Soft & Downey & Deadly to Impatiens

Hello Peter, Thanks for the information on upcoming seedlings. My query is this. For a few years now I have avoided growing Impatiens due to rotting when they seemed to be doing so well. Has this problem been eliminated or will I still be taking a risk trying again. I always had such pleasure over the summer months watching my colourful friends keeping "busy"

Looking forward to seeing my garden full of Busy Lizzies again, thank you from Kay.

What a timely question. Careful Peter, timely in time of year, not that we have seen any sign of the dreaded Impatiens Downey Mildew. In fact we are growing beautiful Impatiens this year.


So beautiful in fact we are treating this tray (Summer Berries and about 30 of her friends) as not up to our standards but that's just because she's too big to offer shelf life in a retail garden centre.

I have written about Impatiens Downey Mildew previously, so you can find lots of information here. Unfortunately I can't say the Downey Mildew has gone away or that we have found a miracle cure.  We are being careful not to bring any Impatiens plants into our nursery and we grow our seedlings very 'dry' which prevents the fungi spores germinating.

There was a research program done some years back (Wow 1996) on Downey Mildew in Brassica Vegetable seedlings, a closely related but different strain.  Both diseases have similar symptoms to each other but they are very specific to the host plant, they are not interchangable. The recommendation of this research was to NOT water our plants between 9.00 & 11.00am. This is the time when the spores are most active and the addition of water just provides a perfect environment for germination. I favour 'early' watering to ensure time for evaporation through the day. Water sitting on foliage over night is just bad news as it encourages any number of fungal & bacterial diseases.

Unfortunately the other critical cultural element is to remove any diseased plant material and ensure that Impatiens are not grown in the same space again at least for a season or two. This is of course the ancient crop rotation system. Sad really, I clearly recall cousin Fred Wood lamenting that Impatiens seedlings would last so long that they had ruined the autumn flower seedling sales season... perhaps there's a conspiracy! Anyway, if Kay hasn't grown Impatiens for a few years she is a good chance to make a fresh start so long as she chooses 'clean' seedlings. This applies to potted plants as well, If you find the disease don't fight it. Remove the infected stock and clean containers thoroughly with disinfectant.

Actually, the best advice I can offer is to grow New Guinea Impatiens.  The Impatiens Downey Mildew disease is so specific that it doesn't even effect this close relative of Impatiens wallerana.

Wicking Gardens

Some times I wonder if writing a weekly newsletter is a wise use of my time. I enjoy the variety but there's no measurable return on my investment. And then I get some gems!  Direct communication with gardeners and garden retailers produces an idea or challenge every now and then that I am sure would never otherwise come up.  I received this enquiry:

hi there,
just looked over your website. keen on purchasing a few of them (Magic Square Gardens), delivered and fully planted ... weighing up cost considerations BUT also ... wondering if you're able to set up a wicking bed system in them?? ...
look forwarding to hearing from you.
Cheers,
Aj.  (Aj's website is worth a look, PD)



Wicking beds!  I hadn't even heard of wicking beds until 12 months ago when the Chelsea Heights Earth Carers asked for some plants to fill their one built into an old trailer.  The concept is simple, very effective and used extensively in the horticulture industry.  In its simplest form the wicking bed is going on a holiday and leaving your pot plants sitting on one end of a towel with the other end in a bucket of water or the bath. "Capillary action" draws the water up the towel to the pot plants. The growing media in the pot draws water up into the root zone by the same process.

Potted plant growers have been playing with this process for years now and there are many systems in use through the industry, some of them very technically advanced. The horticultural benefits are the reductions in water and nutrient use plus reduced disease risk because the foliage remains drier. The environmental benefits are obvious.

Take a look at Colin Austin's web site for details on wicking beds.  I have researched the wicking concept enough (asked the Earth Carers about their set up) to have decided that it suits our Magic Square Gardens perfectly and provides a passive water management option that sits comfortably beside the active, solar pump version offered by Waterwand.  Waterwand will hold significantly more water as it's clever reservoir is an open space as distinct to the sand filled bed used for wicking gardens.  

I'm keen to get feedback from anyone who has used a wicking bed system.  Please let me know why they are great, or otherwise.  I have to get cracking and put something together for Aj.