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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  • 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.

  • Narcissus leaf scorch

    Narcissus leaf scorch

    As its name suggests, this fungal disease causes scorch-like symptoms to appear on the leaves. Symptoms start at the leaf tips, when they are sometimes mistaken for frost damage. Flowers can also be spoiled by the appearance of brown blotches.

  • Magnesium deficiency on a tomato. Credit:RHS/The Garden.

    Nutrient deficiencies

    If plants fail to thrive, despite adequate soil preparation, watering and mulching, it may be a sign of a nutrient deficiency. Fruit and vegetables are particularly vulnerable, as are containerised plants and those growing in very acid or alkaline soils. Yellow or reddish coloured leaves, stunted growth and poor flowering are all common symptoms of nitrogen, magnesium or potassium deficiency.

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