How to Fertilize Houseplants: Timing and Strength for 10

Of the 10 houseplants we cover, seven have a feeding schedule from an extension source, and they run from every two weeks to once or twice a year. Monstera sits at the frequent end and ZZ plant at the rare end. Fiddle leaf fig has only a columnist’s personal routine, and aloe vera and rubber plant have no feeding guidance in our sources at all.

Feeding schedule for each plant

Sources give strength as a fraction of the label dose, such as half strength or one-quarter strength. The only ratios named are 20-20-20 (Clemson, peace lily) and 3-1-2 (a Penn State columnist, fiddle leaf fig). No source names a brand or product, and neither do we.

Where sources disagree

Peace lily. Clemson says: “use a balanced, liquid houseplant fertilizer, such as 20-20-20, every six to eight weeks during the spring and summer growing season,” mixed at “one-quarter of the recommended strength.” UF/IFAS EDIS says: “Apply a low dose of liquid fertilizer according to manufacturer instructions three times per year.” Clemson feeds more often, and EDIS gives no strength.

ZZ plant. This is the widest split. NC State says: “Use a balanced liquid houseplant fertilizer once or twice a year.” UF/IFAS EDIS also says twice a year. Clemson says “once or twice during the growing season.” Illinois Extension says: “Provide a light supply of balanced fertilizer once or twice a month at the time of watering during the spring and summer months.” The first three agree on once or twice per year or season, and Illinois alone says per month. Clemson’s reason is that ZZ plants are “slow-growing.”

Pothos. NC State says: “Fertilize every other month except when the plant is dormant in the winter.” Wisconsin says the same, “except during the winter when the plant is not actively growing.” Clemson says every other month in spring and summer. Penn State says: “fertilize pothos with a balanced houseplant food monthly through the winter and every two weeks throughout the rest of the year.” That is the only source that feeds in winter, and it feeds more often than the others at every other time.

Monstera. Penn State: “Fertilize every two weeks through the growing season and monthly through the winter.” Wisconsin: “Fertilize regularly from spring until fall,” with no interval and no winter feeding. They agree on the growing season but not on winter.

Fiddle leaf fig. The Penn State source is an Extension county news column, not a research rate. The writer says: “When I am ready to water, I infuse the gallon of water with a tablespoon of a liquid fertilizer that has a ratio of 3-1-2.” Treat it as one grower’s routine. Our sources give no extension rate for this plant.

Seasons: when sources say to hold back

• Pothos: skip winter, when it is dormant (NC State, Wisconsin), apart from Penn State’s winter schedule above.
• Calathea: NC State’s majestic prayer plant page says to “Reduce watering and fertilization in the winter when plant growth typically slows down.”
• Snake plant, peace lily, spider plant, calathea: sources tie feeding to the growing season or active growth. Our reading is that this means no feeding outside it.
• Rubber plant: NC State says to reduce watering when dormant, from fall to late winter, and says nothing about feeding.

Our sources do not say whether to feed a plant that is newly repotted, stressed or recovering. For pot and mix, see repotting houseplants.

What too much fertilizer does

• Peace lily: “Overfertilizing peace lilies can cause the leaf tips and roots to burn and turn brown” (Clemson).
• Spider plant: “Do not over-fertilize, as this decreases plantlet formation” (NC State). Wisconsin adds that heavily fertilized plants “may not form as many plantlets and excessive fertilizer may lead to tip browning.” Clemson says leaf tip burn is caused by “too much fertilizer or water that is high in soluble salts.”
• Pothos: blackened leaf margins or tips “can be caused by overwatering, inadequate watering, or excess fertilizer” (Wisconsin).

Brown tips therefore do not prove a feeding problem. Humidity for houseplants and how often to water houseplants cover the other causes.

Short version

Most sources tie feeding to the growing season. They span monthly for snake plant and calathea, every two weeks for monstera, and once or twice a year for ZZ plant. Pothos skips winter in two sources, Clemson names spring and summer, and Penn State feeds through winter. Aloe vera and rubber plant have no stated schedule, and fiddle leaf fig has only one columnist’s routine. For easy plants to start with, see easy houseplants.