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Danger! Aquilegia downy mildew alert

During the last couple of weeks I have spent many many backbreaking hours spread over several heartbreaking days digging up and burning every aquilegia (one of my favourite cottage garden plants at this time of year), just as they were coming into flower in my garden. Why? It had gradually dawned on me that they had aquilegia downy mildew.

Aquilegia with aquilegia downy mildew

Aquilegia with aquilegia downy mildew

Aquilegia leaf with aquilegia downy mildew

At first I had thought I was getting some interesting new seedlings; small silvery-leaved plants were appearing. Then I spotted some rather more lime-green or golden plants, and some with rather nice, subtle variegation. As I have never had variegated aquilegia cultivars in the garden before I realised it was too much of a coincidence that this should all be happening at once and thought back to a report from a couple of years back of a new disease outbreak wiping out the National Plant Collection of Aquilegia. I looked through their website and there were photographs resembling all my “interesting new seedlings”: actually showing various stages of the disease.

Aquilegia leaves with downy mildewThen the silver plants started to twist and collapse, and some variegated ones, on closer inspection, were a bit more ugly and extreme, especially the lowest rosette of leaves. There was also a lot of purple mottling.

Other plants just didn’t look quite right: the leaves were narrower and more wedge-shaped than usual. Then the flowers, when they started to appear, often looked rather bleached at the tips of the petals and occasionally twisted or deformed. Sadly, the plants have all had to go, even the few that at first I had thought looked relatively healthy.

Although related to other downy mildews, this horrible disease seems to be specific to aquilegias (columbines, granny’s bonnets) and has only been identified in the last few years. Nobody knows where it has come from: it doesn’t seem to have been imported from abroad (unlike so many new pests and diseases). But it has spread around the country like wildfire. It seems there is no effective chemical control: systemic fungicides are not recommended by the RHS advice pages. Burning, or deep burial in the vegetable plot are their only suggested options (but I would have thought that the danger of accidentally unearthing the festering corpses would be too great in the latter case).

Judging by the number of plants that I had to dig up, the disease had been with me for some time (one year at least, probably two), and now that I know the symptoms I have started to notice it in many other places. Most notably a well-known Grantham DIY emporium, which was selling packs of clearly diseased plants (but member of staff took two packs, immediately looked up the RHS page on his smartphone and promised to report the problem to the head buyer), and a Grantham garden centre (where the staff member seemed vaguely interested but hadn’t bothered to remove their spectacularly diseased display plant from show a couple of hours later).

Aquilegias with downy mildew in DIY outlet Aquilegias with downy mildew in DIY outlet

I suspect this is the problem: the small plants on sale at the DIY outlet must already have had the disease when they were sent out from the nursery that raised them. The large plant at the garden centre was probably also sent out from a central supplier. It only takes one or two such suppliers to send out sickly plants to chains of retailers and independent outlets around the country to spread a disease in no time. And even though this downy mildew is specific to aquilegias, I suspect that its resting spores, which are released into the soil (and hence the wider environment) from the rotting leaves, can probably be passed around in pots of other plants that have stood near to the infected aquilegias. I only hope I’m not guilty of innocently spreading it to any other gardens that I have visited or donated plants to before realising that I had the disease here.

Do I sound paranoid? I am. My wife has just come home from visiting a friend a couple of villages away, who had just said to her, as she left, “Isn’t it dry? Look at my aquilegias!” She broke the news as gently as she could…

(PS It wasn’t us who had passed on the mildew to them! We haven’t been to their garden, nor they to ours, in the last couple of years at least.)

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