In the pots of dipledemia, there is regular buildup of a dry powdery buildup. I was told this is salt and can be scraped off the top. But how to prevent it? – water filtration or nutrient deficiency problem? The pot previously contained several snake plants which eventually declined/wilted due to overwatering.
Thank you for contacting the Toronto master gardeners.
The white crusty substance you see on the surface of your plants is caused by a build-up of salt from minerals in fertilizer and hard or softened water. High levels of these excess salts can prevent plants from absorbing the water they need, stunt growth and burn root tips, leading to rot. Begin by scraping the top layer of soil from the pot and discard it and replace it with fresh potting soil, or simply repot the plant if possible.
You can reduce the risk of salt build up by always watering thoroughly and pouring off excess water. Repeated and thorough watering, called leaching with tepid water will wash any remaining salts out of the soil. Water the plant thoroughly until the excess water drains out the bottom of the pot. You may have to leach weekly for several weeks to alleviate the salt build up. Never let the plant stand in the drainage water. How to Water Plants with Alkaline Water gives more information on the proper watering of your plants.
Fertilizing only when your plants are actively growing is another way you can reduce mineral and salt buildup.
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