Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden.
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We all love roses; they not only brighten the garden but are given as a sign of affection and love, or they can even be part of one of the biggest days of your life. Roses are one of those flowers that gardeners always want to grow and find a space for.
How do you get rid of black spots on roses? Black spots on roses can be a nuisance for any gardener. Caused by a fungus known as Diplocarpon rosae, this disease spreads blackspot spores which can significantly weaken the rose plant and reduce its vigor. There are a few treatments to rid you of this issue, so check out this post to learn more.
Table of Contents
In this post, I will walk you through the possible options to get rid of black spots on roses so you can enjoy these beautiful flowers without risking your plants from the black spot. Well, read on to find out.
What is a black spot?
The black spot is a fungus called Diplocarpon rosae. The fungal spores spread it splashed up onto the lower leaves of roses. The spores are also airborne and typically start during early spring. If left untreated, this rose disease can seriously affect the health of your rose plants.
It does this by spreading. Initially, it will look like little black or dark brown spots around 15mm in diameter. This affects the lower leaves and will spread to the rest of the plant, including the stems, in worst-case scenarios. Badly affected plants will not look like small spots but large blotches as they join together.
Ways to get rid of black spots on roses
Many gardeners, more often than not, focus on treatment and forget to address the conditions for thriving black spot spores. While prevention tactics cannot eliminate the risk of black spots, they are your best defense to counter the issue. The preventative approach is more straightforward than curing.
Here is a list of some of the best ways to prevent black spots on your roses:
- Ensure the rose plant is properly watered
- Water roses first thing in the morning
- Observe proper spacing
- Do not plant roses under too much shade
- Prune your roses and clean up your garden
- Clean your pruners with alcohol
- Apply a thick layer of mulch
- Grow natural disease-resistant varieties of roses
We will look more in-depth into each of these as this article continues. I would love to draw your attention to the video below that will teach you everything else about roses. I would suggest that if you grow roses, this video would greatly help you. Just click the video to view it.
Ensuring the rose plant is properly watered.
Gardeners usually use automated watering methods such as sprinklers or spray curtains that will wet the foliage, encouraging and spreading the disease to other leaves and plants.
The correct way is to water the roses at ground level. You can’t prevent rainwater from splashing on the leaves, but getting water directly to the roots reduces the time that leaves stay wet.
Consider using drip tape or drip pipe to water; this will allow tiny droplets of water at the root zones and keep the leaves above dry. This prevents the spores from splashing up.
Water roses first thing in the morning.
If you’ve been watering your roses in the evening, you’ve been doing it wrong, which could be why you’re always dealing with black spots. What! I hear you cry. It’s true. Watering in the evening means the roses are wet all night until the sun dries them off the next day.
It’s time you switched to watering in the morning. Experts highly recommend this because it allows foliage to dry off before the black spot spores start to grow. Otherwise, the spores can easily sprout when continuously exposed to a lot of moisture for at least seven hours.
Observe proper spacing
Roses thrive in a planting site with good ventilation. Therefore, you must leave enough space between your rose plants to promote good air circulation.
When air circulates freely, the leaves dry faster and reduce the risk of fungus growth. Also, if one plant becomes infected, it will not easily infect its neighbors. Densley planted roses will quickly spread the black spot disease throughout the planting area.
On spacing and circulation, pruning is essential, too; You may have heard about pruning a goblet shape when it comes to roses. This means thinning out the middle of the plant. This will prevent not only black spots but also powdery mildew.
Do not plant roses under too much shade.
While roses can still grow under partial shades, they become more prone to developing the black spot problem. The leaves will not dry quickly after rain or watering, providing good environmental conditions for fungus growth.
Warm, humid conditions allow the black spot spores to grow quickly. As such, you’ll want to grow your roses on a site with plenty of sunlight.
Prune your roses and clean up your garden
Ensure you snip off any infected leaves as soon as possible to prevent any potential spread to the rest of the bush. After that, you should also dispose of the dropped leaves immediately and properly. Some gardeners use the leaves for mulching. Unfortunately, the black spot spores can survive in the mulch and be spread back to the plant through splashing water and wind.
Pruning out the old, weak, or crowded canes in late winter is another excellent way to ensure proper air circulation in individual rose bushes. If some of the canes are infected, ensure you prune about 6-8 inches below the area showing signs of infection. Generally, it’s recommended to prune on a sunny day.
Clean your pruners with alcohol
Husbandry is very important when dealing with black spots. Always clean the pruning tools using alcohol or a 10% bleach solution before using them on another plant.
These cleaning solutions can kill mold and fungi, thus preventing the possible spread of infection through plant wounds during pruning. You can use a clean rag to rub the solution on the pruners. Remember to clean them after their last use, as black spot spores will lay dormant until you next use the pruners.
Apply a thick layer of mulch
Mulch in your garden will not only keep moisture in the soil to reduce your watering frequency but also prevent splashes of water up the plant, reducing the risk of spreading spores. A 3-inch depth of mulch around the roses is enough. However, the layer of mulch should not touch the canes.
