Poor quality trees have shorter lives

The average life expectancy for a tree in urban landscapes is seven to 10 years. While there are many reasons for this sad fact, some of the problem can be traced to planting poor quality trees. I want to give you three essential rules to follow when you buy your garden’s next tree.

The first rule: Think small. A small tree, one inch or less in trunk diameter, will become established in the garden in one year, i.e. it will take one year for the tree to replace the roots that were lost during harvesting and planting. With one year of establishment period required for every inch of trunk caliper, a tree with a 6-inch trunk would take six years to establish.

Why is minimizing the establishment period important? Damaged and lost roots limit tree growth and make the tree more susceptible to drought, often resulting in branch dieback. Even drought-resistant varieties need to be watered every week during the establishment period, particularly during summer droughts. Planting a 6-inch caliper tree means six years of attention to this need.

In the long view, planting large trees is a waste of money, something that can be shown experimentally. Plant two trees in the same landscape, one with a 1-inch trunk, the other with a 6-inch trunk, and measure their growth over 10 years. At the end of this time, both trees will be about the same size. Cut the trees down and look at a cross section of the lower trunk. You will see that for the first six years, growth of the larger tree was slower than that of the initially smaller tree.

So save some money. Buy the smaller tree.

The second rule: Avoid purchasing a nursery-pruned tree. Knowing that most people are more likely to buy a young tree with lots of branches, growers prune back the leader of a young sapling during production to promote branching. However, this results in a tree with extremely crowded branches, an unnatural growth habit that will cause serious structural problems down the road. As the crowded branches grow larger in diameter, they exert pressure on each other, becoming weak and susceptible to breakage when loaded with ice or snow.

Branches on large trees should be at least 18 inches apart in a spiral arrangement up the trunk; nursery-pruned trees often have branches only a few inches apart on each side of the trunk. Your only recourse with a nursery-butchered tree is to remove competing leaders and the excess scaffold branches so that each has space to develop properly. The resulting tree is often disappointing.

The third rule: Look at the roots. The future of a young tree is determined by the quality of the root system, yet most buyers ignore the roots when selecting a tree. Gently remove the small tree from its container and inspect the root ball. If you see a mat of circling roots along the sides or bottom, pick another tree; chances are good that this tree has been in its container for too long. While the tree can survive with constrained roots under the intense management practices of the nursery, it will struggle in your garden, and those circling roots often end up girdling other roots.

Yes, applying these three rules makes buying a tree a more complex process. Part of that process is selecting a nursery that understands these issues and strives to sell only quality trees, young trees with proper branch spacing and healthy root systems.

Next week: Tips for tree care during and after planting.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to reesermanley@shead.org. Include name, address and telephone number.