University of Maryland Extension

Mineral and Fertilizer Salt Deposits - Houseplants

mineral orchid

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Mineral and fertilizer salt deposits usually appear as white crystallized coatings on plant leaves or as a white crust on the surface of the growing media or pot. Mineral salt deposits are caused by the use of hard water that has high concentrations of dissolved substances such as calcium carbonate, sodium, and iron. Fertilizer salt deposits are the result of the various components of soluble fertilizers. Both kinds of salt deposits can cause harm to plants by competing for the available moisture and causing desiccation or "burning" of tissues. In addition, these deposits can affect the pH of the growing media as well as block absorption of essential plant nutrients.

Management: To prevent mineral salt deposits use a good water source low in dissolved minerals. To prevent fertilizer salt deposits follow the manufacturer's application instructions and wash off any spills on plant surfaces. In both cases, avoid bottom watering or pots without drain holes and flush the growing media from the top with several volumes of pure water. In severe cases, repot with fresh potting media.

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