When I type the phrase ‘black spot on roses,’ my mind instantly and peversely adds ‘and whiskers on kittens.’ But unlike the famous song from The Sound of Music, black spot is certainly not one of my favourite things! Indeed Julie Andrews may have been able to stay chipper in the face of dog bites, bee stings and feeling sad, (and all those warbling children!!) but I struggle to maintain my sense of humour in the face of this fungal disease.
And as someone with a cottage style garden and therefore plenty of roses, I face black spot quite a lot. Indeed, I spend a lot of time puzzling over (and researching) how to deal with it. So I thought I’d share the top tips I’ve gleaned along the way.
Black Spot on Roses – what is it?
Black spot is one of the biggest problems you will get with roses. (If you discount pruning, which I also find a nightmare as I’m so rubbish at it!)
Black spot is caused by a fungus which infects the leaves. It starts in Spring and the tell tale signs are enlarging purplish or black patches which appear on the leaf’s surface. The area around the spots may go yellowy too. The leaves then often drop off. Obviously, this all massively inhibits the vitality of the rose. After all a plant without its leaves during its growth period isn’t a happy plant!
A rose with black spot may also have small, black, scabby lesions on its stems – especially its young stems.
Sometimes the spots on the leaves remain quite small, and the leaves don’t drop off. Sadly, even if the leaves stay on, Houston, you still have a problem. That’s because diseased leaves don’t work properly so well, inhibiting the poor old rose’s feed intake.
According to the experts, the fungus behind black spot (Diplocarpon rosae) is genetically very diverse and new strains develop pretty quickly. This means that although clever rose breeders are constantly developing new black spot resistant varieties, this resistance usually fails to last. New strains of the fungus develop which they’re not resistant to!
In short, if you have roses, you are likely to encounter some black spot. And I have masses of them. I’ve roses in beds, borders, climbing walls, in containers, framing doorways and scrambling over ugly sheds!!
Black Spot on Roses – The Organic Answers
The disease is easily spread on the wind, and the fungus spends the Winter on fallen leaves. The spores are then in a prime position to pounce and infect your plant in the Spring.
Pick Up Leaves
So if you’ve black spot on roses, remove the diseased leaves and pick up and destroy any that have fallen. I find this a real challenge. I get into quite a scratchy tangle trying to pick up the leaves around thorny roses. But do persevere.
Also, when pruning, cut out any stems with black spot on. Once you have gathered everything that’s diseased up don’t put the debris on your compost heap. Properly get rid of it all.
Mulch
In March put a thick layer of mulch (1-2inches deep) around the base of your roses. I do this every year. Indeed, it’s one of my top gardening jobs for March This gives the roses a nutritional boost, keeps weeds at bay and helps retain moisture for them. However, it’s also particularly helpful to roses which suffer from black spot. That’s because it prevents rain splashing the spores in the soil on to the new growth.
There are lots of things you can use as a mulch. Good quality garden compost, composted straw or bark, or well rotted manure from a local farm. But remember, if you’re using manure it needs to be at least 2 years old. Fresh manure can burn the roots of your roses. The mulch needs to be spread to the width of the rose’s canopy (and keep it away from the rose’s stem).
Of course you should weed, removing all the fallen leaves before you mulch (there’s no escaping that task folks!) Also water your rose before mulching, and feed it too. The experts at David Austn roses suggest mulching in March/early April, immediately after the first feed. Also, if, by Autumn, your layer of mulch has disappeared, think about adding a second mulch before Winter. I’ve not done a second mulch like this before but will definitely give it a go.
Watering
Another tip I’ve gathered is about watering. Water your roses at the base of the plants, not the leaves. Ideally water first thing in the morning, so that the warmth of the day will prevent a damp atmosphere forming around your rose (as a damp atmosphere is the environment within which the spores will thrive and spread).
Feed
To me, it makes a lot of sense that feed will be a key weapon in your fight against black spot. After all, like humans, the healthier roses are, the better equipped they will be to fight off diseases such as black spot. David Austin suggests feeding twice a year. In March/early April plus in early July, after the first flush of flowers to encourage further blooms.
However, my lovely neighbour, Desi, has introduced me to an alternative organic rose feed, that requires a different approach. Let me introduce you to Uncle Tom…
Call in Uncle Tom
No Uncle Tom isn’t a hedgehog (I just love that picture!) Uncle Tom is a rose tonic. It’s a natural rose feed which is ideal for gardeners like me who don’t like to use chemicals on their garden. This makes it very bee, insect and butterfly friendly. And a garden that’s friendly to them will be much friendlier to other wildlife too. (If you want other ideas for attracting wildlife into your garden you can see some tips here)
Anyway, back to Uncle Tom. It comes in a funny looking bottle and a little goes a very long way! You just add 10ml to 1 litre of water and drench the soil around your poorly rose to give it a boost. You then use it every 7-14 days from April to October as a drench or rose spray (again I’d use it in the day not the evening as you don’t want overnight dampness).
I’ve only just started using this magical mixture so it’s too early to say if it’s working, but Desi has used it for over a year and her roses are looking brilliant!
Black Spot on Roses – A Natural Treatment
The methods so far will inhibit and deter black spot on roses. But if you actually want to try to treat it, and are not against using chemicals in your garden, you will find ones to buy. However, I don’t want to go this route. So am going to try this alternative treatment which I’ve unearthed.
- 1 heaped teaspoon of bicarbonate of soda
- 1 tablespoon of vegetable oil
- 1 teaspoon of organic washing up liquid
- 1 gallon of water
Simply mix these ingredients together, put them in a sprayer and use every 7 days – applying to the leaves and base of your rose.
Belt and Braces!
I’m going to add this natural treatment, to my new Uncle Tom regime. I’m also going to add a mulch in Autumn as well as Spring. These tricks, combined with the meticulous picking up of all affected leaves, and the removal of diseased stems and leaves, will hopefully help me keep the dreaded black spot at bay.
I can’t sing like Julie Andrews, I’m no nun, and I’m certainly not 16 going on 17 (in my dreams) but I’m hoping this combination of remedies will ensure treating black spot on roses becomes less of a song and dance!
See what I did there !! Happy gardening x
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