Oak milkcapLactarius quietus

The oak milkcap (Lactarius quietus), officially the oakbug milkcap in the British Mycological Society's list, is a common reddish-brown milkcap that grows only under oak. Its Latin name quietus means 'quiet', and its dull colouring makes it easy to walk past. It does have two giveaway features, though: white milk oozes from broken gills, and it has an oily smell that tradition likens to bugs, which is where 'oakbug' comes from.

How do you identify an oak milkcap? The cap is 3 to 10 cm across, usually 4 to 8 cm, convex with an inrolled margin at first, then flattened with a shallow dip in the centre and finally shallowly funnel-shaped. It's a dull reddish brown, cinnamon or yellow-brown, darker in the centre, with faint darker concentric zones or rings of spots. The surface is matt and dry, though it can look a little shiny in wet weather. The gills run slightly down the stem and are crowded and narrow, cream or pinkish buff at first, later reddish brown with rusty spots. The milk is white to creamy white, plentiful, though scant in old caps, and doesn't turn bright yellow, at most turning faintly cream. The stem is 3 to 7 cm tall and 0.5 to 1.5 cm thick, the colour of the cap and darker reddish brown towards the base, often furrowed lengthways, and becomes hollow. The spore print is cream with a slight salmon-pink tinge. The oily, bug-like smell is strongest in old or drying caps.

Where does it grow? Only under oak, which it partners through its roots: in oak and mixed woods, often near old trees, along woodland edges and in parks, in leaf litter and grass. It grows in groups from late summer to late autumn.

Is the oak milkcap edible? Sources disagree. Foraging guides call it edible but bitter and not very pleasant, while some older field guides list it as inedible. In Ukraine it's eaten only salted, after a day of soaking and fifteen minutes of boiling. We found no reports of poisoning, but it's a poor mushroom, and the real risk is confusing it with something worse.

What can you mistake it for? The most important lookalike is the poisonous yellowdrop milkcap, which grows under the same oaks. Its white milk turns bright sulphur yellow within seconds. So break a gill and wait half a minute: if the milk turns yellow, leave the mushroom alone. The fenugreek milkcap, which is poisonous, has watery, colourless milk and a strong smell of fenugreek or stock cubes, and grows under conifers and birch on wet ground. Lactarius insulsus has clearly zoned, paler caps and hot, acrid milk. The mild milkcap looks very similar but has hardly any oily smell and grows under beech. The rufous milkcap is darker, has a central bump, grows under conifers and has very acrid milk, and the curry milkcap is small, grows under pines and smells of curry. Beginners should also remember the brown rollrim: it has no milk, and its gills peel away easily and bruise brown at once, and it's dangerous, because eating it repeatedly can trigger severe, even fatal, anaemia.