To be short or to be tall, that is the challenge question posed by the environment on plants. Most plants grow tall so as to effectively compete with their neighbors for available sunshine. In the environment where this thistle plant was thriving there are many herbivorous grazing animals ready to nip off plant tissue they can reach. Pressed against the ground and with a barrier of very sharp needles this plant escapes that fate, mostly. Neighboring plants that might grow taller and shade it are eaten or trampled away. The questions are forever being re-asked and answered through through the amzing process of natural selection.