Gardeners across the UK can protect their roses from black spot disease with a simple five-minute task performed once a week during summer, according to gardening expert Ish Kamran. The key is planting salvias alongside rose bushes, as these purple-flowered plants act as natural antifungals.
Black spot disease thrives in warm, damp conditions, which are common after a heatwave transitions to wetter weather. The fungal infection first appears as dark patches on leaves, causing them to drop prematurely. If left untreated, it can strip a rose bush of all foliage, preventing it from producing energy for flowering and ultimately killing the plant.
Why Salvias Work
Ish Kamran, gardener and founder of Gardening with Ish, explained: "Keeping [rose bushes] light, airy and making sure it is adequately watered but not overly watered is key. But the other thing you can do is actually grow salvias around your rose bushes. Salvias are natural antifungal plants, and by having them nearby, they help prevent fungal infections in the first place."
Salvias grow upright with spiky purple blooms, a structure that encourages greater airflow around neighboring plants. Since black spot spreads through water and is more likely to infect leaves that remain damp for extended periods, improved evaporation reduces risk. Positioning salvias around roses helps moisture on foliage evaporate quickly, which is especially beneficial during wet summer conditions.
Treatment for Existing Black Spot
If black spot has already appeared, early detection makes it easier to manage. Ish recommends removing infected leaves immediately and spraying the plant. Commercial sprays like Rose Clear are effective, but a homemade organic spray can be made by mixing one teaspoon of bicarbonate of soda in a spray bottle of water. "Lightly mist over the top every week or so, and that should hopefully clear it," Ish said.
Bicarbonate of soda is an alkaline compound that makes it harder for fungal spores to proliferate. It slows the disease, allowing healthier leaves and stems to grow. Gardeners should inspect rose bushes every few days during summer, especially after rain. Infected leaves should be disposed of in the bin, not composted, to prevent spores from spreading.
Ongoing Care
Regular pruning and proper watering are also essential. Ish emphasizes that roses need adequate water without being overwatered, as damp soil can encourage fungal growth. With weekly inspections and the addition of salvias, gardeners can enjoy healthy, blooming roses throughout the summer months.
