The Yellow Leaves of Roses (Nutritional Deficiencies) Part 2

By Ed Bradley

In another article, I described the yellowing of leaves, caused by disease, insects/mites, too little or too much water, and physical damage. This article will look at the yellowing of rose leaves caused by nutritional deficiencies.

Remember that roses are heavy feeders. Healthy rose bushes produce an enormous amount of growth over the course of our 8 to 9 month growing season. As they bloom, we remove long stems, and they produce 2 or 3 more in their place. The removal and re-growth process occurs throughout the growing season. And, at the end, it is not unusual to have a bush 6 or 7 feet tall and 3 to 4 feet wide. And, when you realize that you have removed at least that much growth during the season, it is no wonder that they consume a huge amount of rose food.

Roses require a good, balanced fertilizer. That is, an ample amount of the major elements – Nitrogen (N), Phosphorous (P), and Potash (K), plus an available supply of the 17 trace elements. Deficiencies of N-P-K become readily apparent in the color and vigor of the bush. A deficiency in any of the trace elements may not be as immediately conspicuous, but will show up over time by discolored, distorted, dead or dying leaves.

A good soil mix, with plenty of organic material, normally contains an adequate amount of the trace elements. They are called “trace” or minor elements because only a very small amount is needed for normal plant growth. However, most quality fertilizer producers recognize the need for these trace elements, and the better fertilizers generally include a sufficient amount to sustain healthy growth. “Trace” elements are sort of like vitamins in our diet. Eating normally healthy foods generally gives us enough of the vitamins needed; however, if we have a special condition or as we grow older, it may be necessary to supplement our diet with certain vitamins. So it is with “trace” elements for plants.

Most cases of trace element deficiency are caused by some interference in the availability or uptake of these elements from the soil, rather than by an actual shortage of these nutrients in the soil. Poor aeration, over watering, root-knot nematodes, high levels of soluble salts, excessively high or low soil temperatures, and high or low pH may cause the trace elements to be unavailable to the plant.

Having said that, however, we all see spotted leaves, yellowing leaves, brown leaves and dropping leaves – and wonder “What’s going on in the garden?” So, let’s take a look at some of the common deficiencies and symptoms.

First, the N-P-K deficiencies:

Nitrogen: leaves show an overall yellow-green color, with random leaf spots. Older leaves may turn yellow and drop off. Flowers of darker varieties may appear several shades lighter than normal.

Phosphorous: stunting of leaves and stem growth, followed by older leaves losing their luster. They may become a gray-green and drop off without turning yellow. Some may show dark red or purple colors. Petals of pink flowers may become dark pink.

Potassium: stunted growth, shorter flower stems; small, short, deformed flower buds. Browning and dead tissue mainly at edges of leaves.

Now, let’s look at the trace element deficiencies:

Iron: areas between the veins of young leaves turn yellow, but veins remain a light green. There is generally an adequate amount of iron in the soil; however, because of the normally high pH of our soil, the iron is rendered unavailable. Therefore, the need to periodically add iron to our feeding program.

Calcium: young leaves are distorted, hooked or curled. Older leaves become a dull gray-green and may bend down at the edges. Later the edges may turn yellow, then brown with discolored blotches.

Boron: young leaves are light green at base, and twisted.

Copper: young leaves are permanently wilted with no chlorosis (yellowing).

Magnesium: yellowing starts from center of leaf, with signs of dying tissue.

Sulfur: leaves are light green with lighter green veins.

Zinc: large areas of dead tissue at tips and between veins.

Remedies can be very specific, such as Sprint 330 for iron or Epsom Salts for magnesium; however, a good application of a balanced fertilizer with trace elements will cure most unhealthy leaf problems caused by nutritional deficiencies. Lightly stir the soil for aeration, and add a good compost mulch to enhance the effectiveness of the fertilizer.