Evidently you are referring to a Bald Cypress tree that is very near or sitting in some water. The common term for the knobby root is 'knee'. The knees develop as the tree get older and they are almost always expressed by a Bald Cypress that is in water or is flooded for several month each year. So, if you are planning to to plant a Bald Cypress in your back yard, away from standing water, you should not see the 'knees' developing in a dryer location. The 'knee' type roots are thought to develop as the tree seeks oxygen in flooded or very wet conditions.

The Bald Cypress is a very versatile tree. It will prosper in the swampy conditions of southern areas and grow quite beautifully in a yard in the northern mid-west. Another unique characteristic of this tree is that it is a deciduous conifer, thus the name 'bald' cypress as it looses it's needles in the late fall. The Bald Cypress is favorite tree of mine. It is attractive, has unique characteristics, and is quite adaptable.