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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  • Leek rust. Image: RHS, Horticultural Science

    Leek rust

    Leek rust is a common fungal disease of leeks, but also affects onions, garlic and chives. The fungus causes bright orange, raised spots (pustules) on leaves.

  • Downy mildew on lettuce. Image: RHS, Horticultural Science

    Lettuce downy mildew

    Downy mildew of lettuce is a disease caused by a fungus-like (Oomycete) organism, producing yellow patches and fuzzy white mould on leaves. These patches turn brown as the leaf tissue dies. It affects seedlings and mature plants.

  • Lupin anthracnose

    Lupin anthracnose

    The lupin is a stalwart of the cottage garden, available in a huge range of colour combinations. Unfortunately, it is susceptible to a fungal disease called lupin anthracnose, which in wet weather can cause severe dieback.

  • Adding compost to a raised bed

    Minimising health risks in the garden

    A common sense approach when out in the garden will help reduce potential risks posed by plants or diseases and ensure we continue to enjoy the health benefits of gardening.

  • Mint rust. Image: RHS, Horticultural Science

    Mint rust

    Mint rust is a common fungal disease of garden mint, but also affects marjoram and savory. The fungus causes dusty orange, yellow and black spots on leaves.

  • Moss in a lawn. Image: John Trentholm/RHS

    Moss on lawns

    Most gardeners have trouble at some stage with moss on lawns. This is unsightly and is often a result of poor growing conditions. By improving the health of the lawn, moss can be kept at bay.

  • Flower mutations - proliferation

    Mutations: flower proliferation

    One of many mutations or disorders that can affect plants, proliferation is when one or more buds form in an already open bloom. The reason for this is not fully understood but, usually, not all blooms are affected. It is sometimes seen in roses but, in repeat-flowering cultivars, subsequent blooms are usually free from the problem.

  • Mutations:plant

    Mutations: plant

    Plant mutations, known as sports, breaks, or chimeras, are naturally occurring genetic mutations that can change the appearance of the foliage, flowers, fruit or stems of any plant.

  • Mycorrhizal fungi

    Mycorrhizal fungi

    Mycorrhizas are fungal associations between plant roots and beneficial fungi. The fungi effectively extend the root area of plants and are extremely important to most wild plants, but less significant for garden plants where the use of fertilisers and cultivation disrupts and replaces these associations.

  • Narcissus basal rot. Image: RHS, Horticultural Science

    Narcissus basal rot

    Basal rot of Narcissus (daffodils) is a fungal infection which decays the base of the bulb, often during winter storage. If infected bulbs are planted, the resulting growth is yellow and may not flower.

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