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Trunk Flare

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The trunk flare is the part of a tree where the trunk meets the ground and flares out as the trunk transitions into the root system. You should be able to see the trunk flare and even the top of the major roots coming off of the trunk. If your tree goes straight into the ground like a telephone pole, the trunk flare is buried too deep. 

How did this happen? The most common cause is by piling mulch up against the trunk. Mulch should be applied to the roots and should never be piled up against the trunk. Unfortunately it is a very common sight around Union County to see mulch piled up against the trunk. We call this volcano mulching because the sloping sides of this mulch pile resemble a volcano and the trunk looks like it is being blasted out of the top. Ok, so maybe the term volcano mulch isn’t the best description, but this really is what its called and it’s a serious problem. 

The other way the trunk flare gets buried too deep is by planting the tree too deep. Trees should be planted so that the trunk flare is visible and matches the finished grade. You have to find the trunk flare before you plant the tree, or you don’t know if you’re planting too deep or not. If you are taking a tree right out of the pot and putting it into a hole without first digging into the rootball to find the trunk flare, chances are pretty good you are dooming your tree to a short life. 

Why is it a problem if the trunk flare is buried too deep from planting wrong or from excessive mulch? Whether its mulch or soil, roots will form wherever there is moisture. These roots increase in diameter and strangle the trunk – we call these stem-girdling roots and it’s a very common problem that leads to premature tree death. This is especially common in new housing developments. .

This link shows a tree with a nice flare. You should be able to see the tops of the individual large roots coming off of the trunk.

Here is a good 1 hour long webinar on this topic.

Here is a 10 min video of a guy using tools homeowners may have on hand to expose the root flare.

Here is a good 4 min long video on the topic as well.

Watching these things you can start to get an idea of what looks ‘right’ and what looks ‘wrong’, and unfortunately, 99% of trees in these new developments look wrong.