Rhinanthus serotinus var. vernalis, commonly known as Yellow Rattle, Cockscomb, or Hay Rattle, is an annual herb native to grasslands, meadows, and pastures across Europe and Western Asia. It typically grows rapidly to a height of 1.5-2 feet (0.46-0.6 meters) and is known for its hemiparasitic nature, drawing nutrients from the roots of neighboring grasses. The plant features lance-shaped leaves and produces yellow, tubular flowers with a somewhat inflated calyx, resembling small rattles, which bloom in the summer and are quite showy. The flowers give way to seed pods that rattle when shaken, hence the common name.

Yellow Rattle is valued for its ability to suppress grass growth, making it useful for creating wildflower meadows and enhancing biodiversity. It is also appreciated for its ease of maintenance and for adding visual interest to naturalistic plantings. In cultivation, it requires full sun to part shade and thrives in medium or fast-draining clay, loam, or sandy soils. It is drought-tolerant once established and can be used to manage vigorous grasses in a meadow setting. However, it can become invasive if not managed properly, and its parasitic nature may impact the growth of other plants if not carefully balanced.CC BY-SA 4.0