The Tokai Arboretum Shroom Hunt – Autumn 2021

Two dozen Mushroom enthusiasts met on Saturday 22 May to look for Mushrooms in the Tokai Arboretum. With its extensive tree collection, the Arboretum is one of the two best places (with Newlands) in Cape Town for looking for macrofungi.

Unlike animals that run around after food, and plants that sit on the ground catching sunlight, fungi are ghosts of microscopic threads living between and around soil grains (and even plant and animal cells).

Nebulous, they can be extensive and, by size and weight, dwarf what we consider to be the biggest of the big: Blue Whales and Sequoias. Individual shrooms can be as large as fields or as small as a few microscopic threads (and don’t forget the unicellular ones – for making bread and beer, and other important stuff).

The shrooms we hunt around are just the fruiting bodies: they are collections of fungal threads (hyphae) that join together to produce a structure to disperse spores. One mushroom can produce more spores than there are humans on earth, and this can disperse in the air for thousands of kilometres.

Most fungi don’t bother producing visible fruiting bodies, but the “macroscopic species” are important to humans for food and fantasy – and fatalities.

Almost all our macrofungi are aliens. They exist at Tokai as root symbionts to alien trees brought into silviculture. Because fungi can spread through soil, and interact with soil at a far finer scale than plant rootlets, it is little wonder that many plant species – pines, oaks and gums to mention a few – use fungi as their roots.

By providing fungi with carbohydrate food, the fungi can proliferate and swap nutrients in exchange. It does come at a cost though: the fungal cell walls need nitrogen – like insects, they contain nitrogen-rich chitin rather than the carbon-rich cellulose that plants use for their cell walls. (You may remember from high school biology that animals don’t have cell walls.)

In fynbos, this high cost of nitrogen in an extremely nutrient-poor soil has resulted in Proteas and Restios and Sedges dumping fungi as “roots” and developing their own specialized nutrient extractors – proteoid and caudacous roots. By contrast, our Ericas which have kept their mycorrhizae (the fungal “roots”) are runts in comparison to Proteas and Restios: spindly, small and relatively short-lived.

So that is why Fynbos is poor in mushrooms.