This fungus is always associated with pine trees and emerges in huge numbers in pine forests all over the country. There are two common species, S. granulatus, the normal one where I am and S. luteus, which is more common up near Perth. The main difference is that the former has no ring on the stem.
Note 9/10/24
The species that was known in North America as S. granulatus has been re-classified as S. weaverae on the basis of genetic studies ( Mycologia, 108:6, 1216-1228) while the original S. granulatus is retained for the European species. So, it depends a bit on where our species come from originally. It is likely that it is of US origin. I often see vigorous debates online about whether something is a ‘Slippery Jack’ or a ‘Slippery Jill’ or some other common name. The fact that we can’t even be sure what we have taxonomically as a species highlights the futility of arguing about common names. S. weaverae is called ‘Butterball’ in the USA, apparently.
Although this mushroom is much collected by people of European background, and turned into pickles, it is not something that I am fond of. I find that it leaves a rather unpleasant after-taste. It is usually peeled and it benefits from drying out before use in cooking to prevent it turning into a slimy mess.
Footnote: I tried some S. luteus last night (25 April, 2010) in a kind of stroganoff. The dish was pleasant enough, but the after-taste was there again, lingering for a couple of hours. It is a pity, as these are so plentiful.
Footnote 2: 20 June 2015. The practice of peeling slippery jacks appears to have a sound basis. This report indicates that the slimy cap contains a rather strong toxin that is heat stable and not extracted by boiling water. However, not everyone reacts to this toxin. This can cause confusion as those people who are not affected often cannot understand that other people are. Some people cannot tolerate the mushroom at all and are nauseated by even a small taste. As with many mushrooms, there is a spectrum of reactions.
05/05/2024
Oddly enough, Suillus luteus is used in traditional medicine by the indigenous Saraguros people of southern Ecuador to manage gastrointestinal disorders and headaches. See also below under chemistry.
Footnote 3: 28 April 2016
There has been some suggestion that smaller specimens are firmer than larger specimens. To investigate this, I picked some fresh S. granulatus and dried them on a wire rack over the wood stove, without peeling them. The results are shown in the graph below. It can be seen that there is a clear linear relationship between the wet and dry weights and that the dry material is about 6.5% of the wet weight. In other words, they are 93.5% water. Given this result, there is no evidence that the smaller specimens are more solid than the large ones.
None of the specimens appeared overtly wet. Perhaps if there had been more rain, they might have had a higher moisture content. By comparison, oyster mushrooms are reported to have between 70 and 95% moisture content. Agaricus bisporus is reported to have a moisture content of between 88.6 and 91.3 percent. That means that the Agaricus mushrooms are about 60 percent more substantial than the Suillus.

There are quite a few different species of Suillus to be found in the pine plantations of Western Australia. These include: Suillus luteus, Suillus quiescens, Suillus salmonicolor and Suillus collinitis. There are others that are difficult to identify to species level without DNA work. Below are a few examples of some that I have found.

This one grows in one particular area of one pine forest and I have not been able to identify it. I have named it ‘silverback’ because of the silver grey colour of the cap.

Suillus species display a range of colours. This one had bright red staining on the stipe and a light blue on the flesh inside the cap.
The spores of Suillus are rather acicular. Below is an image of the spores of what I believe to be Suillus quiescens. The size is 7.1 x 2.7 microns.

Genetic variability
It is noticeable in the field that there is considerable variation in the fruiting bodies of Suillus. Two mushrooms growing right next to each other can have different appearance. A typical difference is the presence of red staining in one specimen but not in another as shown in the image below. This might be explained by the existance of genets, which are groups of mushrooms of distinct genetic origin. In the case of Suillus, this can arise from the interaction of germinating spores with existing mycelium. A genet may be a group of mushrooms or just a single fruiting body. This is explained in a this paper.
Chemistry.
One interesting compound that is found in Suillus is suillin. This compound has the structure shown below.
The structure of this compound is remarkably similar to urushiol, the active agent in poison ivy though there is no evidence that it has the same effect.
Suillin has been found to have an anticholesterinase action. This means that it suppresses the breakdown of acetylcholine. If acetylcholine is allowed to accumulate, it stimulates the muscarinic and nicotinic receptors and this can provide relief from the symptoms of Alzheimer’s disease. This is not always the case however and a study by Croxon et al suggests that it is the working, or short term memory that is affected. Existing anticholesterinase drugs such as Donepezil can cause vomiting and diarrhoea. This may (or may not) explain similar effects from Suillus.










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