Poor nutrition, excessive thirst or watering, and extreme weather conditions can all play havoc with your plants’ health.
Every rose plant should receive at least 20L water each week. But remember that roses need to be weaned off water after days of rain before resuming the normal watering cycle.
Heat stress is evident when brown blotches appear in the center of the leaves. Keep an eye on potted roses for these symptoms and water them well. Prevent the problem with a thick layer of mulch.
Iron deficiency is evident when the veins of the leaf remain dark green, but the rest of the leaf starts to yellow. This indicates that the soil is packed too tightly around the root system, preventing the roots from absorbing iron but it can also be a sign that you are overwatering. Various causes might be a shortage of nitrogen (dark-green veins and pale yellow-green leaves), phosphate (leaves with dark-green edges and brown blotches in the center), or potassium (dark brown edges with green and yellow blotches in the center). Thoroughly loosen the soil around the roots, add compost and peanut shells, and feed the plant with a rose food containing all the essential elements, such as Phostrogen or Chemicult.
Lack of leaves indicates thirst; mulch and water are the solutions.
Once a year, add a tablespoon of Epsom salts (magnesium sulphate) to the soil around each rose bush.
Avoid using pesticides, herbicides and other poisons on windy days.
Scale is a symptom of an under-developed root system, which calls for transplanting potted roses into bigger containers, or for adding compost, peanut shells and even river sand to your beds.
Stem cancer may result from the bottom of the plant being sunburnt. Completely cut away the damaged area and give the plant a good layer of mulch. Late frost may occur in the sun heating the plant tissue too quickly. Spray the plant with one part lime sulphur to five parts water. The white residue will reflect the sun, keeping the plant cooler.
Spraying is quicker and more comfortable when you use an efficient garden spray pump. A 5-7 liter capacity spray pump is adequate for a garden of 100 roses or less, but beyond that, it makes sense to opt for the knapsack spray with the hand pump. Go for the best you can afford; it’s worth the savings in time, effort and efficiency. When diluting the spray mixture, half fill the tank with water and add the spray to the half-filled tank. Before spraying, shake the container to mix the shower with the water and also shake while spraying so that the shower doesn’t settle at the bottom. Avoid spraying when it’s windy or during the hottest part of the day. Don’t mix and store the diluted spray mixture because it loses its viability within half an hour. Finish the spray in the tank by using it on the plants rather than pouring the excess down the drain where it enters the water supply.