12 garden diseases and disorders – and how to fight back

Garden problems and how to tackle them

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Even the most manicured of gardens can be beset by disease and disorders. Many of these problems can be cured, but in most cases prevention is the best way forward. Here are some common problems and how you can help keep them from getting through the gate.

Rose black spot: symptoms

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A disease is an infection by a micro-organism, either a fungus, a bacteria or a virus. Characterised by yellow discolouration with brown and purple spotting on leaves which eventually causes them to drop. The disease spreads easily from infected areas especially during wet weather and greatly reduces the plants vigour. The fungus is carried on wind-blown rain so expect recurrences and be vigilant at the first signs of illness.

Rose black spot: treatment

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Hygiene is the order of the day. Cut off or pick up any infected leaves, remove any stems with lesions and dispose of them. Keep your tools clean to risk contamination. Fungicide sprays, both organic and chemical, are also available and you’ll need to follow the instructions carefully and repeat applications. Alternatively, a cheap home remedy such as a baking soda in water can be used, which also works on powdery mildew, making it a great 2-in-1 solution.

Damping off: symptoms

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Maybe you're trying to plant up a new garden by growing from seed and you notices the new shoots are not doing so well. A fungal disease that attacks seedlings especially if over-crowded, over-watered and in a badly ventilated environment. It can destroy an entire newly-seeded plant rapidly and the young plants collapse at the base and die. Meanwhile the fungal spores rest in the soil ready to strike again.

Damping off: treatment

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Ensure that all pots and tools are thoroughly cleaned so any resting spores are killed. Make sure to use fresh compost and sow seeds thinly. Lastly, place your pots or trays where there is good air flow and don’t over water them. READ MORE: Just moved? Top tips for your new garden

Box blight: symptoms

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An epidemic that has seen gardeners shun the box hedge in favour of more robust alternatives. This disease can be identified by the yellow and brown discolouration of the evergreen leaves, because parts of the plant dies revealing dead and bare stems. It spreads easily and although it doesn’t kill the roots, areas affected don’t tend to recover well.

Box blight: treatment

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Cut out any dead or diseased areas, collect up the leaf litter and burn it all. Ensure any tools used are disinfected, including any footwear worn near infected plants. Fungicides are available with varying results. Never water from above but aim directly for the soil underneath the shrub as wet conditions increase the spread of the disease. As a preventative measure think about quarantining new box plants before allowing into your garden.

Honey fungus: symptoms

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A titan of a disease, surviving in the soil for up to 30 years and insidiously spreading underground by a metre every 12 months to infect and kill the roots of trees and shrubs. Symptoms include a white fungus underneath the bark which eventually turns to black ‘bootlaces’ and honey-coloured toadstools around the base of the trunk.

Honey fungus: treatment

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The only method of control is to remove and burn all infected material and regularly excavate the soil to limit the spread of the fungal disease. A vertical rubber barrier can be deeply buried into the soil to help prevent further spreading or to protect susceptible plants. In addition, look for plants that are listed as being less vulnerable to this enemy.

Powdery mildew: symptoms

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A fungus that grows on leaves, stems or flowers and is clearly visible as a grey/white powder. It stunts growth and the spores spread to infect neighbouring plants. It can impact a wide range of plants and is prevalent from spring onwards.

Powdery mildew: treatment

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As it is a fungus that exists on the surface it can be treated. Prune out and clear away all of the infected plant. Mulching your plant (the process of covering the soil with organic material such as bark) and watering it can provide conditions less desirable to the disease. Fungicide sprays are available and are very effective, just be sure to use a suitable product especially if the plant is being grown to be eaten.

Potato and tomato blight: symptoms

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This disease strikes fear into the heart of anyone trying to grow their own veg. Affecting crops mostly in wet weather when spores can spread, it infects the foliage and causes fruit to rot. The leaves also wither and go brown. This can occur from early summer onwards and unfortunately once an infection takes hold there’s no turning back.

