The nation's favourite summer bedding plant has been uprooted from the beds of the country's biggest garden centres due to an outbreak of an airborne and fungicide-resistant mildew.
It is thought many large garden retailers such as B&Q and Homebase, as well as seed supplier Thompson and Morgan, have withdrawn or reduced stock of the plant, which was almost entirely wiped out by impatiens downy mildew last year. The disease attacks busy lizzies with a white powder on the underside of leaves, causing them to turn yellow and fall off, leaving bare stems.

Experts from the Royal Horticultual Society have warned retailers who are still stocking busy lizzies to keep a close eye on them for signs of the disease. One of the most worrying features of the mildew is that it leaves infected spores in bedding soil for up to five years following a break-out.

RHS chief horticultural advisor Guy Barter told DIY Week: "For those retailers stocking the plant I would strongly advise them to let their customers know about the disease. Do not plant busy lizzies in the same spot as last year and, if they're in a container, change the potting media.

"Impatiens downy mildew thrives in damp, airless conditions so keep stock in dry areas with a good airflow. I would also advise retailers to ask searching questions of their suppliers, growers will be aware of the strain and can reassure garden centres."

It is thought the mildew was inadvertently imported with infected cuttings from Israel last year. The disease infected not only other cuttings but seeds as well, which several garden centres then unknowingly sold to customers.

Mr Barter added: "No one who sells busy lizzies wants to disappoint their customers, and the nature of this particular mildew means they can't guarantee each sale is risk-free. So, sadly, many are sitting on their hands this year."

The RHS have issued a fact sheet on their website for gardeners and retailers stocking busy lizzies, warning them of the signs and affects of impatiens downy mildew.