An Introduction To Backyard Fungi

By way of introduction to the gallery of fungi described in other postings listed under Fungi on this website, I present a brief elementary overview of the two main functional types. Unless specifically noted, all of the fungi photographs presented on this website depict uncultivated specimens growing in my central Florida yard. None have been transplanted. I assume that most if not all of the photographed species arose from spores produced by naturally occurring fungi.  Even the dead wood in the yard on which many fungi species grow originated from yard trees. It is of course possible that spores arrived in the yard from fungi growing outside of the yard.

Mycorrhizal Fungi

Strobilomyces, a mycorrhizal pore-bearing fungus

Strobilomyces, a mycorrhizal pore-bearing fungus

Strobilomyces cap from above.

Strobilomyces cap from above.

Mycorrhizal fungi are ancient plant mutualists, i.e.  they are engaged in a mutually beneficial physiological relationship with plants, and have been for eons.  Mycorrhizal fungi produce basidiomata (“mushrooms” or fruiting bodies) like other fleshy fungi. These can be found in walks through the woods or even in yards and fields. Some species are edible while others are  highly  poisonous to humans. The mycelia (the thread-like filaments that make up the vegetative, below-ground phase of  fungi) absorb minerals like phosphorous and nitrate from the surrounding soil which then become available to the “host” plant ( usually a tree or shrub). In exchange  fungi obtain  organic carbon from the host which the fungi then metabolizes for energy.  The carbon can be traced back to the host’s foliage which has converted atmospheric carbon dioxide to organic carbon compounds by means of photosynthesis.  Mycorrhizal fungi  are widespread and form associations with most terrestrial plants. One estimate is that perhaps 80% of all vascular plant species are mutually involved with mycorrhizal fungi!  The mycorrhizae enable plants to colonize nutrient-poor soils that would otherwise be less favorable for plant growth.  Most of our crops also benefit from mycorrhizal fungi thus incorporating  land areas into cultivation that would be otherwise inadequate for human food production. Interestingly, mycorrhizal fungi generally do not occur independently of host plants and in fact, some are found only in association with a single tree species.

Two species of saprophytic fungi growing out of a oak log cut as living wood about 2 years previously.

Two species of saprophytic fungi growing out of a oak log cut as living wood about 2 years previously-a gilled fungus to the left and a poroid species to the right.

Saprophytic Fungi

This group of fungi inconspicuously carries out the vital function of  recycling of nutrients through the decay of  wood and other plant tissues. Below is a photograph of a colony of Armillaria tabescens.  a saprophytic gilled mushroom  that developed  from an expansive growth of mycelia that sprang from underground roots of a red maple in our back yard.  Unfortunately for the maple, the mushroom is an aggressive invader of living and dead trees, and can be an important agent in the decline and mortality of forest trees. In cases where the fungus attacks living trees, they would be designated as parasitic rather than saprophytic.  The host red maple  is in decline, with dead main branches, a well-thinned canopy and  sloughed-off  bark at base.  Downy and Red-bellied Woodpeckers are frequent visitors and the former species successively (and exhaustively) excavated a nest-hole in a secondary (dead) branch.

Armillaria colonies at base of infected red maple

Armillaria colonies at base of infected red maple

The tree has hosted multiple colonies of  A. tabescens for at least 5 years, but likely was under siege via root-rot, for longer. Other fungi such as the oyster mushroom (see banner above) have appeared but only the Armillaria  has appeared predictably every year.  The Armillaria colonies occur mostly in autumn,  quickly passing through the above-ground phase in 1 to 2  weeks, and often first  seen in a small  “button” phase,  although undoubtedly close inspection (hands and knees) would have revealed even smaller stages.  Several days later the  button stage has expanded into  fully opened nearly flat caps with exposed gills filling the underside of the cap and producing countless spores.  See the Armillaria tab for more photographs of this colony.

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