The roots on plants come mainly in two different forms. Some have fibrous roots, where they are thin and spread out over an area.
If a tree or shrub has a taproot, however, the initial root (called a radicle) thickens and lengthens over time to become the one main root. They can help plants find water that is deep in the ground. A classic example of the taproot is the carrot which is a single thick root that tapers towards the end.
Since the roots go down far and can be damaged if dug up, this can make them difficult to transplant. For these, it is best to start from seed in the intended location.
Some trees and shrubs with taproots include: