2013 Update

Substitutions for the Shade Garden

Avoid Impatiens walleriana again this year, due to the disease problems associated with everyone’s favorite summer annual. Click HERE to read the 2013 Downy Mildew Update. 

First the good Impatiens news: you can still use SunPatiens and New Guinea Impatiens, as they are not affected by downy mildew. Both varieties offer many flower and foliage selections, and they will tolerate more sun than Impatiens walleriana.  

For other shade garden plants, consider Heliotrope’s lovely violet-purple flower clusters which are also fragrant, making this a perfect container garden or borden garden choice. Fuchsias look lovely dripping from a hanging basket or container garden. How about Coleus? The riotous foliage combinations work well with just about any flower garden favorite: there are trailing Coleus and upright Coleus to suit every need, and they make excellent bedding plants. Consider the Begonia (and I’m not talking about the “wax begonias” planted en masse in front of every subdivision and shopping center across the country). Look for the dark-foliage or spotted-leaf Begonias, dragon-wing and angel-wing Begonias, dripping with flowers from spring through late fall. There is simply nothing more elegant, and they will triple in size over the growing season. Nicotiana is a fragrant, shade tolerant annual, and it’s also deer resistant. 

There will be plenty of choices for the shade garden this summer, so keep your eyes open. 

Map showing the states infected with Downy Mildew.  Much Ado about Impatiens! 2013 Downy Mildew Update Downy mildew is still with us, overwintering in our soils, and that’s a problem for everyone who loves Impatiens walleriana, the favorite shade garden annual. Last year it spread across the northern Seaboard and through the Southeast and to Texas. Reports of the disease were also documented in California, Oregon and Washington.   The disease is spread two ways: (1) by plants that are already infected with the pathogen and purchased by consumers and landscapers who plant them in their gardens; and (2) from spores spread by rain or irrigation (which splashes spores onto neighboring soils), and by wind currents which carry the spores to new territories.  Plants infected with the disease become defoliated after being installed in the landscape, leaving nothing but withered green stalks devoid of foliage and flowers. This is known as the “green stick syndrome.” (Earlier in the growing season, infected plants will be stunted, remain small, and fail to thrive.) Infected Impatiens and all their leaves and flowers should be removed immediately and disposed of - do not compost the diseased plants, and do not replant Impatiens walleriana in the same bed, because spores will overwinter and reinfect plants again the following season.   Spores remain in the soil for years after the disease has been introduced. The pathogens, known as “oospores,” have over-wintered in Delaware and New York (Zone 5), indicating that the spores are resistant to very cold temperatures. No one has yet determined at what winter temperature the spores may die. Because the spores over-winter in the soil, they germinate again in the spring, which begins the process of infection all over again, if Impatiens walleriana are re-planted in the same location.   Once the soil has become infected with downy mildew, do not replant Impatiens walleriana in the same flower beds. It is not yet known how long the disease will remain in the soil, but it is assumed it could be many years based upon the studies at Ball Horticultural Co.  The above information was obtained from the 2013 report by Dr. Colleen Warfield and Nancy Rechcigl at ANLA, and at Ball Publishing, HERE. So what can you plant in the shade this year? Click HERE for some ideas.  

Map showing the states infected with Downy Mildew. 

Much Ado about Impatiens!

2013 Downy Mildew Update

Downy mildew is still with us, overwintering in our soils, and that’s a problem for everyone who loves Impatiens walleriana, the favorite shade garden annual. Last year it spread across the northern Seaboard and through the Southeast and to Texas. Reports of the disease were also documented in California, Oregon and Washington.  

The disease is spread two ways: (1) by plants that are already infected with the pathogen and purchased by consumers and landscapers who plant them in their gardens; and (2) from spores spread by rain or irrigation (which splashes spores onto neighboring soils), and by wind currents which carry the spores to new territories. 

Plants infected with the disease become defoliated after being installed in the landscape, leaving nothing but withered green stalks devoid of foliage and flowers. This is known as the “green stick syndrome.” (Earlier in the growing season, infected plants will be stunted, remain small, and fail to thrive.)

Infected Impatiens and all their leaves and flowers should be removed immediately and disposed of - do not compost the diseased plants, and do not replant Impatiens walleriana in the same bed, because spores will overwinter and reinfect plants again the following season.  

