Roses should be full of flowers and looking their best right now, but gardeners ought to be aware that August can be a particularly vulnerable period for them due to black spot disease. This fungal infection needs heat and moisture to survive, which can cause many people to mistakenly believe it only spreads during the rainier months in spring and autumn.
However, British summers are very humid and this time of year is actually the ideal conditions for black spot, which can cause most gardeners to only spot it once it is too late. Black spot will first appear as dark circular patches on rose leaves, and soon enough, it will greatly weaken the plant so it is unlikely to grow any flowers at all.
What is frustrating about black spot is that it does outright kill roses, but it stresses them out and makes them more likely to die off from pests, disease, or extreme weather like drought.
Roses will struggle to fight off the disease and have hardly any energy, which will cause it to grow smaller and weaker blooms until it completely stops flowering at all.
While black spot is a really serious plant disease, it is fairly easy to prevent. As David Marks, a gardening expert and founder of Garden Focused, has shared, you just need a bit of cardboard.
David said: “The aim of mulching the soil around the rose bush with cardboard (or five layers of newspaper) is to trap any remaining leaves where they are.
“The spores on fallen leaves re-infect the plant when raindrops fall on the leaves and the spores splash onto new growth. A layer of cardboard will prevent this happening.”
It might sound bizarre, but mulching is the simple garden practice of placing material around a plant to protect it, and cardboard prevents spores in the soil from infecting roses.
All you need to do is place a layer of cardboard around your roses, and then place a second organic layer of mulch on top of the cardboard to prevent it being blown away by the wind.
David said: “We personally use wood chip which we have free access to. Alternatives include material from your compost heap or chipped bark. If none of those are available, lawn clippings make an excellent alternative.”
The cardboard acts as a protective barrier around your roses, while the organic mulch helps to retain moisture after watering. This keeps your roses hydrated during the hotter days of August, reducing stress and helping them stay healthy.
Mulching is a simple yet highly effective way to protect your roses from disease and encourage continued flowering well into late summer.