Where there is cool, wet weather, there are wood rots. Questions coming in to the Master Gardener Help Desks reflect an increase in concern by gardeners. Spring and late summer/early fall are the prime times for decay fungal growth to be visible as mushrooms of all sizes, shapes and colors.
Wherever there was an ash tree removed, you will see mushrooms coming up in the lawn as the decay follows the path of the tree root. This happens even if the stump was “ground out.” Finding a mushroom growing out of an area of decay on any kind of woody plant on the trunk suggests that the internal dead woody tissue has been invaded, and that decay will likely continue. Eventually, this internal decay will weaken the structural integrity, and whole branches – or even the tree – will come down in a storm due to weight from snow or rain and/or the directional force of the wind. Most of the pictures on the news of trees having fallen after a storm can be traced back to decay in the canopy, trunk or root crown.
This time of year, mulched beds can become quite colorful as orange, yellow and other colors of slime mold work their magic on the naturally decaying organic matter. Slime molds can show up overnight and be several inches to a foot or more in diameter. They will disappear just as quickly. Don’t worry – that mulch used to be woody plants so having slime molds show up is logical.
That said, one of the worst places to for tree injury is on the trunk at the soil line, especially a young tree. There are plenty of soil borne rot fungi just waiting to invade damaged tissue. But mulch does provide a young tree benefits during transplant recovery, and it keeps away the deck of the mower and the string trimmer.
While not woody in nature, the excessive thatch layer in the lawn is organic and can support mushrooms quite well in periods of extended moisture and cool weather. Those mushrooms may go unnoticed due to their small size. One exception is Fairy Ring, a potentially large circular patch with mushrooms growing at the perimeter as it consumes more thatch. Slime molds are not limited to the mulch either; they can and do show up in the lawn, usually on the leaf blades and having a pinkish red color.
In mulch, slime molds can be managed by breaking up the mulch and letting it “air out,” eliminating the necessary environment that allows slime molds and other decay organisms to establish. Managing the thatch layer in the lawn will limit mushroom growth and benefit the overall health of the lawn.
While trees can continue to grow with internal decay for decades, those nearest to structures should be monitored, and when the threat becomes large enough, proper pruning and perhaps removal will be the only way to keep your home and belongings safe.