Boletus luridiformis

Names

Scientific name: Boletus luridiformis

English name: Scarletina Bolete

(Previously applied scientific names include: Boletus erythropus)

Description

It's the time of year when the first flush of mushrooms and toadstools, more usually associated with the autumn, start to appear. One of the earliest and most reliable, in my experience (I have two sites where the fruit bodies regularly appear in the early summer) is Boletus luridiformis.

Big and brassy and with its very own party trick, this distinct species is given as common throughout the UK. I was surprised then to look at the NBN Gateway and find such a patchy distribution in Scotland (see map). We should be able to fill in some of these gaps over the coming season.

This species is characterised by the red stippled stipe covered in red dots looking rather like a rash (hence the common name). Look carefully to check that there is no raised network as there are other species (e.g. Boletus luridus) that have a red network on the stipe but could otherwise be confused. Red or orange pores (the ends of the spongy tubes beneath the cap) are also characteristic as is the party trick - if you cut the fungus in half (see picture below) the pale yellow flesh starts to turn dark blue within seconds (video). Sometimes it is so fast that you could almost miss the yellow starting colour! The outer surfaces also bruise blue where damaged. The colour change is a reaction of the pigments in the fungus to oxygen in the air but what the function is, if any, is unknown. Other boletes turn blue so this feature by itself does not indicate only B. luridiformis.

The cap often starts out quite velvety but as it ages it becomes increasingly shiny and can even appear slimy in damp weather. The cap colour is usually a rich dark brown and can grow up to 12 cm across.

Members of the genus Boletus are basidiomycetes and are ectomycorrhizal, always fruiting in association with a tree host. More information about some of these terms and fungal lifestyles

Fruiting:

B. luridiformis first appears in Scotland during May (one record) and then builds up to a fruiting peak in September (89 records) after which the number of records fall off rapidly with four in November and none at all after that.

Habitat:

Usually found in acidic conditions growing with a range of trees such as oak, birch, chestnut, beech and conifers including pine.

Distribution:

B. luridiformis is given as common and widespread throughout. I am sure that the distribution is not nearly as patchy in Scotland as the map might suggest.