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There are many reasons that the leaves on your roses turn yellow. Roses are deciduous plants that lose their leaves as they go into dormancy over the winter months.
However, if the leaves of your roses are turning yellow and it is not the right season for this to be happening, there could be a number of problems.
Rose leaves turn yellow due to water stress (either getting too much or too little), heat stress, nutrient deficiencies (most often nitrogen, iron, or magnesium), insufficient sunlight, incorrect use of fertilizer, or pests and diseases like black spot, rose leafhoppers or spider mites.
To give our roses the care they need, we must learn how to diagnose their troubles. This article discusses how to determine the reason behind your roses’ leaves turning yellow and what to do to resolve the problem.
1 – Fertilizer Burn Causes Rose Leaves to Turn Yellow
If liquid fertilizer is not diluted according to the instructions on the label, or too much fertilizer is applied to roses, it causes fertilizer burn. The leaves turn yellow and dry out.
Fertilizer burn happens when there are excess nutrients, like nitrogen, in the soil – too much for the plants to take up. The excess nutrients accumulate in the soil as mineral salts, and they draw moisture from the soil.
It is critical to fertilize your roses moderately. Always dilute a little more than what the label states to prevent any mishaps.
To be on the safe side, choose organic fertilizers that feed the soil, such as compost, leaf mold, and bone meal.
To help roses that have fertilizer burn, prune off the yellow foliage and water the plant thoroughly for a few weeks. This will help leach the nutrients out of the soil.
Investigate if there could potentially be fertilizer runoff from a sloping lawn. This is especially common after high rainfall events.
2 – Nitrogen Deficiency in Roses Cause Yellow Leaves
When roses cannot get the nutrients that they require from the soil, they become stressed. A common nutrient deficiency in roses, especially those growing in sandy, nutrient-poor soils, is nitrogen. It causes the leaves to turn yellow.
Soils that are high in sand and lower in organic matter do not hold onto water, so plants struggle to take up water-soluble nutrients, like nitrogen.
It is especially important to apply organic fertilizer, like compost, leaf mold, bone meal, worm castings, and well-rotted manure, to roses annually if you are growing them in sandy, nutrient-poor soils.
To help roses that have a nitrogen deficiency, feed them with a rose-specific fertilizer, water them well, and apply a 1-inch-thick layer of mulch around the base of the plant.
To keep roses thriving, it is good to do this annually during spring, as well as late in the fall, to insulate the soil from the frosty winter temperatures.
3 – Alkaline Soil Turns Roses’ Leaves Yellow
Another reason that roses’ leaves turn yellow is due to alkalinity in the soil, which causes a deficiency of iron. A tell-tale sign of an iron deficiency is yellowing of the leaf veins specifically.
The ideal soil pH for roses is neutral to slightly acidic (pH 6-7). If your garden’s soil is too alkaline, meaning the pH is too low, roses will struggle to take up certain nutrients, like iron.
Likewise if the pH of the soil is too high, above 8.5, roses will struggle. This can sometimes happen if they are overwatered.
To test the pH, use a soil gauge. They are cheap, readily available online, and simple to use. Alternatively, if you have a neighbor that gardens, ask them what the soil pH in your area is.
If the soil in your garden is not suitable for growing roses, worry not! You can plant your roses in pots so that you have complete control over the soil conditions.
4 – Magnesium Deficiency Leads to Yellow Leaves in Roses
Rose leaves can also turn yellow due to a deficiency of magnesium. This is caused by similar soil conditions that cause iron deficiency.
It is simple to resolve this issue: apply a quarter cup of Epsom salts around your roses and water them thoroughly.
5 – Yellow Rose Leaves from Water Stress
Roses are generally drought hardy, but long periods of dry soil and baking heat will have them showing signs of water stress. Their leaves turn yellow and dry out.
How much and how often you water your roses depends on the climate that you garden in, but typically roses should be watered generously once a week.
If you grow your roses in raised beds or pots, you need to water them more frequently, as containers lose water more quickly.
To revive a drought-stressed rose, water it generously and apply a 1-inch-thick layer of mulch. Use a mixture of compost, leaf mold, and bark chips. Water them consistently every week.
6 – Overwatering Turns Roses’ Leaves Yellow
On the contrary, too much water is also not a good thing for roses. Roses require soil with good drainage because they do not enjoy having wet feet.
When excess water does not drain away, and the soil remains saturated, the roses’ roots are starved of oxygen. This stresses them, causing the leaves to turn yellow.
The problem may be that you are watering the roses too frequently. It could also be that the soil contains too much clay, and water cannot drain easily.
To ensure you do not overwater your roses, check the soil moisture before you water them. Insert your finger a few inches and feel how wet the soil is. If you feel some moisture, you can wait a day or two before you water your rose.
A slightly more reliable way to test soil moisture is using a moisture meter. These are cheap and available online or from a garden supply store. You will feel 100% confident that you are not overwatering your roses!
