Lovers of Impatiens rejoice!
Gardeners here have been biting their nails since 2012, when a ravaging disease called downy mildew came to Long Island and robbed us of our beloved, go-to shade-loving annuals.
What you might not have known is that every year since, as you read annual warnings of doom in this very column, researchers have been working to develop new, disease-resistant old-time impatiens.
One new series, Imara XDR from Syngenta Flowers, was shown to be highly resistant to the disease in trials conducted in 2017 and 2018 at Cornell University's Long Island Horticultural Research & Extension Center in Riverhead. The plants are finally available for purchase, and come in rose, red, orange, violet, white, and with a patterned orange star, as well as in containers with mixed colors. Expect them to grow 12 inches tall and wide with a mounded habit, just like your long-lost friend.
This is great news, to be sure, but it comes with a catch: The folks at Syngenta tell me that "since the market for impatiens is undifferentiated (until now), plants will be sold with mostly generic tags, so Imara XDR will be hard for consumers to identify."
To help identify the "new" impatiens when shopping, the company recommends that consumers do three things: "Shop at the big-box stores that are supplied by our top grower partners (Lowe's, Walmart and The Home Depot all have growers producing commercial quantities going into stores now); look for very healthy plants _ (Downy mildew) moves in quick, and if the plants are susceptible, they usually look pretty bad at retail; look for the tag. We do have many growers that call out varieties, even in generic categories."
It's not perfect, but if garden centers no longer sold the original plants (many don't, but as of last year, some still did), there would be no confusion. I recommend asking the garden center manager if the impatiens being sold are specifically Syngenta's Imara XDR (XDR stands for "Xtreme Disease Resistance").
That's important, because, although the new varieties are considered immune, downy mildew has shown no sign of retreat. Plasmopara obducens, the pathogen that causes the water-mold disease, lives in the soil (surviving from one year to the next) and is carried by airborne spores. It thrives best when temperatures are warm during the day and cool at night, further aided by rain or overhead watering, which carries spores to other areas. The disease was identified on Long Island last year, so it's a fair assumption it's still around.
