A petiole is the stalk that connects a leaf to the stem of a plant. Think of it as the leaf's handle: while the flat, green part of the leaf does the work of catching sunlight and making food for the plant, the petiole holds it in position and contains tiny tubes that transport water and nutrients between the leaf and the rest of the plant.

You can see petioles easily on many common plants. The petiole of a maple leaf is long and thin, letting the leaf flutter in the breeze. On a celery plant, the petioles are the crunchy stalks we eat: what you think of as “celery” is actually the petiole, not the leaf blade! Some plants have very short petioles that hold leaves close to the stem, while others have long, flexible petioles that allow leaves to move and reposition themselves toward sunlight. Not all leaves have petioles: leaves attached directly to the stem without a stalk are called sessile leaves.