Celery plants are composed of roots, leaf stalks, leaves, flowers and seeds. The leaf stalk, also called the petiole, contains collenchyma tissue, xylem tissue and phloem tissue. Collenchyma tissue is made up of elongated cells full of water that provide a crispy texture and help support the plant. Collenchyma tissue is also part of the structure of the flowers and leaves.
Vascular bundles provide additional support for the plant and are composed of xylem tissue and phloem tissue. Xylem tissue carries water through the plant, and the phloem tissue carries the nutrients through the plant system. The structure of the cells within the vascular bundles, such as xylem tissue cells and phloem tissue cells, combine with collenchyma tissue cells to give the celery stalk its stiffness and crunch.
All parts of the celery plant are edible, including the roots, leaves, leaf stalks, flowers and seeds. The leaf stalk, or petiole, has a subtle flavor and crisp texture that makes it ideal for many recipes. The inner stalks, also known as the celery heart, are more tender and mild than the outer stalks.
Flowers and seeds take up to two growing seasons to produce. The seeds are edible and used as seasoning or saved for planting another crop.