Fertilizer to Make Rose Leaves Thicker & Greener in Zone 9B

Types of Fertilizer

• Fertilizers may be either inorganic or organic and come in liquid or dry, quick or slow-release forms. Slow-release fertilizer is recommended by the College of Agriculture at the University of Arizona. A balanced rose fertilizer, according to the American Rose Society, is one that uses a 6-12-6 mixture (6 percent nitrogen, 12 percent phosphorous and 6 percent potassium). This is considered ideal for the country in general, but adjustments need to be made for zone 9B. Specifically, more nitrogen is often needed.

Symbiosis Between Fertilizer and Soil

• The amount of fertilizer needed depends upon soil pH (potential Hydrogen ions). For healthy roses and rose leaves, aim for a pH level of 6.0-6.5. Much of the soil west of the Mississippi River is alkaline. Adding rock sulpher or organic materials will lower pH levels. The horticultural department at Texas A&M University recommends a sulphur compound, fed twice-yearly to each individual rosebush, in areas with alkaline soil.

How and When to Feed

• With the right pH balance, the ARS suggests monthly feedings during the growing season. The University of Arizona recommends feedings every six to nine weeks, while New Mexico State University's website advises fertilization every four to six weeks. As you can see, there is no consensus as to the best schedule for rose-feeding. The nearer your soil is to the ideal pH of 6.0, the more closely you will follow the ARS recommendation.

Specific Problems

• Nitrogen deficiency is found throughout much of zone 9B. According to the Agricultural Department at the University of California, it may precipitate leaf drop. Nitrogen supplements are added as inorganic fertilizer or, if preferred, as organic material such as compost.

  Chlorosis, which might indicate a lack of iron, zinc or other minerals, is marked by a yellowing of leaves. Iron and zinc may be added directly to the soil or sprayed on the foliage. The latter method is preferred by the horticultural department at Texas A&M.

Other Considerations

• Although roses require ample fertilization, avoid excessive feedings. Some nutrients, such as boron, are toxic in high amounts. Texas A&M cautions against the use of fresh straw or hay, which can leech nitrogen from the soil. Well-composted mulch is recommended. Texas A&M also advises against the use of chemical feeds late in the season, when only organic types should be applied.

  A rose is a rose only when thick, deep-green leaves add to its stunning beauty. If these guidelines are followed, healthy, bountiful leaves are likely.