Spores remain in the soil for years after the disease has been introduced. The pathogens, known as “oospores,” have over-wintered in Delaware and New York (Zone 5), indicating that the spores are resistant to very cold temperatures. No one has yet determined at what winter temperature the spores may die. Because the spores over-winter in the soil, they germinate again in the spring, which begins the process of infection all over again, if Impatiens walleriana are re-planted in the same location.  

Once the soil has become infected with downy mildew, do not replant Impatiens walleriana in the same flower beds. It is not yet known how long the disease will remain in the soil, but it is assumed it could be many years based upon the studies at Ball Horticultural Co. 

The above information was obtained from the 2013 report by Dr. Colleen Warfield and Nancy Rechcigl at ANLA, and at Ball Publishing, HERE.

So what can you plant in the shade this year? Click HERE for some ideas.  

Not surprisingly, I didn’t get too many people interested in the photo-post about the disease-ridden Impatiens walleriana, so let’s see if we get more interest in the “pretty plants” gardeners can use this summer, while Impatiens are on hiatus (at least as far as my clients are concerned). (And if you don’t know why you shouldn’t use Impatiens walleriana this summer, check out the link above.)

First the good Impatiens news: you can still use SunPatiens and New Guinea Impatiens, as they are not affected by downy mildew. There are many flower and leaf colors to choose from, and these two types of Impatiens will tolerate more sun than the shade Impatiens walleriana.  

For other shade garden plants, Heliotrope is not only a lovely violet-purple, but it is also fragrant, so it’s a perfect container garden or borden garden choice. Fuchsias look lovely dripping from a hanging basket or container garden. Coleus? The riotous foliage combinations work well with just about any flower garden favorite: there are trailing Coleus and upright Coleus to suit your every need (and they make excellent bedding plants). And lastly, the Begonia (and I’m not talking about the “wax begonias” planted en masse in front of every subdivision and shopping center across the country). Look for the dark-foliage or spotted-leaf Begonias, or dragon-wing and angel-wing Begonias, dripping with flowers from spring through late fall. There’s nothing more elegant. 

There will be plenty of choice for the shade garden this summer, so keep your eyes open. 

Spring-Summer 2012 Plant Alert: The author of this blog will not be using any Impatiens for installations during the upcoming planting season.  Following the lead of my local nursery suppliers, none of our installations this spring and summer will include Impatiens. The reason for this is Downy Mildew. (Above: University of Illinois Trial Gardens 2011, reported by Stephanie Porter, University of Illinois Extension.) Quoting from my local supplier, Saul Nurseries, February 2012: Downy mildew is a particularly insidious pathogen. In the landscape, it is often difficult to identify until it’s too late. Even if it is caught in time a strict and arduous spray program must be instituted to control it.  Spores of downy mildew may persist in the soil for years. In the U.K., where impatiens are the top selling annual, down mildew has been devastating…. In the U.S., confirmed reports of downy mildew were sporadic but ranged from central and southern California to the Niagara region of Canada and the Midwest. Simply put, and for obvious reasons, Saul Nurseries does not want to sell plants that may be infected. And neither do I. Complete information can be found at the Southeastern Ornamental Horticulture Production and Integrated Pest Management site. 

Spring-Summer 2012 Plant Alert: The author of this blog will not be using any Impatiens for installations during the upcoming planting season. 

Following the lead of my local nursery suppliers, none of our installations this spring and summer will include Impatiens. The reason for this is Downy Mildew. (Above: University of Illinois Trial Gardens 2011, reported by Stephanie Porter, University of Illinois Extension.)

Quoting from my local supplier, Saul Nurseries, February 2012:

Downy mildew is a particularly insidious pathogen. In the landscape, it is often difficult to identify until it’s too late. Even if it is caught in time a strict and arduous spray program must be instituted to control it.  Spores of downy mildew may persist in the soil for years. In the U.K., where impatiens are the top selling annual, down mildew has been devastating…. In the U.S., confirmed reports of downy mildew were sporadic but ranged from central and southern California to the Niagara region of Canada and the Midwest. Simply put, and for obvious reasons, Saul Nurseries does not want to sell plants that may be infected.

And neither do I.

Complete information can be found at the Southeastern Ornamental Horticulture Production and Integrated Pest Management site.