To amend soils with poor drainage, add lots of compost and other organic matter. This will improve the soil structure, making it more aerated and friable, which allows water to drain through it more easily.
7 – Heat Stress Causes Rose Leaves to Turn Yellow
Roses thrive in full sun, but sometimes the baking sun can get a little too hot for them. When the sun shines directly onto bare soil, heat is reflected back upwards. It is this heat that singes roses’ lower leaves, causing them to turn yellow and drop.
It is critical to apply a thick layer of mulch around your roses, covering the soil completely. This will retain moisture and help keep the roots cooler in summer.
Dark surfaces radiate more heat than lighter-colored surfaces, so if you live in a region with scorching summers, use a light-colored mulch, such as cedar chips, instead of darker mulches.
Heat stress in roses is exacerbated by overwatering. If a puddle of water remains around the rose plant after you water it, the reflection of the sunlight off the water will severely burn the roses’ lower leaves.
8 – Roses Do Not Like Too Much Shade
If roses do not get enough sunlight, their leaves turn yellow and fall off. They require a minimum of 6 hours of sun per day to grow and flower successfully. Avoid planting roses in partial or deep shade.
For potted roses, this problem is easy to fix – just move the pot. However, if your rose in the border has become shaded by the growth of a tree limb, you will either need to cut the branch back or transplant the rose to a more suitable area.
Roses do not even tolerate the shade of their own foliage. It is common to see the lower leaves on rose bushes turning yellow and dropping. This is normal and a sign that the plant is keeping itself healthy.
To help a rose bush that is suffering from a lack of light, prune away yellow foliage, and address the lighting issue either by moving the plant to a sunny spot or getting rid of whatever is blocking the sunlight.
9 – Roses Drop Their Leaves in Winter
Roses are deciduous plants. It is part of their natural life cycle to lose their leaves and enter a state of dormancy over winter.
If your rose bushes suddenly start turning yellow and dropping their leaves in the fall, do not panic! This is totally normal. They will grow back in spring.
10 – Black Spot Turns Rose Leaves Yellow
Black spot is a fungal disease that roses are susceptible to in the spring. Microscopic fungal spores float on wind currents and invade your garden from above.
Modern roses are bred to be resistant to it, but the fungus strains mutate quickly and overcome the plants’ defenses. Roses most susceptible to black spot are climbers, floribundas, and hybrid tea varieties.
The symptoms of black spot are purple or black patches on roses’ leaves that spread. The leaves turn yellow and drop off. On young stems, you may see dark, scabby lesions. If black spot goes untreated, a rose can lose all its leaves, taking a serious knock to its growth.
To control the spread of black spot, one must prune off stems with lesions, collect up all the contaminated leaves and stems, and dispose of them in a sealed black bag. Use a sterile pair of pruning shears and disinfect them again with alcohol after each cut.
Black spot spores can spread incredibly easily, so every precaution must be taken to prevent the disease from being spread to healthy growth.
Apply a fungicide that is specifically for rose black spot. Be careful not to spill any fungicide on the soil when you apply it as it is extremely detrimental to soil health.
11 – Spider Mites Cause Yellow Rose Leaves
Spider mites are tiny sap-sucking pests that sit on the undersides of rose leaves. They damage roses because they suck chlorophyll-rich juices out of the leaves, turning them yellow. Identify spider mites by the webs they build on the underside of leaves.
One of he underlying reasons spider mite infestations are such a widespread problem is the use of broad-spectrum insecticides containing carbaryl.
This type of insecticide kills all invertebrates, including the spider mites’ natural predators. This only makes the spider mite problem worse in the long term.
To control spider mites on roses, one should use an insecticidal soap. Spray it onto the entire plant in the morning or in the evening, never in the middle of the day.
Insecticidal or horticultural soaps are made from plant oils. They stick to soft-bodied pests, like spider mites, aphids, and mealybugs, and suffocate them
You will need to reapply the treatment weekly until you do not see anymore spider mites on your roses.
12 – Yellow Leaves Due to Rose Leafhoppers
Leafhoppers are destructive little pests. They are between 3 and 15mm in size, with a large set of wings. Most often, they are green in color but they come in a range of colors.
They feed on plant sap, similar to spider mites, and cause roses’ leaves to turn yellow with small white spots. Leafhoppers can also transmit bacteria, such as leaf scorch, between plants.
Treat them in the same way you would spider mites. Monitor their population and keep applying the insecticidal soap weekly.
Plant companion plants amongst your roses, as these will help to deter some of the pests. Garlic chives are great for keeping leafhoppers, aphids, and spider mites away.
Roses’ leaves turn yellow for several reasons – nutrient deficiency, pests or disease, heat stress, lack of light, too much, or too little water. We need to consider all these reasons and narrow them down, by process of elimination, to figure out why our roses’ leaves are turning yellow.
There is a solution to every problem, and as you become more experienced as a rose grower, you will learn to identify and address issues more easily.