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Loamy clay soil with a clay content of 15-25 percent is ideal for growing roses. It is fertile and absorbs and retains moisture well, while remaining porous enough to allow good aeration of the soil. Other soil types, such as clay and sandy soil will need work done to it to successfully grow roses. The pH level and the drainage of the soil should also be tested, and rose sick soil will need to be treated or replaced.

Any soil with a clay content higher than 30 percent will be unsuitable for roses unless its structure is modified. Clay soil can be improved by adding coarse river sand, organic material (well matured stable manure combined with bedding straw is ideal), while gypsum and magnesium sulphate will help improve soil structure.

To improve structure of clay soil do the following:

1. Take out the topsoil down to a depth of 40cm and put to one side, and the subsoil down another 30-40cm to the other side.

2. To each pile mix 2 parts clay soil, 1 part coarse river sand and 1 part organic material. To this add 3kg of gypsum per cubic metre.

3. Return the subsoil. Before returning the topsoil, if necessary, add ingredients to adjust pH level (see pH instructions below), and return topsoil.

Sandy soil is comprised of 3-10 percent clay and 85 percent or more sand. Sandy soil dries out more quickly than clay and nutrients leach out faster. To help with sandy soil dig deeply to a depth of 80cm and add lots of organic material such as compost, finely milled bark and well matured manure. This will not only enrich the soil but assist moisture retention and enable roots to spread. The addition of wood shavings or clinker ash will help make the soil more friable and less likely to become compacted.

It is important to test the pH level of your soil. Roses prefer a fairly acidic soil with a pH between 5 and 6.5, but they can also grow in soil with a pH up to 7.5. You can test the soil yourself by buying a soil testing kit from a nursery or you could have a few samples from different parts of your garden tested in a laboratory.

An acidic soil with a pH level less than 4 can be harmful to plants. To reduce acidity levels apply agricultural lime or dolamite to soil with a pH level less than 4.5. Professional guidance should be sought for this as too much lime will raise the pH to undesirable levels.

Alkaline soils can be acidified by sprinkling 15g of ammonium sulphate or 10g of urea around each plant, or 60g of magnesium sulphate can be applied to every square metre of soil. Whichever method you use, the substance used to increase the acidity of the soil should be watered in well in order to avoid burning the rose bushes.

Roses need adequate drainage. To establish the adequacy of drainage dig a few holes 60cm deep, fill these with water and watch to see how long it takes to drain away. If it remains in the holes much longer than half an hour then you may have a drainage problem. Provided the bed has a slope of at least 2cm per metre and there is an outlet for water, a simple system of furrows and plastic drainage pipes would be enough to solve the problem. Another way of solving the problem would be to raise the bed 30-50cm above the surrounding area, containing it by means of a low wall.

Rose sick soil is soil in which roses have grown for more than four years. While the affected soil will continue to support existing roses, new plants will not grow well. One way of overcoming the problem is to remove all the soil from the infected area and replace it with soil from elsewhere in the garden where roses have not grown before. All other plants will grow in the rose sick soil without any trouble. If a large area is involved, it might be advisable to call in a specialist to sterilise the soil.