bluebonnet, any of several North American lupines (Lupinus) of the pea family (Fabaceae). The most famous bluebonnets are the Texas bluebonnets, which cover immense areas in southern and western Texas like a blue carpet in the spring. They include Lupinus texensis and L. subcarnosus, which are among the most popular wildflowers of the state. The shape of the petals is said to resemble the sunbonnets worn by American pioneer women; hence their common name.
Bluebonnets are typically herbaceous annuals and grow about 0.3 metre (1 foot) tall, though perennial species may be larger. They bear palmately compound leaves composed of about five silky-haired leaflets. The characteristic purplish blue flowers are usually marked in the centre with white or yellow and borne in spikes.
In some places the name bluebonnet is given to the blue cornflower, or bachelor’s button (Centaurea cyanus), and also to the blue scabious, or devil’s bit (Succisa pratensis).