Potato and tomato blight: treatment

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Once again hygiene is important, collect and dispose of all infected material. With potatoes, earthing up can provide some protection and early harvested varieties have more chance of escaping the disease. Tomatoes are at a lower risk if grown in a green house. Practice crop rotation to minimise the risk of infection again next year – don’t give up, try again!

Drought: symptoms

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A disorder is when the plant is detrimentally affected by something that is not living. We have all experienced harsh drought conditions this summer; parched lawns, cracked earth, plants wilting and dying, crops failing and ponds drying up. Water is essential for our gardens and for healthy plant growth. It's a scary thought to think: what if this weather change is here to stay?

Drought: treatment

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Simply put the solution to drought is watering! If a pot is particularly affected sit it in a bucket of water to drench the soil. It is better to deeply water once a week than a little every day. Consider saving water by installing a water butt or trough. Recycle water from your house, often called grey water (i.e. used bath water) to use on the garden. Choose more drought resist plants such as Lavender, Rosemary, Sedum, Geranium, Eryingium and Grasses too.

Fasciation: symptoms

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A rather wacky and harmless disorder that can create all sorts of freaks of nature. It is a disorder of the cells which causes the shoots and flowers of the plant to become misshapen.

Fasciation: treatment

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Fasciation doesn’t harm the plant and won’t necessarily reoccur. You can simply cut it out if it does not fit with your aesthetic or leave it in to enjoy the weird and wonderful world of nature.

Frost damage: symptoms

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Look out for blackened leaves and stems which are withered or collapsed. Frost damage can severely harm a plant to the point of killing it. However with some plants it may just be the extremities that are affected, once the damaged is removed and with an increase in temperature it may well recover. It all depends on the hardiness of the particular plant, the situation it is in and the weather conditions experienced.

Frost damage: treatment

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Tender plants should be given protection over winter. Either by placing them in a cold frame or greenhouse, porch or garage. With more hardy plants which may still be susceptible, a horticultural fleece can be wrapped around them to provide protection. Mulches around the base of plants can also help. Keep an eye on the weather, especially during early spring, and if a particularly cold spell is due – rush out and cover them up!

Waterlogging: symptoms

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Plants need water to live but too much and they can literally drown. A plant needs oxygen at its roots and when excess water prevents this the plant suffocates. Characterised by wilting, yellowing leaves, stunted growth and roots which turn black and smell rotten. It can be caused by weather, garden position, poorly draining soil, or by overzealous watering habits.

Waterlogging: treatment

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Make sure your soil has adequate drainage, consider adding grit, sand or perlite to improve aeration. With pots add crocks or large stones to the bottom off the pot and use pot feet so the water can flow away. If your garden is prone to flooding consider installing soakaway drains, altering the gradient of the plot or using raised beds. Certain plants love having wet feet so do your research and find the water lovers.

Shade: symptoms

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Whether you're put your greenery in the wrong spot indoors or it's struggling in the garden, too much or too little light is never good. Plants that are struggling in the shade will exhibit either stunted growth or leggy growth towards the light, as well as, failed or reduced flowering and a loss of foliage colour.

Shade: treatment

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Consider the canopy above the area and the option to cut back surrounding trees or shrubs which are creating the shade. This really is a case of using the right plant for the right place. Many plants thrive in shade, from Ferns to Hostas, Astilbes to Foxgloves, there’s a myriad of plants to choose from. Embrace your dark side!

Rose balling: symptoms

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The buds don’t open but are fused together in to a papery ball which turns brown and then slimy. In some cases this can then be attacked by mould. It is caused by wet conditions where the flower fails to dry enough to open and the outer petals form a tight case from which it can’t break through.

Rose balling: treatment

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This disorder isn’t severe and can be easily remedied by taking action. Cut off all the damaged buds until all that is left is a healthy shoot. This prevents mould from taking hold and causing further problems for the rose.

Hungry for more great garden advice? Check out these 13 common garden pests and how to treat them.