Fertilizer For Indoor Plants | University Of Maryland Extension

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Updated: March 10, 2023

How to manage the nutrient needs of houseplants

The goal of fertilizing indoor plants is to add just enough nutrients so that the new growth compensates for leaf loss. The purpose should not be to encourage quick growth of a large plant. Large amounts of fertilizer are therefore unnecessary for most indoor plants.

• Fertilizers come in many different forms; liquid, granular or tablet.
• Slow-release pellets which release over a period of 3-4 months are also available. They can be incorporated into the potting soil when planting or applied to the surface.
• Commercially available fertilizers labeled for indoor plants or houseplants are fine, mix according to label directions. Many will give you a choice of concentrations depending on whether you prefer to fertilize once a month or at each watering.

Remember the following points when trying to balance your indoor plant's nutrients:

• Micronutrients are deficient in many indoor plants, so replace them once a year. Fertilizing with a commercial fertilizer labeled for indoor plants which contain micronutrients or adding a small amount of well-composted, screened leaf mold or other compost will fill this need.
• Because magnesium leaches from the soil at each watering, replace it with a solution of one teaspoon Epsom salts per gallon of water. Water two times each year or use the solution as a leaf spray;
• During the winter months, indoor plants don’t need fertilizer because reduced light and temperature result in reduced growth. Fertilizing at this time could harm some plants. Fertilize from March through September;
• Monthly applications of a diluted liquid fertilizer in the summer months will keep most plants healthy; earthworm castings are an excellent houseplant fertilizer; and
• Excessive fertilizer results in the buildup of salts and excessive, leggy growth.