Friday, April 12, 2013

Downy Mildew, Why Not To Buy Impatiens This Year!


Hanging Baskets of the susceptible Impatiens walleriana ©2013 BDG
I love Impatiens for what they do in the garden.  In part to deep shade they softly fill holes in beds with color that lasts from June to first frost.  Nowadays they come in single and double flowers and just about any color and, best of all, they are cheap.  But, the Impatiens(specifically Impatiens walleriana the common bedding plant) is under attack from a devastating disease that turns the leaves yellow and ultimately strips the plant of its leaves and flowers until it is dead.  I had many clients and friends lose Impatiens last year through no fault of their own.  

I apologize for the marginal photos as they were taken with my phone at the growing facility.


Downy Mildew, a real problem for your Impatiens

4" Pot of walleriana  ©2013 BDG
Last September I wrote a piece on Downy Mildew, A Real Downer and how it had eliminated many Impatiens plantings in the area, both in the ground and in containers.  Downy Mildew is a fungal disease that has proven lethal to certain common Impatiens in the Eastern US through the midwest and down to Florida, and unfortunately there is nothing the homeowner can do about it.  Propagators and growers are completely drenching their plants in chemicals on a weekly basis just to get them to market free of infection.  Check out the following link from Sygenta on proposed preventative protocols for growing Impatiens. 


You don't even want to know about some of those products used.  All of this work and chemical application for a plant that could still die several weeks after you bring it home and it is exposed to the spores in your garden.  This can happen because the spores remain in the ground overwinter and when disturbed by splashing water, wind or shovels they can travel on the wind for miles.

Following is a very informative sheet from Ball Horticulture, one of the big guys in the plant world, on guidelines for growers: Impatiens Downy Mildew:  Guidelines for Growers.


What will happen this season

New Guinea Impatiens ©2013 BDG
I spoke with the Greenhouse Manager, Reda Barsoun, at Mahoney's, a local nursery that has a significant annual growing operation in the Boston area.  He said this year they have cut in half their growing of Impatiens walleriana and that most of them will be in hanging baskets.  Reda and his growing manager, Bobby, feel that hanging baskets have less of a chance of being infected than plants in the ground.

New Guinea Impatiens ©2013 BDG
At the nursery they will have postings warning people about Downy Mildew and offering suggestions for plants to use in their place.  I think this is responsible, since they will also mention on the post that they will not offer refunds on Impatiens.  Check out the following article in Greenhouse Grower on what the industry is doing: Greenhouse Grower article on Downy Mildew

While production of the walleriana species is cut, Mahoney's has doubled their growing of Impatiens hawkeri, or New Guinea Impatiens.  And this year, nurseries will have a relatively new Impatiens called SunPatiens, a new plant hybrid from Sakata Ornamental.  Both of these plants are not susceptible to Downy Mildew.

Range of Red New Guineas  ©2013 BDG
Most of us know the New Guinea Impatiens which does great in the sun.  It is a much bigger plant with larger and more coarse leaves and a range of flower colors that can be a little harsh, not the softer pastels you could find with the walleriana species.  The New Guinea and SunPatiens do great in the sun and part shade, but they just can't substitute for the old-fashioned walleriana species in the shade.  Reda says that the Sunpatiens tend to be more spreading than upright like the New Guinea and their flower size is in between the New Guinea and walleriana.  There will be a broad range of color choices, but you won't find some of the more subtle colors.  They will grow in deep shade but their flower production will be very light.


What to do...

Hanging New Guineas ©2013 BDG
I am not going to buy any Impatiens walleriana this year for myself or clients.  If you want to try you can buy them in hanging baskets or put them in containers, but I feel there is a good chance they will not make it through the summer.  If you plant in the ground, especially where you may have had impatiens last year that died, they will almost certainly die and quickly.  In a part shade area I am going to try some of the SunPatiens, there is a nice pale pink variety that I will let spread in an area that could use some color.

Pink SunPatiens just potted
©2013 BDG
In the deeper shade where I have some planned holes in my gardens I will plant Torenia.  I have always loved Torenia in shade containers as they are excellent at trailing and they have a good range of colors. I think this may be one of the best substitutes in the shade.

White SunPatiens just potted
©2013 BDG
Another idea in shade is Begonia.  Now, I can hear the collective groans of people who hate Begonias, but maybe you haven't seen some of the dazzling Begonias available.  So often we think of the little, waxy leafed plants with tiny flowers we see in the nursery or on our grandmother's windowsill.  There are some beautiful big flowered begonias with some amazing flower colors like the "Dragon Wing" series or tuberous Begonias.

Violet Torenia @ Proven Winners
There are some fantastic Coleus that have wonderful foliage color to add contrast and color in the shade.

Check out my blog post from last fall for some other ideas.

Pink Dragon Wing Begonia
@ Proven Winners
We may end up seeing Impatiens walleriana disappear for a few years and I am sure that some scientist will come up with a new variation that is resistant to the disease.  I hope so, because I will definitely miss this plant in my deep shade garden.








Spring is progressing -- Pushkinia, Scilla, Crocus and Daffodil
with Muscari coming in next couple of weeks.  ©2013 BDG




















3 comments:

  1. I can see going with Browalia and Coleus, but I'm not a Begonia or Torenia person.

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  2. I have to admit that I am not an impatiens fan (we don't use them at Blithewold) and am actually looking forward to seeing some new and different things in other shady gardens in the neighborhood!

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  3. I have not bought them for my garden or ordered them for clients for three years now. The problem started enforce about that long ago and Cooperative Extension here has been warning on it for that long. Just this year, the independent nurseries are not bringing them in. A friend of mine also just posted on this and really I am surprised people were not posting sooner. I think I only saw one post last year besides yours. It is good to get the word out like you are doing, because I believe the big box stores are still selling them and like you said, the chemicals used on them are very worrisome.

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