Fertilizing houseplants


Hi there. I have both Miracle-Gro shake n feed as well as the regular all-purpose water-soluble fertilizer. Is it possible to use this fertilizer on my houseplants? They include pothos, ficus elastica, dracaena marginata, spathiphyllum, and sansevieria. Thanks in advance!


Thank you for contacting the Toronto Master Gardeners.

All plants require certain essential elements for proper growth. Unlike an outdoor garden, where nature provides rain and plants can send new roots searching for food, the nutrients available to a houseplant are strictly limited by the amount and type of soil that is in the pot and whatever else you give it as a supplement.

The packaging on your fertilizer containers will likely show three numbers eg. 10-10-10 or 8-9-12 etc. The first number, (N) nitrogen, primarily enriches the “greenness” of the foliage and promotes stem and leaf growth.  The second number, (P) phosphorus, encourages flowering, fruiting and root growth. The third number, (K) potassium, is for overall plant health. It contributes to stem strength, root growth and disease resistance.

Plant food which is formulated for flowering plants  usually contain less nitrogen and more phosphorous and potassium. Those fertilizers designed for foliage plants tend to to have higher nitrogen content.

Fertilizers come in several different varieties: liquid, sticks, tablets, granular, and slow-release forms. Slow-release formulas are generally designed for a single yearly application and last for 6-9 months under normal growing requirements. Liquid/ water soluble are convenient because the dilute solutions reduce the potential for fertilizer burn. Granular fertilizers are designed for outdoor use. It is also important to remember to always follow the instructions on your fertilizer as to the dilution factor. Too much fertilizer can kill a plant, scorch its leaves or lead to salt build up in the soil. Too much fertilizer is often worse than not enough.

Not knowing the specifics of your fertilizer (% of N-P-K) it is difficult for me to give you an answer as to whether they are suitable for your houseplants.

Ideally, plant food specifically designed for feeding indoor plants, which are grown for foliage, (which appears to be your case) should have a higher first number – that is, more (N) nitrogen.  A balanced plant food with equal amounts of (N) nitrogen, (P) phosphorous and (K) potassium, would also be a good choice.

When to feed houseplants is determined by the plant’s growth rate, age and season. You should avoid feeding your plant when it is under stress or during periods of inactive growth ( October – March). Begin feeding your plants in the spring  (March-September) and summer when day length and sunlight intensity increases.

You may wish to read: Beginner’s Guide to Growing Houseplants: A Toronto Master Gardeners Guide

For another useful article, click here.