The rate of tree growth depends much more heavily on the site than it does on the species. If you'd like to know how fast your trees are growing, there are a couple ways to figure this out. The first (and most time-consuming) method is to measure the DBH (diameter at breast height, 4.5') of your trees. This can be done by measuring the circumference with a flexible tape and dividing by pi. Next, measure the height of the trees. This is more complicated, and is best done with a hypsometer. There are many types of hypsometers; I use a clinometer. For mature trees, you can just guesstimate the height, and assume that it is not changing (because it probably isn't). Using the diameter, the height, and a species-specific volume equation (which many members of this forum could direct you to), you can determine the total volume of your trees. Wait 1 year, and repeat. Find the difference between the two volumes. This will provide a rough estimate of annual growth, but it will be inaccurate if the previous year was unusually wet or dry. The more years you can average, the better the estimate will be.

The second method is to determine the amount of diameter growth over the last few years by taking a sample of the growth rings at breast height. This is best done with an increment borer, which removes a small, straw-like section of wood from the tree, and will not damage the tree. Next, measure the DBH, and subtract the width of the previous year's ring x 2 to get the previous year's DBH. You can go several years back like this. Unfortunately, you will not be able to measure the previous years' heights, but for mature trees, this won't matter much. Find the volume of the tree this year, and in the past, say, 5 or 10 years. Find the average growth per year.

Pretty complicated, huh?