Tips for Fertilizing Houseplants

My Garden Life
December 15, 2021
Table of Contents
Compared to plants growing outdoors in a natural ecosystem, houseplants need to work with more limited resources. Indoor plants soon use up the essential nutrients in their soil, and these will need replacing for the plant to thrive. You can do this easily using fertilizer, but the topic can be a little confusing when you first start out. Here are the answers to some of the most common feeding questions, to help you keep your houseplants happy and healthy.

Feed Your Houseplants in Spring and Summer

close up of schefflera plant foliage yellowing with signs of nutrient deficiency

Plants need a combination of nutrients, light and water to grow. It stands to reason they’ll need more of these resources when they’re growing most strongly. Houseplants usually need more feeding in spring and summer, when most species are growing, than in winter when growth slows or even stops. If you notice foliage discoloring, and you’ve ruled out other factors such as light, water or temperature, then it’s possible that your plant is developing a nutrient deficiency.
In particular, flowering plants need increased feeding just as the buds form, to give them the energy they need to bloom. In most cases, you should stop feeding plants a week or two before they start to slow down for winter.

Use Liquid, Slow-release or Granular Fertilizer for Houseplants

composite image showing different types of houseplant fertilizer, liquid, stick, and granulated

Fertilizer is available in a wide variety of forms, including liquid, powder, granules, tablets, slow-release and more. For houseplant use, the two most suitable are liquid and slow-release feed.
  • Liquid fertilizers are diluted in water to the correct strength and applied directly to the soil. They’re quickly absorbed, and it’s easy to control the amount to match your plant’s needs.
  • Slow-release fertilizers take the opposite approach. Usually sold in stick, tablet or pellet form, they’re made with different layers of materials which decay at different rates, gradually releasing nutrients as they go. Slow-release plant feeds are simple to use. Each fertilizer application can gently feed your plants for months.
  • One last form that’s often used for houseplants is granular fertilizer. These small pellets can be mixed into potting soil or sprinkled on the surface. They quickly dissolve when the plant is watered. Granules are an inexpensive way to refresh spent soil, but their almost immediate action means precise control is difficult, so for houseplants they should be used with care.

Organic vs. Non-organic Fertilizer for Indoor Plants

hand scooping organic fertilizer into the pot of a spider plant

Organic fertilizers are derived from animal or plant sources, such as bone meal, pelleted manure or seaweed. Non-organic fertilizers are made synthetically, often as byproducts of the chemical or mining industries. Both types have their uses.
Organic fertilizers tend to release their nutrients more slowly, giving your plants benefits over a longer period. Non-organic fertilizers usually provide the nutrients in a form that’s quicker to absorb, making them suitable for giving plants a quick boost or to correct a nutrient deficiency.

How to Feed Plants at Half Normal Rate

hand pouring liquid fertilizer mixed at half-strength into a vase of rooting pothos cuttings

Some plant labels specify feeding at half the normal rate. This means using a liquid feed diluted to half the usual strength, or using half the amount of granular fertilizer, rather than feeding less often. This is particularly important for plants like pothos grown in water, where nutrients are more easily absorbed, and too high a concentration will be counterproductive.

Overfeeding Scorches Houseplants

cactus in a clay pot with salt residues forming on the lip of the pot

More isn’t usually better when it comes to feeding houseplants. In the confines of the pot, any fertilizer that the plant doesn’t need will build up rather than washing away naturally as it would outdoors. If the nutrient levels get too high, they can ‘scorch’ the plant’s roots, stunting its growth or even killing it.
White residue accumulating on the rim of the pot can be a sign that there is an excess of fertilizer building up, or this can also indicate hard water. Always follow the recommended feeding amounts, erring on the side of caution rather than assuming your plants will appreciate a little more than the label says.

Using Kitchen Scraps to Fertilize Houseplants

hand placing crushed egg shells on the soil surface of a potted plant

Reducing waste is always a good thing, and many people like to add certain kitchen scraps to their houseplants’ pots rather than throwing them away. For example, clean eggshells crumbled onto the compost will eventually break down to provide calcium while helping to retain moisture in the meantime.
But, adding other items such as banana peel may not be quite so advisable. While they’ll provide valuable nutrients, they’ll also attract fruit flies or even rodents, and will produce an unpleasant odor as they decompose. If you want to make better use of scraps, try boiling them first to make a tea, and use this as a homemade liquid fertilizer.

When to Buy Specialist Houseplant Fertilizers

close up of flowering violet plant with pot of mixed cacti in the background

In most garden stores you’ll see fertilizers formulated for specific plant species, or for groups such as flowers, herbs and vegetables. These products have a mix of nutrients balanced toward those plants’ needs and can bring better results. For example, plants with large flowers will need a greater proportion of phosphorous in the mix, while ones with lush leaves will prefer more nitrogen.
If you’re a fan of growing a particular range of plants, then specialist fertilizers can be useful. But a general purpose, well-balanced feed is fine for most houseplants.
Fertilizing houseplants is important, but it’s not the only factor in successful growing. We’ve got expert advice on light and water for houseplants to keep your plants healthy.
row of a beautiful variety of potted houseplants on a table lining a wall with plant paintings

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