How to check Aquilegias for disease

The weekend saw the first real gardening day of the year - the sun shone and it was warm enough to spend a few comfortable hours in the garden. We even sat and drank a welcome cuppa after all the hard work.

I also took some time outside to check on spring’s progress. There are all kinds of bulbs pushing their snouts out of the soil and plenty of fresh green growth emerging from my overwintered perennials. I paid particular attention to the leaves on my aquilegias - aka granny’s bonnets or columbine - as there‘s a new disease on the block to look out for.

Thankfully everything seems fine so far, but after reading about how downy mildew has devastated the national collection of aquilegias, I think it’s wise to stay vigilant. You may remember downy mildew was the disease that ripped through our annual busy lizzies (Impatiens) a few years ago. The result was so devastating these plants are rarely offered for sale nowadays, and have been substituted with New Guinea Impatiens instead.

The RHS has confirmed this is a different strain that affects aquilegias and it’s specific to these plants, but the signs and devastating effects of this disease are the same.

Spring is the key time to check for this disease, especially if the weather has been damp and mild as downy mildew thrives in warm, humid conditions. Firstly, look at any new leaves emerging from the soil, like I did. If they look whitish or longer than normal, then that’s a cause for concern as are any fern-like leaves with yellow patches. Compare with my photo of emerging healthy leaves.

Later on, check for signs of slug or snail damage and their characteristic trails on plants. Aquilegias are usually shunned by these as the leaves contain chemicals which are toxic to molluscs. However, they’re attracted to the mildew and start to snack on affected plants.

Plants become distorted, flower buds look shrivelled and blasted, the stems may develop reddish brownish lesions, and the leaves turn brown and die. Also look at the underside of leaves – you should see the fluffy, white growth which is characteristic of this disease.

Some aquilegias are variegated, so for these plants the disease is harder to spot. Look out for variegation which has straighter edges and which follows the leaf veins rather than the usual ‘splashed’ effect that normal variegation gives to the leaves.

Plants should be dug up and destroyed by burning on site as soon as possible. Do not add the plants to your compost heap, though plants can be taken to council compost schemes where these should reach the higher temperature needed to destroy the spores. Home composting increases the risk of spreading the disease around your garden.

Check for symptoms before buying new plants and report any signs you find to the nursery/garden centre owner or your supplier. If possible, quarantine any newly purchased plants for a few days before planting them.

If needed, water established plants carefully. As any splashes of water may help to spread spores. Ensure there is a good airflow around plants, so leaves dry more quickly and reduces the chance of the disease taking hold.

Carrie Thomas, the aquilegias’ national collection holder has lots of helpful information and photographs on her website. She’s also collating incidences of this disease, so any information you can add will be helpful. It’s been spotted in south Wales, Devon, Essex, Surrey and Hertfordshire so far.

Michelle Chapman is a gardener, freelance writer and garden blogger from Wiltshire. She writes the award winning blog, Veg Plotting, where her small town garden is a regular feature alongside any topic which springs to mind whilst at her allotment. 

Read more articles from Michelle Chapman