Potted plants - white powdery mildew

emily_0.6 · October 2018

Hello! I am having an issue with white powdery mildew in the garden at the moment. Currently renting with a patio so all my plants are in large pots/planters. Seemed to start on my hydrangeas (mop heads and paniculata), but is now affecting dahlias, the last of the sweet peas and salvias.

They were all originally potted in multipurpose compost unfortunately and drainage isn't very good and if anything the roots seem too wet. Have re-potted with a compost/grit mix to improve drainage and spread them out to hopefully improve air flow.

I'd be grateful if anyone had any suggestions as it seems everything I've read suggests powdery mildew seems to be a product of dry roots!

I've cut off the affected leaves/stems etc. so hoping things will improve...

Thanks!

Obelixx · October 2018

Powdery mildew is often a response to stress from heat and drought. Good move to use better quality compost for your pots. I reckon multi-purpose is fit only for spreading on beds as a mulch or soil improver.

Do make sure they get regular watering and feeding thru the growing season as planting composts only have food for 90 days max. You need to top dress with a good, slow release fertiliser every spring and add top ups or liquid feed thru the growing season so the plants stay healthy.

For now, you could give a handful of bonemeal to each pot to improve plant health over winter without encouraging soft, sappy growth that will be damaged over winter. Keep on removing affected foliage and destroy it. Do not compost it.

Bee witched · October 2018

Hi Emily,

You could try 5g bicarbonate of soda in 1L of water - add a dash of washing up liquid to the mix to help it stick – and spray your plants on a dull day when there is no rain forecast.

Cheap to do and has worked for me.

Bee x

emily_0.6 · October 2018

Thanks both! I will give these tips a go, hoping with the weather at the moment air flow will definitely be improved

Potted plants - white powdery mildew

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