Honey fungus

Armillaria mellea and other Armillaria spp.

also called Armillaria, Bootlace fungus

A fatal root disease of woody plants: white fungal sheets under the bark and honey-colored toadstools at the base. Remove the plant with as much root and stump as possible.

Fungus No cure Soil-borneSpread by contact Spreads to neighbors

What you'll see

Peel back the bark at the base and there are creamy-white fan-shaped sheets of fungus, smelling strongly of mushroom.
Flat black bootlaces, like thin bicycle cable, run through the soil and over the roots.
Honey-colored toadstools with a ring on the stem appear in clumps at the base in autumn, then vanish after frost.
The plant declines suddenly — leaves small and pale, an unusually heavy flowering or fruiting, then death of one limb or the whole crown.
Bark at the collar cracks and may bleed a dark gum or resin.

Why it happens

A soil-borne fungus that lives on dead stumps and roots and spreads from them through the ground by black rhizomorphs, the bootlaces, which invade the roots and collar of living woody plants. Buried timber, old stumps and long-dead hedge roots are the reservoir. Stressed, drought-hit or newly planted trees are taken first.

It is a permanent feature of ground with old stumps and buried wood rather than a weather event. Drought, waterlogging, root damage from building work and poor planting all make a plant far more likely to succumb.

Treating it

There is no chemical control available to gardeners and no cure for an infected plant.
Dig out the whole plant with as much of the root system and stump as you can physically get, and burn or take away the material.
Grub out any old stumps and buried timber in the surrounding ground at the same time.
A vertical barrier of thick butyl pond liner, sunk 45 cm and standing 3 cm proud, will slow the bootlaces spreading into a valued area.
Replant only with resistant subjects — yew, box, hornbeam, beech, bamboo — or grow herbaceous plants and vegetables there instead.

Keeping it away

Never bury woody waste, and remove stumps rather than leaving them to rot in the ground.
Keep trees and shrubs vigorous with mulch and water in drought; healthy plants resist far longer.
Avoid damaging roots and collars with mowers, strimmers and trenching.
Plant at the correct depth, and do not pile mulch or soil against the trunk.
Choose resistant species when replanting near a known outbreak.

Who gets it

Almost all woody plants; privet, lilac, rose, apple, birch and Leyland cypress are notably susceptible, while yew, box and beech resist it well.

and 9 more in the catalog