Shoots Growth and development Seedlings that typically germinate in late fall or early winter overwinter as basal rosettes .
Rosettes develop slowly throughout the early spring.
In the Central Valley and foothills of California, shoot bolting typically occurs in early summer and by mid-summer spines appear on developing seedheads. At the more mature stages of development, the pubescence and waxy grayish coating on the foliage of yellow starthistle reflects a considerable about of light. This reduces the heat load and the transpiration demand during the hot and dry summer months. These characteristics, as well as a deep root system, allow yellow starthistle to thrive under full sunlight in hot and dry conditions. Vigorous shoot growth coincides with increased light availability due to senescence and desiccation of neighboring annual species.