Soil

Soil is the key to healthy and beautiful roses. Dig into your rose plot in several places to see what the soil it is like. Soil is seldom perfect. It may have too much clay, too much sand, tons of rocks, or any of a dozen different problems. pH is also important.
You should test your soil pH. pH kits are available at nurseries and over the internet. A good pH test kit is worth the expense because inexpensive ones are often inaccurate. Most roses grow well with a soil pH of 5.5 to 7, although a pH of 6.5 is ideal. pH is a measure of acid-base balance and uses a scale of 1 to 14. 1 is extremely acid; 7 is neutral; and 14 is extremely basic (alkaline). Few flowers will grow in a pH that is too acid or too alkaline.
A pH of 6.5 is the point where nitrogen, phosphorous, and potassium, plus trace minerals, are most easily available to your flowers. Arid regions tend to have alkaline soils and regions with heavy rainfall tend to have acidic soils.