Impatiens Downy Mildew

posted in: Gardening | 9
Pink and white busy lizzy Impatiens walleriana

Updated information on Impatiens Downy Mildew for 2015 onwards!  Busy Lizzy bedding plants are back on sale in reputable garden centres in the UK.  So far the plants are showing no signs of the mildew and it looks as if we can have our favourite little bedding plants back on our patios again this summer!

 

For archival purposes I’m leaving the rest of this blog post on here though for now it is out of date.

 

Did you buy Busy Lizzy bedding plants a few years ago?  Did they grow well for you or did they develop a white fuzz on the underside of the leaves? Then did the leaves turn yellow, drop off and leave you with just the stems and a few unopened flower buds? Well if you were one of those unfortunate gardeners then you were not alone as the common Busy Lizzy Impatiens walleriana is in a state of crisis due to Impatiens downy mildew.

 

We all love our summer flowering plants  but I lost count of how many plants I saw develop this disease. Along with complaint after complaint from fellow gardeners.  It was due to the airborne organism Plasmopara obducens. There was nothing we could do to treat the plants. The mildew spores had finally built up resistance to the one fungicide (metalaxyl) that used to keep it under control in commercial nurseries.
Impatiens Downy Mildew was first found in the UK on the imported cutting raised plants in 2003. It then spread rapidly to the seed raised stock. So it didn’t matter where you bought your bedding plants from. Garden centre, nursery, big shed or supermarket plants all developed the mildew which remains in the soil for up to a year.  Mildews might all look the same on different plants. But each mildew pathogen is unique and this particular mildew cannot spread outside of the Impatiens family.
Impatiens Downy Mildew - Summer container full of busy lizzy Impatien walleriana
Impatiens walleriana last grown in my garden in 2010
Discussions were held with The Horticultural Development Council ( HDC), British Protected Ornamentals Association ( BPOA), and the Horticultural Trades Association ( HTA). They made an industry joint decision that this plant shouldn’t be sold in the UK for the foreseeable future.
So alas in 2012 the  common Impatien walleriana variety became be absent from most containers, borders and hanging baskets. Likewise major retailers and seed companies  joined the quest in trying to eradicate this mildew.
What might shock you is what Peter Cook told delegates at the Garden Centre Association conference in 2010 down in Oxford when he said that  it could be “a 25 year journey” to find the cure!  Just think of it – that could mean a whole generation of gardeners missing out on these colourful summer bedding plants.
Edit to add:  Now that we’re into 2014 this advice still is the same – reputable nurseries and garden centres will not be selling this plant. 

So what can we grow instead?

 

Firstly it’s only the common Busy Lizzy Impatiens walleriana that has been affected by the disease. The New Guinea ImpatiensImpatiens × hawkeri, Himalayan balsam and Impatiens glandulifera have been unaffected.
You’ll probably find that most nurseries,garden centres and online retailers will be offering a new type of impatien. It’s called DIVINE – Impatien hawkerii F1 ‘Divine mix’. The plant is highly tolerant of the downy mildew. Furthermore it has a larger flower form and better uniformity than the common impatien. Moreover it grows in shade and semi shade though can do well in sunnier conditions if kept well watered.
Impatien hawkerii F1 'Divine Lavender'
Lavender Impatien ‘Divine’  I’ll share my own photos of the flowers by the end of April….weather depending!
  • Plant 8 inches apart
  • Height  10 inches approx
  • Spread 12 inches  approx
  • Blooms all summer
  • Deep green leaves
New Guinea Impatien hawkerii F1 'Divine mix'
Impatien hawkerii F1 ‘Divine mix’  both  photos  from Panamseed.com  

Another Alternative

 

The RHS are advising gardeners to buy other plants instead of Busy Lizzies like begonias and fushias.  These are good alternatives for the problem shady areas that the Busy Lizzy once thrived in.
Finally if you do grow some Impatiens that you’ve raised as cuttings from your own plants check them weekly. If they start to show any combination of the the following signs the RHS advise that you dig them up. You can either burn or bury them deeper than 20 in (50cm) including some of the soil surrounding the plants.

Here are the signs of Impatiens Downy Mildew

  • White or grey fuzz on the underside of the leaves
  • Leaves start to curl downwards
  • Leaves start to grow in a distorted fashion and are small and pale
  • Flower buds fail to open
  • Leaves fall of plants
Were you affected by this type of mildew?

 

Rosie Nixon
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Rosie is based in Perth, Perthshire as a garden photographer, writer and nature lover. She enjoys soaking up nature in her own garden and is easily distracted from doing the weeding by anything that flutters, flies, buzzes, creeps or crawls! She enjoys sharing the beauty of creation through her photography. Rosie has been featured on TV on BBC2's The Beechgrove Garden and she uses the Scottish outdoors as her natural light studio. Her work can be seen at the only photographic gallery in Scotland - Close Gallery, 4b Howe Street, Edinburgh.

9 Responses

  1. Wife, Mother, Gardener

    So sad, but I suppose it was bound to happen to such a widely grown species. I have not heard of this occurring in the US, though I may have missed it?

    Perhaps it will open up the opprotunity for other flowers that we do not yet know very well? Plants are so opportunistic.

    Thanks for the info, Rosie!
    Julie

  2. Pam's English Garden

    Dear Rosie, Oh, dear. I hope Plasmopara obducens doesn't find its way across the Atlantic. Impatiens are an annual here — a staple of my shade-located hanging baskets. P. x

  3. The Sage Butterfly

    I live on the east coast of the USA, and I have not had this problem. And I hope I don't because I love impatiens and would really miss them. Good luck!

  4. Melanie

    Hmmn . I tried to grow these from seed but my season is so short they died in the first frost before they had even flowered. I suppose the mildew problem will force growers to diversify and grow the other plants you mention. It can only be a good thing. 🙂

  5. Andrea

    Maybe it is better to have the winter, so all the pests die also with the plants they live with. In our case, if we have the pests, they thrive continuously most of the time because our plants don't get a winter treatment. In the case of that bad 'downy mildew' on impatiens, i hope it will not be a reason for your scientists to create a GMO something to fight it.

  6. Alistair

    Yes we did have Impatiens last year and they were a complete flop, fortunately most of the area was filled with Semperflorens. I had heard of this problem, Myra felt it was because I planted them in a position which got too much sun, is this possible in Aberdeen, I dont think so.

  7. Curbstone Valley Farm

    Interesting. I used to grow the common impatiens in our first garden, as they'd reliably bloom even in partial shade. I don't think I've ever seen them suffer from anything, but admittedly I haven't planted them in a few years. I wonder if it's much of an issue here? What a shame though, they're such workhorses in the garden, which such a long bloom period, in many gardens I'd think they're indispensable.

  8. James Missier

    Its a pity the whole impatiens are now under attack and there is no cure for it.
    Hope it is not global or we all are going to loose a species just like that.

    Normally I just skip planting annuals as they die faster in my garden.

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