Place a Tablespoon on Any Plant at Home: What to Expect

1. Epsom Salt (Magnesium Sulfate)

• What happens: If diluted in water first, it supplies magnesium and sulfur. Plants suffering from a true magnesium deficiency (yellowing between leaf veins while veins stay green) may perk up and darken.
• The risk: Placing a dry tablespoon directly onto houseplant soil can cause chemical burn to the roots or salt buildup, which disrupts water uptake.
• Safe method: Dissolve 1 tablespoon in 1 gallon of water and use it as a light soil drench once a month max.

2. Coffee Grounds

• What happens: Coffee grounds add mild organic nitrogen and improve soil structure slightly as they break down.
• The risk: A solid layer of dry grounds placed on top of indoor soil creates a dense, hydrophobic crust that prevents water from reaching the roots. It can also trap excess moisture underneath, causing stem or root rot and attracting fungus gnats.
• Safe method: Mix no more than a light sprinkle into the top inch of soil, or compost them first.

3. Crushed Eggshells

• What happens: Adds calcium to the soil.
• The risk: Raw eggshells take months or years to break down in potting soil. Dropping a tablespoon on a houseplant does virtually nothing in the short term and can attract pests or mold if not washed properly.
• Safe method: Boil and finely powder the eggshells in a blender before working them into outdoor garden soil, or use a liquid calcium additive for indoor plants.

4. Table Salt (Sodium Chloride) or Sugar

• What happens:
  • Table Salt: Will dehydrate and kill the plant. Sodium draws water out of the root system through osmosis.
  • Sugar: Causes a massive spike in soil bacteria and mold, throwing off root health and attracting ants or fruit flies.
• Safe method: Keep both away from houseplant soil entirely.

Summary Checklist for Indoor Plants