impatiens downey mildewWhen i first started working at the greenhouse, about 30 years ago, impatiens were the most popular plant we grew. They continued to grow in popularity and one time impatiens represented over half the bedding plants we grew.

Why Impatiens?

Everybody likes impatiens, they grow in a variety of conditions, shade tolerant, come in a dazzling variety colours and they bloom and thrive with minimum care. As an added bonus, impatiens continue blooming without deadheading.

You might wonder why then, aren’t we are growing any this year?

What Is Wrong With My Impatiens

Frequently, last season customers brought in greyish leaves or defoliated plants asking what is wrong with my impatiens?

Downy Mildew

The culprit is a fungus commonly known as downy mildew. Downy mildew is a common pathogen that afflicts a wide variety of plants, on most plants it is more of a cosmetic problem, more of a nuisance. Several years back in Europe the mildew mutated and gardeners started noticing their impatiens dying. Eventually the new downy mildew was observed in the US and with time here in southern Ontario.

Infected plants start to turn yellowish and wilty,on the undersides of the leaves you will see greyish splotches. . Before you know it leaves just start falling off leaving you with just a bunch of yellow stems.

Downy mildew infects impatiens in the garden bed then it produces spores as the fungus matures. These spores travel by splashing water into the soil waiting to grow on another plant then complete their life cycle over and over. Many people just kept growing impatiens in the same bed year after year because they put on such a vibrant carefree show. Subsequently, the mildew spores are waiting in your garden and every time you plant impatiens they will die. I have been asked how many years long spores will survive in the soil and i honestly don’t know precisely, but let just say a very long time. For practical purposes don’t plant them in infected soil ever again!

What’s Next For Impatiens?

Plant breeders produced a vast variety of impatiens series. They bred them for different colours, flower form, growth habit but they never bred with disease resistance in mind, or at least it was never a primary consideration. I have no doubt the plant breeders will come up with impatiens grown from seed that are resistant to the disease, but it will be a hard sell to consumers that experienced their plants kicking the bucket.

The good news is that their is alternatives to traditional impatiens. New Guinea impatiens are not affected and there are new affordable seed grown varieties,the ” Florific’ and “Divine” series, with awesome performance.”Bounce” is a new impatiens grown from cuttings completely resistant to downy mildew, and does exceptionaly well in hanging baskets and mixed containers. Other annuals to try would be Vinca, Coleus, Torenia or Lobelia to name a few. My favourite alternative would be begonias, more on that in my blog “Beautiful Begonias”.

As a postscript the downy mildew can also kill the herb, Basil. This year we will only be offering mildew resistant varieties of Basil.