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Showing posts from December, 2011

What to Do about Pot-Bound Plants

By Jeff Gillman, Associate Professor - Department of Horticultural Science

So you've just bought a pot-bound plant and you don't know what to do? Gary Johnson, Chad Giblin and I have been testing various techniques to get trees out of their pot-bound states for the last 8 years or so, and here are some of the things that we've found.

The number one problem with planting a pot-bound tree is that they are usually planted too deeply. Trees in containers often have three inches between their uppermost roots and the soil line -- or even more! When a tree like this is transplanted into a landscape without having its planting height adjusted, the roots circling near the top of the container will eventually press up against the stem of the tree and strangle it to death (photo 1).

Jeff Gillman
Photo 1: Pot bound plant's root system 5 years after planting; tree was planted too deep based on media level in pot

When planting a container grown tree make sure that the first large…

What is the true cost of planting a tree too deep?

Karl Foord, UMN Extension Educator

Karl Foord
Photo 1: Encircling root has significantly stunted this tree.
If you purchased a tree and planted it at the soil line as it was in the pot, it is likely that this tree was planted too deep - with drastic consequences. Research conducted by Gary Johnson, Jeff Gillman, and Chad Giblin has shown that trees planted too deeply tend to generate roots that can strangle the plant. Dr. Jeff Gillman explains more of the science in the following article; however in this article I want to address what I believe is the true cost of making such an error.

Karl Foord
I have two 'Autumn Blaze' maple trees that were planted approximately 10 years ago. Several years ago I checked the planting depth of the trees and discovered that one had been planted too deep (tree 1). Tree 1 had several encircling roots that severely impacted its growth (Photo 1). Tree 2 had a few encircling roots that I caught before much damage was done (Photo 2). What is the…

Bur Oak Blight

Michelle Grabowski, UMN Extension Educator

T. Harrington, ISU
Photo 1: Leaves killed by Bur Oak Blight clinging to the tree after fall leaf drop

A healthy bur oak will drop all of it's leaves in the fall. Leaves that are infected with the fungal pathogen (Tubakia sp.) that causes Bur Oak Blight (BOB) remain attached to the tree into the winter. As a result, now is a good time to examine landscape bur oaks for possible infection with BOB.

Bur Oak Blight causes leaves of bur oak trees to develop brown wedge shaped lesions in July and August. This fungal disease often starts in the lower canopy and progresses up the tree in following years. Some bur oak trees are highly susceptible to BOB. After several years of infection, the entire canopy can appear brown and scorched. These severely infected trees are weakened and often fall prey to secondary pests like two lined chestnut borer and Armillaria root rot. It is possible for bur oaks to be killed by this combination of fungal and inse…