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Powdery mildew


Is it possible to say if powdery mildew is down to under/over watering based on the plant? I have some Salvia Crystal Blue and Verbena bon. that have it present (the former more than the latter) but as these don’t mind dry-ish conditions is it because I’ve over watered during the past few weeks?

The Salvia have had two flushes of flowers and only started to get mildew towards the end of its second flush. The new growth they’ve put on since I removed the flower spikes seem ok so far but the rest of the plants look in a sorry state (sage leaf hopper hasn’t helped). 

The verbena has it on the lowest foliage which possibly indicates that it’s due to the watering?

Our soil is quite dry and of course, the lack of rain and heat we’ve had made me think I should water them regularly but maybe I’ve watered too much or left it to late?



  • AnniDAnniD Posts: 11,909
    I always find it difficult to advise re powdery mildew as it can be difficult without actually seeing the plant in situ. A lot depends on your type of soil, and the extreme weather we had a couple of weeks ago is only making its results known now in some cases.

    Mt insinct with regards to the salvia is to cut it right back to the ground, give it a good drink (at least half a watering can, possibly more), and wait for fresh growth. 
    With the Verbena Bon, l would spray the affected leaves with something like "Fungus Fighter". Get a trowel and just dig down around the roots to see how damp it is further down. This should help guide your watering. 

    Others may have different advice,  that's the joy of gardening  :)
  • B3B3 Posts: 26,421

    Some of my VB gets mildew this time of year. I just cut it back to just above the lowest set of side shoots and fresh growth will develop.
    In London. Keen but lazy.
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