Alliums and blackspot

Hello! I keep reading that the planting of alliums alongside roses can reduce blackspot. Is this just a rumour that’s got out of hand or do any of you know of any conclusive evidence?

Hello James_D!
I haven’t tried this recipe myself in this case, but the attached scientific paper proves your thesis because this study shows, that Allium is at least on the second place in the ranking after Neem oil, which could probably show phytotoxic effects.Therefore Allium is best recommended for organic farming. I’m sure it’s worth a try.
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This is in applying a solution which has allium in it? I’m reading people just planting it around roses to help with black spot. Which would be nice, get a flower and reduce blackspot at the same time

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I’d imagine you would have to apply a solution containing the allium to reduce the black spot. Simply planting them with the roses would have so little effect on the actual rose tissue or the air surrounding both plants, I can’t see how they could have any effect. It’s probably as effective as the wives tale stating planting marigolds around your roses prevent spider mites and Society Garlic prevents snails. The marigolds were SMOTHERED in spider mites and their webs which quickly moved over to everything else and were only eradicated when the marigolds went into the trash and I bought a water wand and began using it. The Society Garlic was THE favored hide out of all the brown snails. Kind of perverse if you think about it. Garlic with snail… If I wanted to thin the herd, all I had to do was comb through the garlic and smash them on the street.

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My thoughts also! Many old wives tales in Britain when it comes to gardening. This one baffles me as it’s on the royal horticulture society and gardeners world websites! It makes more sense that an application would prevent black spot. It’s an odd one as other than that article above, I have seen no evidence and so many places pushing this nonsense… I guess I wish magic was real!

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Don’t we all? LOL! It would make many things SO much easier and probably more fun!

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I plant Allium (sativa → garlic) next to my roses to keep away ants that put aphids on my roses. I’ve noticed in the meantime that it doesn’t keep the ants away, but I imagine there would be a lot more ants with aphids if I didn’t plant them :stuck_out_tongue:
The garlic benefits from the fertilizer I give my roses and in summer and autumn I occasionally pick some fresh garlic. It’s more of a convenience than a solution.
I cannot believe planting garlic would reduce blackspot. What is true about garlic and Allium in general is that those plants contain more sulphur than other plants. So maybe in fall, when the infected leaves fall to the ground and mingle with the leaves of the Allium, the sulphur released when the Allium foliage decomposes affects the spores or the black spot fungus. Sulphur is used to reduce fungus on many types of plants. But that is just an idea that just popped up. So no scientific data on it what so ever. I’m really sceptic about the benefits of Allium planted alongside roses to keep blackspot away. You can’t fight it.
Plant and breed healthy roses. Put them in a spot they like. Feed them, water them. Don’t keep the diseased ones.

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I’m of the feeling that you breed healthy roses put them in the right place, water, feed and then try all magic possible that’s not chemicals to make them shine

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