Bovine Jack

The fruit body—colloquially called a mushroom—of Suillus bovinus is a basidiocarp which is smaller and daintier than most other boletes. The cap is initially convex, then flat with a wavy margin and a grey-yellow or ochre with pink tinge in some specimens. It ranges from 3–10 cm (1+1⁄4–4 in) in diameter and has a sticky skin. The flesh is whitish, yellowish or clay-coloured and has a fruity smell. Sometimes turning a pink tinge when bruised, the flesh is spongy and rubbery. Like other boletes, it has pores instead of gills that make up the hymenophore on the underside of the cap. Suillus bovinus has a characteristic compound pore layer, consisting of an outer layer of coarse, angular pores overlaying an inner layer of finer pores. The pores are grey- to olive-yellow and generally decurrent, comprising yellow to olive-yellow tubes that measure 0.3–1 cm (1⁄8–3⁄8 in) long. The stipe is 4–6 cm (1+1⁄2–2+1⁄4 in) tall, similar in colour to the cap, and tends to be narrower towards the base. With a diameter of 0.5–0.8 cm (1⁄4–3⁄8 in), it is more slender than those of other boletes.

The spore print is an olive-brown colour. The oval to spindle-shaped spores have dimensions of 8–10 by 3.5–4.5 μm. Basidia (spore-bearing cells) are cylindrical to narrowly club-shaped, measuring 22.4–33.4 by 5.8–8.0 μm. They bear four sterigmata (each holding a single spore), which are up to 6.8 μm long. …

Suillus bovinus is found in conifer woods and plantations across Europe, including subalpine regions in the Alps, up to altitudes of 800 m (2500 ft). It is common in Lithuania, where it associates with Scots pine (Pinus sylvestris), the only naturally occurring pine in that country. Preferred soils of S. bovinus are often acidic, sand-based, or sometimes calcareous (chalky) and moraine. In Asia, it has been recorded in Taiwan, and in Japan, where it associates with Japanese red pine (Pinus densiflora). In China, it has been recorded from provinces Anhui, Fujian, Guangdong, Hunan, Jiangxi, and Zhejiang. Suillus bovinus has been introduced into other areas. In North America, where it is thought to have been introduced with Scots pine, it is found in the eastern United States, including North Carolina, Pennsylvania, Vermont, and the Adirondack Mountains of New York. It has been recorded infrequently under Scots pine in Australia, where it has been found as far north as southern Queensland, and in more southerly locations including New South Wales and Kuitpo Forest. It has been recorded in New Zealand. In South Africa, it grows with Pinus radiata.

Suillus bovinus is mycorrhizal, forming symbiotic associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue. Field work in pine forests in Sweden analysing the population structure of Suillus bovinus found that mushrooms were more abundant in younger forests and forests with disturbed areas, which contained a higher number of genets (colonies)—700 to 5700 per hectare—compared with 30 to 120 genets per hectare in mature stands. Older colonies in mature forests could be 17.5 m (57+1⁄2 ft) in diameter against 1.7–5.3 m (5+1⁄2–17+1⁄2 ft) diameter in young forests. Spore-bearing mushrooms (sporocarps) produce a huge number of spores (estimated in a Finnish study at 240 million to 1.2 billion per mushroom), of which only a small number grow successfully; this large number is thought to explain the larger numbers of colonies in disturbed and young forests, while the fungus' vegetative spread becomes more important in established forests. Colonies of S. bovinus do not overlap, which indicates they suppress each other's growth. The median lifespan of a colony was estimated to be 36 years. Field work conducted in Swedish pine forests suggested that S. variegatus suppressed the growth of S. bovinus, as there was a negative correlation in occurrence.

A Finnish study published in 1997 found that bacterial communities under P. …

Suillus bovinus tastes mild and is edible, although it is not highly regarded. When cooked, it releases a lot of fluid, which can be collected and reduced or strained to make a sauce. Its flavour is made more intense by drying. The soft and rubbery consistency of older specimens—as well as their proneness to maggot infestation—renders them almost inedible. Fruit bodies are part of the later summer diet of the red squirrel in Eurasia, which collects the mushrooms and stores them in tree forks for a ready food supply after the onset of frost. There are several fly species that often use S. bovinus fruit bodies to rear their young, including Bolitophila rossica, Exechia separata, Exechiopsis indecisa, Pegomya deprimata, and Pegohylemyia silvatica.