Diseases & Disorders

Helpful advice on what to do when problems strike, whether they're diseases, disorders or otherwise - and how to prevent them occurring


Fungal infection

Phytophthora is our second most reported disease. Causing die-back and leaf damage on trees and shrubs and is often fatal.

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  • Hellebore black death

    Hellebore black death

    Hellebore black death is a serious disease of hellebores, probably caused by the virus Helleborus net necrosis virus (HeNNV), where plants become stunted, deformed and marked by black streaks and ring patterns.

  • Hellebore leaf spot. Image: RHS/Tim Sandall

    Hellebore leaf spot

    Hellebore leaf spot is a common fungal disease of many hellebore species. It infects leaves and stems giving rise to roundish, dead, brown spots.

  • ©RHS WSYD0016025

    Herb robert

    Herb robert (Geranium robertianum) has small crane’s-bill pink flowers and pungent foliage. It grows commonly in shaded areas where it can be a useful ground cover but its tendency to selfseed can make it a nuisance as a garden weed.

  • Heuchera rust

    Heuchera rust

    Until recently, Heuchera could be considered relatively trouble-free in terms of foliar diseases. However, Heuchera rust is becoming an increasing problem, affecting both the aesthetic quality and the vigour of affected plants.

  • Holly blight in hedges causes 'arches' of defoliation. Image: RHS, Horticultural Science

    Holly leaf blight

    Holly leaf blight is a disease that causes leaf fall and twig die-back in several holly species.

  • Honey fungus. Image: RHS, Horticultural Science

    Honey fungus

    Honey fungus is the common name given to several different species of fungi (Armillaria) that attack and kill the roots of many woody and perennial plants. The most characteristic symptom of honey fungus is white fungal growth between the bark and wood usually at ground level. Clumps of honey coloured toadstools sometimes appear briefly on infected stumps in autumn.

  • ©RHS_scn0005448

    Honey fungus: making a spore print

    Mushrooms and toadstools change as they age, so it can be difficult to identify them. Honey fungus can kill garden plants. Here’s how to check if a mushroom is likely to be honey fungus.

  • ©RHS_SCN0004783

    Honey fungus: managing outbreaks

    Honey fungus infection can be deadly for plants. If it’s present in your garden soil there are several options you can use to control the disease and prevent future infections from emerging.

  • Horse chestnut bleeding canker. Image: RHS, Horticultural Science

    Horse chestnut bleeding canker

    Horse chestnut bleeding canker is a disease of the bark of horse chestnut. It causes cankers (bark infections) which bleed a dark or reddish brown sticky fluid.

  • Horse chestnut leaf blotch. Image: RHS, Horticultural Science

    Horse chestnut leaf blotch

    Horse chestnut leaf blotch is an unsightly, but not seriously damaging, disease of white- and red-flowered horse chestnuts. It causes irregular brown blotches on leaves.

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