Yellow leaves are quite a common problem with roses and there are a number of reasons why this happens. Some of the problems that cause yellow leaves can be quite simple to avoid if you:
We tend to think immediately of pest and disease problems or misuse of fertilisers, but sometimes the yellowing leaves can be caused by other factors such as water stress or mechanical damage.
Are your roses getting the right amount of water?
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Irrigation drip lines apply the right amount of water to produce healthy roses. |
With the ongoing drought and water restrictions, roses could be stressed through insufficient watering. You will notice the symptoms of drought quite quickly, with wilted leaves and stem tips, scorching of the leaf margins and young growth as well as the yellowing of the leaves. If this is the case you will need to increase the water applied to the plant and mulch around the plant, out to the drip line.
The other side to the water story is that too much rain or water from irrigation may waterlog the soil and therefore take up the air spaces in the soil. This is known as anaerobic soil. Drainage needs to be sound for good rose growth. A waterlogged situation will lead to yellow leaves as well as drooping older leaves, soft and brown stem centres and flower buds that do not completely open. If these are the symptoms that your roses are displaying, you will need to improve the drainage and reduce your water application.
Mulch keeps soil cool and moist
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Mulch and protected positioning will ensure your roses survive harsh summers. |
Heat stress during the summer months can also cause leaf yellowing. Roses that have been recently planted and have not established a strong root system are most susceptible to heat stress. Heat stress can be exacerbated by windy conditions that dry out the leaves and require accelerated transpiration to keep the plant cool. The root system has to be able to keep up the demand for water from the soil. You will also notice scorched leaf margins, wilting and your rose petals may have dark edges. Mulch is a very effective way of keeping the soil under the plant cool and moist. If you live in an area where you know hot conditions and drying winds will be a problem, carefully consider where you will locate your roses. A protected position will help with these climatic problems. You may also consider using anti-transpirants on the foliage.
Root systems - don't dig and weed
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For healthy roses, don't dig or weed around the root zone because it often causes damage. |
Damaged root systems can cause yellowing of leaves, because in effect the roots are then struggling to supply water to the upper parts of the plant. The symptoms will therefore look like heat or water stress. Digging or weeding around the root zone often causes damage, especially with new rose plants. Some rose root stocks, such as fortuniana, have quite shallow root systems, and are easy to damage. A good layer of mulch will help reduce the weed numbers and there should be no need to dig in fertilisers - they can be applied to the surface and watered in. If there is any need to dig around the rose plant, do so in the cooler weather if possible and make sure that you water the roots well until they have recovered.
Editor's note
Lessons to learn:
