Gila/Salt Intermediate Basins

Three native milkweeds are in full flower this week—rush-desert milkweed (Asclepias subulata), Arizona milkweed (A. angustifolia), and desert milkweed (A. erosa)—all of them fruiting alongside their fresh blooms. These are perennial species that flower year-round in this region, a rhythm shaped by the Sonoran climate.

Monarchs have been sighted six times in the past two months, with the most recent appearance on June 16. That consistent milkweed availability—blooming when most temperate nectar sources have faded—may be stalling some migrants that should be heading toward California breeding grounds. Monarchs are obligate milkweed specialists at the larval stage, and abundant food here can trap individuals that would normally press northward. The ecological trade-off is real: without year-round flowering plants, this desert would be uninhabitable for the early season butterflies that do make it through, but the same abundance may be delaying the continent-wide migration cycle itself.