Downy mildew destroys local impatiens

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The undersides of these yellowed, down-curled impatiens leaves The undersides of these yellowed, down-curled impatiens leaves show spores of white downy mildew. Photo Credit: Cornell University / M. Daughtrey

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Jessica Damiano Jessica Damiano, Newsday columnist

Jessica Damiano is a master gardener and journalist with more than 20 years experience in radio, television, print

Impatiens have always been among the easiest bedding and container plants to grow in the Northeast. We gave them some shade and some water, and they took care of themselves, rewarding us with colorful flowers all summer long.

Unfortunately, that hasn't been the case this year, and it looks like it won't be next year, or for the foreseeable future.

All over the region, gardeners have become painfully aware that their go-to summer workhorses haven't been up to the task. Leaves turned yellow and fell off, plants were severely stunted, and those who looked closely noticed the presence of a white substance under leaves. For some, there was the bizarre "disappearance" of plants altogether. These are symptoms of downy mildew, a ravenous disease that has affected local basil the past few years and this summer moved on to impatiens with a vengeance.

So, what to do? Sorry to be the bearer of bad news, but if your impatiens are infected and still in the ground or in pots, you absolutely must give them up; there's no saving them. Bag them tightly in plastic (to contain the spores) and place in the trash. Leaving them in the ground or in pots would allow spores to spread to other plants and increase the pathogen's presence in the soil, where it will survive winter. (For pots, discard the soil in the same manner and disinfect containers with a 90/10 water/bleach solution. This won't help impatiens next year, but it will offer a clean, healthy start for your other plants.)

Make no mistake: This is a serious disease, and it just might spell the end of impatiens on Long Island. "The best and really only way to avoid a reoccurrence is to plant something else," said Cornell University plant pathologist Meg McGrath, who is based in Riverhead and has been tracking the disease's progression. The pathogen can be transmitted from infected seeds, on leaves or via airborne spores, and planting impatiens next year -- even in another location -- will just feed the hungry beast.

Although we may be mourning the loss of impatiens in the Long Island landscape, McGrath is a glass-half-full type of gardener, suggesting we turn these lemons into lemonade and see it as an opportunity to embrace some new plants. I couldn't agree more.

Greenhouse growers who produce impatiens are responding to the outbreak and are working to find suitable substitutes to grow for next year. New Guinea impatiens, for instance, are not susceptible to downy mildew, so they would make wonderful alternatives. Petunias are lovely, too. And as a bonus, both can handle more sun than the garden-variety impatiens.

During the off-season, I'll talk to growers and scour around for exciting alternatives for us to plant in 2013. I'll report back early next spring, just in time to help you plan your new garden.

 


DEAR JESSICA: Enclosed is a picture of a plant that started out small a year ago and continued growing. It's now about 12 feet high, with three stems of yellow blossoms. I have been told it is an herb called mullein. I have been curious about how to use it. I would also like to know whether it is normally found growing in this area and whether it throws off seeds.-- Robert Hamill, Southold

 

DEAR ROBERT: You've been given good information. Your weed is, indeed, common mullein (Verbascum thapsus). It usually pops up in sunny patches of soil in fields or ditches, or areas that have recently been disturbed, such as by fire.

Mullein's tall, pretty flower spikes can reach 10 feet tall. The plant is a biennial, which means it completes its entire life cycle in two years. The first year, the plant is just a rosette of soft, velvety leaves, which survives the winter and sends up a flower stalk in the second year. The flower blooms all summer long and can produce thousands of seeds before the plant dies. The seeds can survive in the soil for as long as 100 years, waiting for conditions to be right for another plant to grow.

All parts of the plant have been used in alternative medicinal preparations: Tea brewed from leaves (and carefully strained) is said to treat respiratory ailments; the plant's flowers are infused with oil and used to treat minor cuts, diaper rash and minor earaches; its roots have been used to treat urinary tract infections. Dried leaves are an ingredient in some herbal cigarettes, and fresh ones -- when crushed and rubbed on the skin -- are said to work as an insect repellent. (Keep in mind there is no scientific research to back any of these claims, and no guarantee of safety; please check with your doctor before using this plant in any of these ways.)

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