Besides height, trees grow in canopy spread and an increased root system. How quickly they grow depends on the type of tree and whether their needs are being met.
Rate of Growth. Tree speed is classified as follows:
- Fast-growing: 25 inches or more of branch growth each year. Examples are poplars (includes cottonwood), elm, ash and silver maple.
- Medium-growing: 13 to 24 inches of growth per year. Hackberry, birch, black walnut, honeylocust, red and sugar maples, lindens and young, non-bearing fruit trees.
- Slower-growing: 8 to 12 inches of growth each year. Oaks, ironwood, Ohio Buckeye, Norway maple, and fruit trees that are of bearing age.
Within these ranges, young, vigorous trees typically grow at the upper end, while older, long-established trees might grow at the lower end of the range, or slightly slower. Plants are much like people: youth is spent growing up, while age is spent filling out.
These ranges can vary greatly depending on site, moisture and soil conditions.
Using growth rate to diagnose health. The amount of yearly growth can indicate whether a tree is healthy and happy or if it’s suffering. A healthy tree should produce growth typical of its type. For example, a healthy young poplar commonly grows about 25 inches each summer, while eight inches is fine for an oak. If a tree’s growth is considerably less than its norm, it can indicate problems.
To measure yearly growth, look at a branch. Follow inward along the twig from the outer tip to a point at which you find a raised, circular ring-like scar. That’s where growth began this past spring. The current season’s twig bark is usually quite continuously smooth until you reach the growth scar.
Many of the trees I examined the past several years are on track to grow less than the ranges listed above. Slower-than-optimal growth can be caused by dry conditions or other stresses.
If a tree is growing only a few inches during the season, the situation is more serious, especially if this continues for several years. At that point some detective work is necessary to find a cause that can hopefully be corrected.