Question
I purchased an orchid recently and noticed that a white substance (sort of like powder) developed on the outside of the pot.  The pot is a terracotta pot.  I water the orchid regularly, about 2-3 times a week and the plant itself is healthy and there is nothing on the soil either.  
Is this white substance mold? It is harmful to the plant or humans?
Thank you!

Answer
Hi Chloe,

If the white stuff feels slimy, then it is mold. If it is dry and powdery or flaky, then it is mineral salts that are leaching through the pot and collecting on the outside.

If it is mold, then wipe it off with a solution of baking powder and water, reduce your watering frequency and try to increase the air circulation around the Orchid.

If it is mineral salts, then scrub it off with a damp scouring pad (no detergent!), reduce the watering frequency, use distilled or filtered water if your tap water is hard, and stop fertilizing if you have been doing that.

There are very few Orchids that need more than a once weekly watering. If you need further help with care for your Orchid, email a photo to my address below so I can see which Orchid species you have.

Please let me know if any of this is unclear or if you have any additional questions.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]