CONSULTATIONS ON ROSE CULTURE
From notes taken during programs on rose culture presented by rose authorities cited.
By Frances G. Ballentine
Soil Processes and pH
By Dr. Rubert Prevatt
Dr. Prevatt's discussions centered on answering these questions: What is pH? Why is pH so important? What do you know about pH?
He defined pH as acidity measured by concentration, with pH of 7.0 as neutral. pH is generally defined as a measure of the hydrogen (acid forming) ion activity of the soil and expresses the degree of acidity or alkalinity of the soil.
Dr. Prevatt emphasized the important role pH plays in making nitrogen and iron available to the plants. Lack of nitrogen will result in poor growth.
Roses prefer a slightly acid soil (6.0 - 6.8). When the soil is out of this range, the plants will not be able to use nitrogen -- even if it is there!
Dolomitic lime MUST be worked into the soil to become effective. Lime should be applied into the root zone and incorporated into the soil. He suggested use a spade to take out 3 slices of dirt around the perimeter of each rose bush and dropping the lime down to a depth of at least 6 inches. Scattering lime on the surface will do no good.
Organic/Chemical Feeding Formulas
By Howard Jones
Howard Jones operated a mushroom producing facility in Virginia for many years and discussed the processes used to grow mushrooms, of which mushroom compost is a byproduct. He extolled the virtues of combining both organic and chemical feedings into a fertilizing program for roses.
It was noted that Sara and Howard Jones won several classes at the National Rose Show. This would attest to the value of their recommended feeding programs, including mushroom compost.
Rose Questions and Answers
Dr. Tommy Cairns, International Exhibitor and ARS Vice President
Dr. Tommy invited the audience to ask questions about roses. What a great opportunity to hear a world class authority discuss rose growing problems with ordinary rose growers. Dr. Tommy's wit and wisdom were much appreciated by those attending.
Q. Why do some of the leaves on my rosebush curl up?
A. Leaves will curl upward on a rosebush during extremely hot weather, especially when the bushes are dehydrated and have a low starch content in their leaves. Leaves curling downward indicate a manganese deficiency.
Q. Why do my roses have balled centers?
A. Balled centers (vegetative centers) are generally caused by an overabundance of nitrogen. This is especially true with Double Delight and some of the Austins.
Q. Why are some canes on my roses yellow and dying?
A. You probably have a problem with a decaying root structure. It can be caused by root rot, nematodes, compacted soil. The best solution is to cut down on the watering, fertilize more, and remove the dying canes.
Q. Your comments on neem oil and foliar feeding please.
A. Neem oil is overrated as a protectant from fungus disease. Foliar feeding is not recommended because if the moisture dries fast, it will burn holes in the foliage. Fertilizers are taken up by the root system and not by the leaves.
Q. Should we be using Indicate 5 in our spray tanks?
A. It is O.K. if your water is alkaline. Some spray solutions have built-in buffering agents, so Indicate 5 is not needed. It is a good product if you need it.
Q. Please comment on the shelf life of Avid and on its storage.
A. Shelf life of Avid is 2-3 years. As to storage, I recommend that you move your refrigerator out of the kitchen and put it in the garage for your chemicals. Then buy yourself a new kitchen refrigerator! Your chemicals should be stored under refrigeration where even temperatures can be maintained year round. Extremely hot temperatures and extremely cold temperatures can break down all our rose chemical products.
Q. How often should the soil for potted roses be changed?
A. Change the soil for potted roses every 2-3 years.
Q. What is IPM and should we adopt its teachings?
A. Integrated Pest Management is a system of maintaining control over pests and diseases by the least toxic methods, be they natural, chemical or biological! Always select the least toxic method that will get the job done.
Originally published in The Charleston Rose -- November 1998.