Impatiens flowers with yellow leaves

Downy mildew attacking many impatiens

October 22, 2013 – 09:01 am

A flower of small yellow

New Guinea impatiens are resistant to the downy mildew that has plagued common impatiens. (Robin Carlson, Chicago Botanic Garden photo)

I had bad luck with my impatiens last year. They turned yellow and lost all their leaves in summer. What can I do to avoid this happening again?

— Jerry Hopkins,

Evanston

Your plants may have had downy mildew. This disease of impatiens has been observed in the United States since about 1994 but became more widespread and destructive last year. Cool, wet weather likely was a factor, as the downy mildew pathogen thrives under those conditions.

The disease affects common impatiens (Impatiens walleriana), while New Guinea impatiens (I. hawkerii) are highly resistant to it. Symptoms include new leaves that are small or discolored (yellow or pale green); stunted growth overall with yellowish foliage; flower buds that fail to form; leaves that curl downward; and a fluffy white coating on the lower surface of leaves. As the disease progresses, the plants will become barren stalks with one or two yellow leaves left.

Keep in mind that impatiens plants also can be stunted and have yellow leaves if they were allowed to dry out repeatedly when young, so consider how the plants have been maintained before you diagnose downy mildew. Plants that were stunted by dry periods will recover with adequate watering, but plants infected with downy mildew will continue to decline.

The disease pathogen can overwinter in plant debris and soil. So if your beds of impatiens were infected in 2011, consider breaking the reproductive cycle of the disease by using different shade-tolerant annuals in those spots this year, such as New Guinea impatiens, coleus or begonias.

Downy mildew is more likely to develop when impatiens' foliage remains wet for extended periods of time; when temperatures are cool (especially at night); and during periods of high humidity. Impatiens that are planted very close together and in heavy shade are more at risk.

There are fungicides that can give some protection, but first focus on culture and plant selection to mitigate this disease in your garden. Start with healthy, uninfected plants.

Space them out to allow air movement between the plants, which will help reduce humidity and leaf moisture. Water in the morning so plants have time to dry out before nightfall.

Monitor your impatiens all through the season and immediately discard any plants that show downy mildew symptoms in landscape waste bags, not in your compost.

Impatiens are an important plant for the shade garden, so I do not see any reason to completely stop using them in the landscape. Greenhouses producing impatiens should monitor closely for this disease and discard any infected plants prior to sale.

Source: articles.chicagotribune.com


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You can have a lot of fun with that

Not sure if you also asked in the gardening forum, but they can be very helpful, too.
Until I bought a place with a tiny, shady yard, I had no idea how many great plants there are for shade.
I suggest raised planters, because small pots on the ground aren't very lush-lloking. Google "raised planters" to see ideas for making and buying them.
A lot of ivies and other shade-loving ferns are too invasive to plant in the ground, but you can get a lot of mileage out of them in a container. Google "plants for shade" and "vines for shade".
You'll probably want an inexpensive trellis, either against a wall or to act as a screen


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