how pollution and landscaping are affecting urban fungi

As I walked through a local estate on one of those steely November mornings that marked so much of this fall, I was keen to see a few late mushrooms grow in a bed of bushes between the hoes.

They have been gnawed a lot by snails but are still recognizable as false chanterelles. You may know the real chanterelle. the ‘girolle’. With its beautiful egg yolk yellow and its scent like apricots, it is one of the most valuable edible mushrooms.

The false chanterelle has nothing to do with each other, but gets its name from its superficial similarities. It’s also yellow, although darker and more orange in color, and both mushrooms have so-called “draining” gills that run partially down the stem to give them a funnel-like appearance. In my opinion, the false chanterelle also has a rather pleasant and slightly fragrant smell, but is nowhere near as pronounced as the girolle.

According to my beloved mushroom book by Roger Phillips, the false chanterelle is said to be “edible but in some cases cause alarming symptoms such as hallucinations”. I have tried it only once, in the spirit of science, with no ill effects, but I have always failed to give it to my family.

Since it is primarily a coniferous forest mushroom, the surprise was not only that it grew in November, but also on an urban shrub border. The answer was quite simple, because it grew out of a mulch of wood chips, probably from a pine or some other softwood.

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The increasing horticultural use of wood chips has brought a number of new species to our cities, and I have fond memories of collecting the deliciously edible morel, a highly prized mushroom that resembles a brain on a stick, several times. Not only did I find it in parks and gardens, but once in a school playground in Islington, where I cooked it for the staff. Due to the increasing imports of exotic plants, these wood chip mushrooms even contain species that are completely new to the country. The ‘Redlead Roundhead’, for example a very distinctive species with a bright orange-red cap, came here from New Zealand and I remember finding it once in a large flower pot in the Finsbury Park branch in City and at Islington College.

Larger mushrooms like this one get their nutrients through one of three methods. The fungi on wood chips clearly act as saprophytes; Feed and break down non-living organic matter.

Fungi can also act as parasites, but most of them feed through a symbiotic process, sending out networks of underground threads that penetrate the roots of trees and then participate in a mutual exchange of nutrients.

I mention all of this because it affects the type of mushrooms you might come across in an urban area. Trees and shrubs use their relationship with fungi to break down compounds that contain organic nitrogen that would otherwise be hard to come by. However, in cities like ours, there is very high level of nitrogen deposition in the soil caused by car exhaust and other sources. This means that urban trees have to allocate more nitrogen to growth – in leaves and shoots – and store less in their roots. This in turn means that the mushrooms have less nitrogen to eat and we see fewer mushrooms producing their fruiting bodies.

There’s another property near me that has a lawn where I secretly collect shaggy ink caps every year. They first appeared in large numbers when the area was renewed.

However, they are falling year after year. I suspect that after arriving with the imported soil, they fell victim to this nitrogen problem and are unable to develop a mycorrhizal relationship with the surrounding trees.

What it shows is the fabulous and fragile network of living things and the complexity of the invisible relationships between them. It also shows the unforeseen environmental impact of our actions and how far we must go to build a city with truly biodiversity. Honestly, if it gets worse, I might have to start eating the wrong chanterelles.

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