Salvail: Tree growth depends on nutrients, micro-climate

The amount a plant grows is partly due to its genetic back ground and partly due to its location and environmental conditions.

The most commonly asked question that I hear when it comes to tree selection and planting is ‘How big will it grow?’

Well, that’s a good question but one that is not easily answered.


When we go shopping for trees and other plants we look to the tag or info sign for information to help us make a decision. Many tags are inconsistent with their information or appear to be just flat out wrong.

Once we purchase a plant and we take it home to our own unique microcosm of growing conditions then we plant them with care, the plants go into an establishment process. This process of setting out roots and adapting to its new digs is one that can take a month to over a year.

Once the plant is established it now begins to grow. The amount a plant grows is partly due to its genetic back ground and partly due to its location and environmental conditions.

A tree may grow faster or slower depending on the following:

• Length of growing season

• Ease of root penetration through the soil

• Proper or improper planting

• The ability for the root to access oxygen

• The amount of available nutrient and water

• The surface mulch (compost base or rock )

• The attention that the home owner gives (good or bad)

• The amount of precipitation that year summer or winter

• The amount of or lack of attack from unwanted critters.

And the list goes on.

So plants, like people, are a reflection of their environment and this regulates the speed or amount of annual growth and ultimately decides how big a plant may grow.

But time itself plays the biggest role. I once read on an elderberry tag that the plant would grow to six to eight feet tall by six to eight feet wide but I had clearly witnessed this species of elderberry achieve over 15 feet tall and wide.

I have also seen supposedly small trees achieve great heights.

So, once again, time plays its role.

Tags are printed by printing companies that know about computers and printing. The info that goes on a tag is put there by a nursery person who could be from any place on the planet. I wonder what time frame they were using to come up with these numbers?

Plants start out their life with very fast growth as a juvenile and gradually, once mature, slow down as they go through the years.

But even very old trees grow a little each year. We closely examined a pine that was cut down. It was almost 500 years old. The rings inside the trunk told the story of how it grew over the extended life it lived. You could clearly see good years and bad years, good decades and bad decades. The interesting thing was that the most amount of growth that the tree put on was in the last 30 years. That’s when man moved into its neighbourhood. It had had little water or nutrients up to that point. Climate change may also have played a roll.

So many factors affect how big trees and shrubs grow. What we need to think is more about average annual growth rather than ultimate height because ultimate height may actually only be limited to how long you live.