Garden Q&A: What is the best way to avoid blackspot on roses?

Whether you're a gardening beginner or expert, Irish Examiner columnist Peter Dowdall has the answer to your questions

QUESTION

I want to avoid blackspot on my roses this year. On occasion, in your Garden Q&A, you've previously recommended copper sulphate. 

I understand that you have to use "hydrated lime" in the mixture; is this correct? 

Also what ratio of mixture to water should I use?

ANSWER

Copper sulphate mixed with water will work well on its own to protect roses from fungal blackspot later in the year. 

Hydrated lime is often added and when mixed in this way it is referred to as Bordeaux mixture and there are various formulations and rates. 

Bordeaux mixture and, to the best of my knowledge, liquid copper sulphate are both banned for use as garden fungicides due to the potential harmful build-up of copper in the soil.

However, copper mixture sold in garden centres in a powder form works equally as well in my experience. 

But, do please, apply sparingly, at most once a year. To get the best effect, apply it at the right time which is at “bud burst” when the leaves are bursting forth from the dormant buds.

You could also try using a mixture 1:1 of milk and water. Spray your roses with this every week or so during the growing season and it works very effectively as a natural fungicide.

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