Is it safe to plant impatiens this year?

Answer

Impatiens downy mildew, caused by the water mold pathogen Plasmopara obducens, was identified in the US in 2004 and became widespread in our area in 2011. It has caused severe defoliation and flower drop of impatiens, usually by mid-summer. Unfortunately, this blight is not going away. Most varieties of Impatiens walleriana, the traditional bedding plant, are highly susceptible to this disease. The pathogen's spores spread easily via wind and water and can remain in soil over the winter and then reinfect plantings for 5 years or longer. Infected plants do not recover and have to be removed. Fungicides are not effective. Balsam impatiens, I. balsamina, is also susceptible, although damage is usually limited to yellow spots on leaves.

As of 2023, new disease-resistant Impatiens walleriana types have been introduced and trialed, giving evidence that some selections of this classic summer bedding plant may be safe to plant again. Imara XDR® impatiens from Syngenta Flowers have been confirmed to have high disease resistance to impatiens downy mildew in trials at Cornell University’s Long Island Horticultural Research & Extension Center. Beacon® impatiens from PanAmerican Seeds are considered highly resistant to impatiens downy mildew and showed outstanding results in Penn State's trial gardens, where they scored slightly ahead of the Imara XDR® impatiens. Keep in mind that even highly disease resistant impatiens are not entirely immune to disease, but they are substantially less impacted by impatiens downy mildew.

The Beacon® plants are slightly more compact than the Imara XDR® plants which offer a greater selection of colors. You can find information on the colors that are currently available and where Beacon® plants can be purchased from their breeder PanAmerican Seeds. Information on Imara XDR® impatiens are available from Syngenta Flowers.

There are other impatiens that have been filling in for the vulnerable I walleriana for the past few years.  New Guinea impatiens, I. hawkeri, is immune to impatiens downy mildew. New Guinea impatiens plants are larger than I. walleriana, with larger flowers. They grow best in partial to total shade. A hybrid variety, I. hybrida Bounce™, is particularly robust.

Some additional impatiens are appropriate for bright, sunny areas. The  I. hawkeri SunPatiens® series is the first impatiens developed to flourish in full sun. These plants are generally larger and bushier than other New Guinea impatiens, and produce more flowers.

The Missouri Botanical Garden offers complete descriptions of New Guinea impatiens and SunPatiens®. Many other bedding plants can also be planted in place of impatiens. See Cornell Cooperative Extension Suffolk County's Alternatives to Garden Impatiens for a list of potential substitutes, with information on each.

For tips on a variety of gardening topics, see our Plant Information Guides.

- Courtesy of NYBG Plant Information Service

  • Last Updated Aug 24, 2023
  • Views 6260
  • Answered By Plant Information

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