby. In the same meadow edge, you might have several species active at once, each running a different signal.The larvae spend most of their lives underground or in leaf litter, where they are predators of soft-bodied invertebrates including earthworms and snails. The adult firefly, the one flashing now, does not eat at all, or eats very little. The adult stage is entirely about reproduction. The females of some firefly species mimic the flash responses of other species to lure males and eat them, but common eastern fireflies do not do this. The adults live only a few weeks.
