Find Out How and When to Fertilize Your Houseplants

Adding fertilizer to indoor plants will give them nutrients to help start the growing season off right. However, too much too soon can cause more problems than going without any fertilizer at all. Here’s how to fertilize for the best results.

Once the weather begins to warm again, it’s time to transition back into gardening season. Even indoor plants are affected by the change of seasons, and the start of spring comes with special care requirements for houseplants.

Fertilizer is critical for keeping houseplants healthy. Unlike outdoor plants, houseplants are limited to the nutrients provided in the pot they live in. Restricted space means that the nutrients within potting soil quickly get depleted and need to be replaced with fertilizer.

Here’s what you need to know about fertilizing your indoor plants to give them the best head start this spring.

What’s in Houseplant Fertilizer?

Most houseplant fertilizers contain a blend of macro and micronutrients your plants need to thrive. These include nitrogen, phosphorus, and potassium (labeled as N-P-K), along with dozens of minor nutrients like calcium, iron, zinc, magnesium, and more.

The ratio between these three macronutrients will vary based on what the fertilizer is formulated for. Some blends will prioritize leaf development while others improve bud and flower formation, so choose the formulas best-suited to your plants — you may need to keep several on hand.

Types of Houseplant Fertilizer

In most cases, houseplant fertilizers come in three forms. Each has its advantages, so choose which style makes the most sense for your plants.

Liquid Houseplant Fertilizer: These fertilizers are easy to apply and come with a reduced risk of fertilizer burn. This means you can use them frequently without paying close attention to the dosage. However, they tend to soak into the soil quickly and potentially get out of reach of plant roots, which makes them less potent than other fertilizers.

Granular Houseplant Fertilizer: This fertilizer type typically comes into two styles: loose, granular pellets or compressed “spikes.” You will either sprinkle them on the soil surface or press them down into it for closer contact with plant roots. Both styles make for easy measuring so you can add precise amounts to each pot.

Slow-Release Houseplant Fertilizers: Also known as timed-release fertilizers, this type of fertilizer comes as a liquid encapsulated in a coating designed to dissolve over a long period. This lets you fertilize once and let your plants reap the benefits for weeks or even months to come. One drawback is they tend to be made from synthetic ingredients that aren’t eco-friendly.

When to Fertilize Your Houseplants

Tempting as it might be to give your houseplants some extra love during the winter, it’s a mistake to feed them fertilizer during the colder months. Colder weather and shorter days cause many varieties to go dormant (even indoors), which means they are putting all their energy into maintenance rather than growing.

Adding fertilizer during this time may break the dormancy and lead to pale, weak growth that hurts the plant more than helps it. For this reason, it’s best to give plants a break from fertilizer throughout the winter.

But, as the days get longer and the weather begins to warm again, it’s time to start a fertilization routine again.

Exception: Plants grown under grow lights year-round can be fertilized throughout the winter because they won’t experience seasonal changes in lighting or temperature.

In many growing regions, you can plan to start fertilizing houseplants about eight weeks before the last expected frost date. This gives the plants enough time to slowly ramp up production before warmer weather returns.

You’ll know that houseplants are ready for fertilizer as soon as you see signs of active growth. It’s best to think of this supplemental nutrition as a reward for growing, not as a method for stimulating it to start.

General Tips for Applying Fertilizer to Houseplants

Make sure you introduce the fertilizer slowly to not overwhelm the plants. Too much too quickly will cause more harm than skipping it altogether. So, for the first few doses, consider diluting the fertilizer to half or even a quarter of its strength. You can gradually increase the concentration over the following weeks.

Likewise, it’s best to skip fertilizing for a few weeks after repotting indoor plants. The roots will already be stressed from the shock of transplanting, so they need some time to readjust before receiving a boost of nutrients that stimulates growth.

Finally, before applying any fertilizer, make sure you read the label carefully. Failing to follow instructions will leave your plants in worse shape than if you skipped fertilizing altogether. Research what type of fertilizer is best for your specific houseplants, and follow the manufacturer’s instructions for application.

Three Other Ways to Take Care of Houseplants Before Spring

Adding fertilizer is only part of the process of helping indoor plants acclimate to breaking dormancy in the spring. Here are other steps to give them a restart for the warmer weather.

Dust and Wipe the Leaves

Houseplants can become incredibly dirty in the winter, thanks to all the time spent indoors with furnaces spreading dust through the air. Too much grime on the leaves can interfere with photosynthesis, so give the leaves the occasional wipe down with a wet rag or Q-tip to keep them clean.

This is also an excellent time to seek out signs of pests like spider mites, aphids, and mealybugs. Wipe any insects away and treat infected plants immediately with insecticidal soap to prevent infestations from spreading.

Trim and Prune

Winter dormancy makes for an ideal time to trim up indoor plants. Use pruning shears or your fingers to gently remove all dead or damaged leaves, and prune back the plant to your preferred shape. Remove any discarded plant material so it doesn’t rot in the pot and encourage mold growth or insect infestations.

Consider Repotting

Use the end of winter as an opportunity to repot houseplants that need more growing space. Make sure the pot you choose is clean and allows for drainage, and aim to disturb the roots as little as possible during the transfer process.

Fertilizer is essential for houseplants to thrive. Time your applications with the seasons, and your plants will look their best all year long.