When Rose Diseases Aren't

Rose Wilt was long thought to be a suspected viral disease caused by grafting scions onto imported root stocks from the U.K., Canada and Australia. The American Rose Society's Consulting Rosarian Manual still lists the symptoms as "downward leafroll, vein-clearing, premature abscission, [and] shoot proliferation from single buds."

In fact, these characteristics commonly occur in a variety of rose classes and may be indications of grafting one rose class onto the root stock of another class. They could just as easily be a deficiency or overabundance of specific minerals needed to produce healthy, "normal" roses.

The fact is, rose wilt, as described by the U.S. Department of Agriculture, does not exist. They have since declared themselves in error by repealing the import restrictions placed on roses grafted outside the United States.

Deficiencies and Excesses

To new rosarians, soil deficiencies may appear as a disease. The most common among these soil maladies is calcium deficiency which often manifests as brown, curling leaves at the top of the plant. Often the leaves shrivel and die.

A soil malady often mistaken as a viral disease is boron deficiency. This shows up as malformed, mottled yellow new leaves, appearing to grow excessively close to one another near the new-growth area at the shrub's top.

Still another, potassium deficiency, frequently fools the new rosarian. This soil malady appears as brown, scorched older leaves near the bottom of the plant, usually at the leaflet tips. The symptoms translocate up the rose until the entire shrub looks as if it has been systematically killed by a viral infection.

"Vein clearing," where veins appear lighter in color than the surrounding leaf tissue and mentioned as a symptom of the fictitious rose wilt above, is a symptom of excessive boron in the soil. But it is also a symptom of too little oxygen in the soil, and may mean soil drainage is inappropriate for good rose growing conditions.

Specific Replant Disease

Also called "sick soil syndrome," this malady manifests when roses are planted into soil previously occupied by another rose. The new rose appears to "sulk" for a year or two after planting. Growth is stunted and bloom production minimized regardless of how well the rose is cared for and how often the plant is fertilized.

There are two schools of thought regarding this "disease": some think it doesn't exist and some swear it does. Of those rosarians who believe it exists, the "camp" is further divided into those who believe the problem is an alleopathic chemical [1] exuded by the previously planted rose, and those who believe the soil is deficient in microorganic activity normally present to assist in plant development (micorrhizal fungi [2], for example).