Honey Fungus – The Mushroom Diary – UK Wild Mushroom Hunting Blog

Following on from my previous post covering the Honey Fungus, I felt the need to feature this common and equally destructive Armillaria species. Again, it’s cap is variable and looks very similar to the standard Honey Fungus, but with a few distinctive visible differences.

The Dark Honey Fungus (Armillaria ostoyae), like A.mellea, often grows in large, clustered groups on or around deciduous and coniferous tree stumps, logs or even shrubs. It can fruit early, in the summer months and continue to do so up until early winter. Sometimes it appears as if growing on soil or grass, but they are actually fruiting from dead roots underneath the soil.

At first glance, the Dark Honey Fungus looks pretty much the same as the Honey Fungus as it has similar cap colouring, ranging from yellow-brown to dark brown, although they are more often darker brown. As mentioned, shapes are a little variable, with some rounded and others wavy and/or with a central depression or shield shaped. This is dependent on age also. Caps can also grow slightly larger; up to 15cm across.

The scales (or fibrous flecks) on the cap surface are much more prolific at the centre, and are a much darker brown. A decisive key difference when compared to the A.mellea can be seen on the bottom/edge of the ring, high up on the stem. If you look closely, there are dark brown markings at the edge whereas they would be pale yellow on A.mellea. So take a close look as this will aid in identification.

Safe to eat?

Most consider this fungus edible but must be cooked well and only a little tried first as it can cause stomach upset for some people. Because of this, some experts believe it to be poisonous and not worth trying.

Strange but true!

And just before I sign off, here’s an interesting titbit for you; A new record holder for the title of the world’s largest known organism was recently discovered in 1998. It was actually a Dark Honey Fungus (Armillaria ostoyae) covering approximately 2,384 acres of soil in Oregon’s Blue Mountains, USA. Based on its current growth rate, the fungus is estimated to be 2,400 years old but could be as ancient as 8,650 years, which would earn it a place among the oldest living organisms as well. Read more here: www.bbc.co.uk/earth/story/20141114-the-biggest-organism-in-the-world

Dark Honey Fungus – Armillaria ostoyae. Notice the dark brown flecks covering the cap (densely packed at the centre) and the dark markings on the edge of the whitish ring.

QUICK ID TABLE: DARK HONEY FUNGUS Armillaria ostoyae

CAP / FLESH

3-15cm across. Variable shaped; rounded to shield shaped. Covered in dark brown fibrous fibres/flecks.

STEM

6-15cm x 0.5-1.5cm. Whitish/Yellowish. Darker reddish towards base. Whitish ring with dark markings at edge.

GILLS / SPORE PRINT

Initially white, then yellowish, then pinkish/brown with darker spotted areas.

Spore Print: Pale cream (see how to take a spore print here).

HABITAT / SEASON

In clusters on or around stumps and trunks of deciduous and coniferous trees & shrubs. Summer to early winter.

EDIBILITY

Debatable. May cause gastric upset in some. Must be cooked.

The Genus ARMILLARIA (Honey Fungus): Characteristics to look out for:

• Medium to large fruiting body in large tufted groups, fused together at the base.

• Yellow-brown, Orange Brown, Dark brown colours / Round, Shallow domed to wavy shapes.

• Dark flecks or small scales on cap head, especially at the centre.

Right now at the time of writing, these medium to large mushrooms are out there in force. Large, dense groups swarm around tree stumps or at the bases of living deciduous and coniferous trees.

The Honey Fungus (Armillaria mellea) or Boot-lace Fungus (for reasons I’ll explain later) can appear early in the season, from summer onwards straight through to early winter. I usually find them on the cusp between summer and autumn – although this may be just coincidence.

It is a dangerous parasitic species of trees and plants (of which there is no cure). The exchange of nutrients between the fungus and tree is an extremely bias one, in favour of the fungus as it takes more from the tree than it gives back, causing white rot and eventually killing off the host tree. Much timber is lost every year due to Armillaria mellea and is a great danger, not to mention being a horticulturists worst nightmare!

However, they are impressive mushrooms to behold when in many numbers (which is often). Enormous groups can cover large parts of a tree, sometimes in clusters of up to (and over) a hundred at any one time. Very impressive indeed.

When young, the shallowly domed caps are honey coloured with tiny, darker coloured fibrils covering the surface, especially at the centre. As they grow and the cap expands and is variable in shape, ranging from broadly convex, depressed at the centre and often wavy and irregular at the margin. The colour is not so intense with age, they are more yellow/ochre almost always with a darker centre, retaining some of the fleck-like scales on the surface.

The long whitish-yellow stems are darker reddish-brown towards the base where several stems all fuse together. Whitish fibres can also bee seen vertically streaking along its length. The whitish ring, high up near the cap has a yellowish tinge and the white gills soon change to pale yellow, often becoming blemished with darker spots as it ages.

Fit to eat?

Just in case you’re wondering the ‘Honey’ reference defines the colour of the cap and not the taste. That may be obvious to many, but I just wanted to set the record straight! However, they are an edible species and MUST be cooked before consumption. They aren’t for everyone though, some people can suffer gastric upset, so if you intend on eating any always try a small portion first to see how you get on. If you do alright, try this great little recipe here: Spaghetti with Honey Fungus. Simple and tasty.

Honey Fungus and their Boot-laces!

Just like something out the ‘Day of the Triffids’, this fungus spreads to infect new trees by means of black cords called rhizomorphs, made up of parallel hyphae (the branching filamentous structure of a fungus). They resemble long black boot-laces (hence the use of the common name), creeping long distances to reach neighbouring trees. Rhizomorphs can be seen on roots or in the soil, but older boot-laces are often noticed under the bark of infected trees (see image below).

For the horticulturalist…

I’m no expert in the field of horticulture or anything similar, but I do know what a threat they can be for many trees and plants. If you’ve stumbled across this page looking for some answers in the removal or prevention of this fungus, here’s some good links to point you in the right direction:
• Royal Horticultural Society – Honey Fungus – Facts, symptoms and control
• Preventing garden pests and diseases – Honey Fungus (half way down the page)
• Garden Forum – Horticulture – Honey Fungus (half way down the page)

Honey Fungus (Armillaria mellea) often grow in large clustered groups. Notice the difference between the younger (bottom right) and older examples.

Top: Picture courtesy of Mariano Lampugnani. Location: Oxford
Bottom: Old Rhizomorphs (‘Boot-laces’) under the bark of a fallen tree

QUICK ID TABLE: HONEY FUNGUS Armillaria mellea

CAP / FLESH

3-14cm across. Initially rounded/domed. Expanding into variable shapes including shallowly domed, depressed centre and/or wavy margin.