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Identifying Problems With Roses

By Edited Nov 13, 2013 0 0

Some Problems That Can Be Faced When Growing Roses

Roses are favourites with almost all gardeners. There is a rose for every situation. There are now varieties that will act as ground-covers, climbers, and/or standards. Roses are tough and will bloom for months. If neglected, they still seem to survive and will continue to flower from year to year. It is no wonder that they are loved the world over. Great favourites are the David Austin roses, sometimes called 'English roses', which are the result of specific crossings of floribunda, modern hybrid tea and old roses. Roses of this type are very fragrant and have a wide range of colours and a long flowering season. The delicate charm of the older type roses has been retained but given a new lease of life with an enhanced colour palette.

A perfect specimen

Like all flowers, roses do have their problems from time to time. Some of these problems are listed below.

If foliage becomes brown round the edges and looks cracked and dry, the bush has possibly been sunburnt. Water droplets collect on the ends of the leaves and these can magnify the sun's rays on extremely hot days. It is ideal to water under the bushes but certainly water early in the morning or when it cools of in the evening. In hot weather, try to give the bushes a slow, deep soaking.

Mulching will also help conserve moisture and will keep the root system cool. As long as mulch is well aged and has a neutral pH, there are a number of different types of mulch which can be used. Pea or bean straw, seaweed, compost from mushroom farms, autumn leaves, stable straw and lucerne hay are all suitable. If you use wood chips or wood shavings, add blood and bone or animal fertiliser to the mix. This is because as the wood breaks down it will deplete nitrogen from the soil.>

If the leaf edges have a shiny, white appearance with brown split or cracked edges, there may be salt deposits in the water. This problem is most prevalent in late summer when bore water or poor quality water is used. Salt deposits can come from overhead watering or from water drawn up through the soil by the roots. To prevent salt deposits forming on the leaves, water deeply and don't water overhead.

Rose infected with black spot

Blackspot (above)

Fungal problems such as powdery mildew and blackspot thrive during periods of warm days and cool nights in spring and autumn. These diseases are particularly troublesome if you water from overhead. Powdery mildew causes a white powdery effect on buds and leaves while blackspot shows as black spots on older leaves. The leaves then turn yellow and drop off. Water from under the bushes and treat with a fungicide. Once summer comes with warmer weather, the plants will recover.

Dry-looking leaves which drop off easily may have mites on the underside of the leaves. The flowers may look dead. You may need a magnifying glass to see the mites. Wet the foliage several times a day to increase the humidity. Mulch and wet the surrounding soil. Mites are difficult to control as they become immune to sprays. Dusting with sulphur may help. Potted roses and plants in dry, dusty situations along paths, driveways and patio areas are susceptible to infestation by mites.

Young leaves and new growth that appear yellow but with green veins may indicate a lime-induced chlorosis due to limestone or highly alkaline soil. The iron in the soil is locked up and unavailable to the plant. Agricultural sulphur can be used to lower the pH of the soil. Iron chelate mixed with compost will help as will fertilisers with a higher sulphur content. These would be preferable to animal manures. Check the labelling of the fertilisers to find one which has a relatively high sulphur content.

Damaged and/or distorted buds result from a bad mildew attack or damage from aphids early in the developmental stage of the bud. Spray mildew with a fungicide. Use the jet nozzle on your hose to get rid of the aphids or use an insecticide. Throwing soapy water over the plant will also help get rid of aphids. Buds that look as though they have been chewed or have a hole through them are probably being attacked by garden weevils. Look for them at night. Spray with carbaryl. Looper caterpillars are small and white to green in colour. They hide in folded leaves and can be sprayed with an insecticide.

Rose leaf infected with rust

A leaf infected with rust (above)

Rust causes distortion of the buds and loss of flowers in summer. It appears as a scattering of orange-brown spots on the undersurface of leaves. Prune away and burn infected wood and leaves. Fresh outbreaks can be combatted by spraying the bush and surrounding soil with a commercial preparation. Check rose bushes for rust in early spring as the disease is dormant in the winter and springs to life in warmer weather. Once rust is established it will take devoted and dedicated action to get rid of it.

Roses that are not thriving could be infested with mites. Another reason for ill-thrift could be that they are not getting enough water. Slow soaking for an hour or two is better than watering for short periods every day. Another reason for roses failing to thrive is soil which repels water. If the soil is sandy, use a wetting agent to improve absorption of water. Clay soils need an application of gypsum then a wetting agent.


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