Apical and Lateral Growth of Plants

Q: When trees grow, do they grow bigger around and then get taller or do they grow tall and then get bigger around?

A: A plant grows new tissue from an apical meristem. The apical meristem is a group of cells that retain the ability to continue divisions, forming new cells continuously as the plant grows. This PRIMARY growth is responsible for growth in height. Woody plants have SECONDARY growth, in that they have a special lateral meristem called the vascular cambium, that allows for growth in diameter. The cambium makes large cells early in the year, and smaller ones later in the summer, and this cycling of large and small cells is responsible for the appearance of growth rings in the wood, usually 1 "ring" per year. So the answer is that they grow taller, then get bigger around.

Q: Lets say you carved your name in a young tree about 10 feet in height, with your name being about 4 feet from the ground. When the tree grows to be 250 years old, how far would your name have gone up the tree or would it still be in the same spot.?

A: I used to ask my students this same type question on tests, except that I used driving a nail in the tree as an example. Because of what I told you in the answer to question one above, you can see that your name would still be in the same spot (4' tall) except it would be overgrown by bark as the tree grows in diameter.

Q: How old is the the oldest oak tree and how big is it?

A: Don't know the precise answer to that. The oldest trees are actually bristle cone pine trees rather than oaks, and some of the oldest are over 5,000 years old. I'm guessing that the oldest oaks are in the range of 200-400 years old. One of the largest I've seen is a live oak tree in Jacksonville, Florida with a branch spread of about 200 feet, and a trunk diameter of about 6 feet.