Giant Mushrooms at the Base of Trees

Written by jackie carroll
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Giant Mushrooms at the Base of Trees
Mushrooms at the base of a tree indicate fungal disease. ( Images)

Mushrooms growing at a tree's base indicate that the tree is has a fungal disease rotting its roots and possibly even the trunk. Giant mushrooms indicate an advanced state of decay, and you may have to remove the tree. In rare cases, the fungus may be stopped but the damage can't be repaired.

Armillaria Mellea

The mushrooms of Armillaria mellea usually appear after heavy rains in fall or winter. They grow rapidly when the ground stays wet. When you pull back the soil and examine the trunk and roots below the soil line, you may find the wood moist, stringy or spongy. When you remove the bark, see the white mycelia, which is the vegetative part of the fungus. You may be able to stop or slow the rate of decay by removing some of the soil around the roots allowing them to dry.

Ganoderma Lucidum

Ganoderma lucidum produces reddish-brown fruiting bodies with a hard crust over the top. They appear in the summer and grow up to 14 inches across. This fungus causes rapid decay on some types of trees, such as oaks and maples, and can kill a tree in 3 to 5 years. As with A. mellea, the wood becomes spongy or stringy, and you may be able to see the white mycelia under the bark.

Damage and Symptoms

The first sign of these fungi is usually the presence of fruiting bodies around the tree. More and larger fruiting bodies indicate more advanced disease. Leaves may decline or fall early, but often the tree doesn't show any symptoms of leaf decline or poor health. There may be hollow areas or splits in the trunk. In advanced stages, limbs may fall from the tree or the whole tree may blow over because the deteriorating structure can no longer support it.


The potential danger from falling trees or tree limbs can't be overemphasised. By the time giant mushrooms appear, the tree is in an advanced state of decay. Trees in an advanced state of decay located near structures or where they put people in danger must be removed. After the tree is removed, the fungus lives in the soil, so do not plant another tree in the same location.

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