A woody plant is a plant that uses wood as its structural tissue. They are typically perennial plants that have their stems and larger roots reinforced with wood produced adjacent to the vascular tissues: typically the main stem and larger branches and roots are covered by a layer of thickened bark. Wood is an adaptation that allows woody plants to grow from above ground stems year after year, thus making some woody plants the largest and tallest plants.

Definition from URL: http://en.wikipedia.org/wiki/Woody_plant