How to fertilize houseplants
When to feed, how much, and when to stop
Why houseplants need feeding
Potting mix holds very few nutrients, and watering slowly washes them out. Light, regular feeding replaces them, but houseplants grow slowly and don't need much.
Fertilizer can't make up for poor light or watering. It only helps a plant that's growing well already, and plants in dim light need very little.
When and how often
Feed only while plants are actively growing, usually from about March to September or October. A liquid houseplant fertilizer about once a month is plenty for most plants; all-purpose products are often used at half strength.
The goal is steady, healthy growth, not a fast, oversized plant. Large amounts of fertilizer are never needed indoors.
In late fall and winter, when growth slows, stop feeding until spring. Slow-release pellets that last 3 to 4 months are an easy alternative to liquid feeds.
How to feed
A few rules keep roots safe.
- Water first if the potting mix is dry. Never apply fertilizer to dry mix.
- Use the label rate or less. More is not better.
- For foliage plants, a balanced feed such as 20-20-20 works well.
- For flowering plants, a feed higher in phosphorus, such as 15-30-15, is often used.
- Pick one labeled for houseplants that includes micronutrients, which indoor plants often lack.
When not to feed
Skip it in these cases.
- New plants: they usually come with enough fertilizer for 2 to 3 months.
- Freshly repotted plants, for the first few weeks.
- Sick, injured or stressed plants. Fertilizer isn't medicine; fix the problem first.
- Plants that are resting for the winter.
Reading the signs
Too little food shows as pale or yellowing leaves and poor growth. Yellow leaves with green veins often point to a shortage of iron.
Too much shows as a white crust on the soil or pot, brown leaf tips and edges, dropping lower leaves, wilting, or lots of weak, lanky growth. If you've overdone it, run plenty of clear water through the pot and let it drain, several times.
Related plant problems
Sources
- NC State Extension: How to Fertilize House Plants
- University of Maryland Extension: Fertilizer for Indoor Plants
- Iowa State University Extension: How to Care for Houseplants
- Clemson HGIC: Indoor Plants: Cleaning, Fertilizing, Containers & Light Requirements
General guidance, not a diagnosis. Written by PlantWiz in our own words from the sources above.