You will hear all types of theories and philosophies on how to fertilize roses. This is a plant that has a lot of very devoted amateur growers and each one will have their own little secrets. However, remember that, just like every other plant in the world, roses require a certain basic level of nutrients in order to grow and flower properly.

So, submit a soil test periodically to determine the level of nutrients in your beds. Reputable soil labs such as those at your land grant university will have research based recommendations for the type and amount of nutrients needed to keep your roses (and you) happy.

In the absence of a soil test, you can make two or three applications of a balanced i.e. 12-12-12, fertilizer during the growing season. An equivalent amount of nutrients could also be applied using an organic source such as a composted manure product.

Generally, the roses will need fertilizer when the new growth appears in the spring, again about 6 weeks later and a final application about 6 weeks later. In temperate zones, you should stop fertilizer applications around early to mid-August. Fertilizers, especially nitrogen, applied later will trigger new, lush green growth that may not have time to harden off before the first frost.

Keep an eye on the plants and, as long as the leaves are dark green and the flowers are being produced, everything should be just fine. If the leaves are yellowing, check to determine the cause. It could be an alkaline pH, aphids, virus or droughty conditions. If those are not present, then it is probably caused by lack of nitrogen. Another possibility is low magnesium which is a part of the green chlorophyll molecule. People sometimes apply epsom salts which contain magnesium to overcome this problem.

Again, have your soil tested and it should help you answer all your fertilizer need questions.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 
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