Another thing worth mentioning is that you need to replace the mulch with a new layer, preferably after every year at the start of the spring. You can use woodchip, or my favorite is leaf mold. Leaf mold is ideal as it feeds the soil and breaks down. Suppose you want to learn how to make leaf mold. Watch the video below. It is known as gardeners’ gold for a reason.
Grow natural disease-resistant varieties of roses
Some roses are less susceptible to fungal diseases, including black spots or powdery mildew. Excellent types of roses in this category include Grandiflora roses, Meilland hybrids, drift roses, floribunda roses, and shrub roses.
Treatment solutions to get rid of black spots on roses
You can do everything right to prevent black spots, but your rose plants can still be infected with the disease. There is only so much we can do as gardeners, but we cannot control the weather like wind and rain. Both of these can carry spores to our rose plants.
Well, it happens sometimes. The good news is that this disease can be cured using commercial and homemade solutions. Without further ado, let’s check out the most effective solutions below.
Homemade, DIY solutions for black spot
1. Baking soda
Baking soda creates an alkaline chemical condition on the leaves, making it hard for the black spot spores to sprout. It is because the fungus thrives in more acidic PH conditions. This solution is more effective when you apply it as soon as you see the first signs of the disease.
Preparing baking soda spray
- Dissolve two teaspoons of baking soda in 1 gallon of warm water
- Add two teaspoons of liquid soap (Castile soap, not dishwashing soap which is a detergent and not soap) to help the main ingredient adhere to the leaves.
Apply the solution on the leaves thoroughly. Please note the rain can wash the solution off. So, it’s a good idea to spray the leaves frequently as necessary for better results. Spraying once a week is okay. Also, remember baking soda contains salts and applying high concentrations can easily ruin your leaves.
2. White vinegar remedy for black spot
You can combine ordinary white vinegar with baking soda for a more effective spray to eliminate the black spot disease.
How to use white vinegar remedy
- Mix a tablespoon of white vinegar with a tablespoon of baking soda in one gallon of water
- Add a tablespoon of canola or horticultural oil.
- Stir and shake the mixture before you transfer it to a spray bottle
Make sure you remove as many infected leaves as possible before you start spraying the mixture. Apply it weekly and after rain. However, when applying this mixture, ensure temperatures are below 80 degrees Fahrenheit.
3. Milk solution
Milk mixed with water in a 1:1 ratio can be a good natural solution for black spots. If applied weekly, this DIY solution can control the disease like a fungicide. However, nobody knows yet why milk works against black spots.
Its effectiveness is largely linked to the lactoferrin in milk, which helps fight diseases in people. It’s not any milk that’s used for black spots, though. You need to use cow’s milk. For example, soy and almond milk will not affect the roses.
Unfortunately, the milk remedy can make other microorganisms thrive on the leaves. Their presence may be aesthetically unappealing.
Commercial black spot solutions
1. Copper fungicides
If you are dealing with recurrent black spot problems, you can use copper fungicides to keep the infection under control. Demildex and Bordeaux’s mix are considered good examples of effective copper fungicides.
They work by interfering with the spores and mycelium enzyme cycle, causing permanent damage. Ensure you follow the manufacturer’s guidelines on using copper fungicides, as excessive product use can burn the leaves.
2. Neem oil
Neem oil is an excellent natural product for many pests and fungal diseases, including black spots and powdery mildew. Another amazing advantage of using neem oil is that it gets absorbed into the plant system.
So, there’s no need to reapply after rain, but you shouldn’t apply it on a potentially rainy day. And in line with that, we must say that proper application is essential to avoid injuring your roses.
Well, here are a few precautions to keep in mind.
- Do not apply the oil when temperatures exceed 90 degrees Fahrenheit or below the freezing point.
- Do not apply the oil when there is high humidity (above 90% )
- Do not apply the oil within 30 days of using the sulfur-containing products
Other products like neem oil are suitable for black spots and powdery mildew but good to be used for aphids and whiteflies; too, I speak about 5 in this video that may be of interest to you.
3. Sulfur
Sulfur can kill any fungus spores on roses. And it works pretty quickly. While this product is available in a fine powder that can be used on its own, you can also opt for the type that can be mixed with water. Such sulfur products will be labeled as wettable.
4. Insecticidal soap spray
Insecticidal soap sprays are cable of destroying the cells of microorganisms. For better results, you will want to use insecticidal soaps formulated with organic fungicides like sulfur. The soaps help ensure the leaves are well coated with the fungicide.
If you prefer chemical fungicides, you can use products like captan, mancozeb, propiconazole, thiophanate-methyl, chlorothalonil, trifloxystrobin, and triforine. Be sure to follow the instructions on the product labels to avoid the risk of serious effects on your plants.
FAQ’s
Conclusion
Roses are beautiful, and after reading this post, you could think they are not worth the effort. But following some basic principles, you can have beautiful plants with no black spots in sight.
I hope you enjoyed this blog post about black spots on roses. I trust it answers your question fully. If this interests you, why not consider checking out some of my other blog posts and subscribing to the blog, so you don’t miss future content?
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And remember, folks, You Reap What You Sow!