All About Fertilizing Houseplants

Even for storied plant-lovers, fertilizing can be a challenge. While mastering the life-giving forces of water and light are always the first and best priority, understanding just how to supply your plants with the nutrients they need is tremendously important to their long-term health. 

But where to begin? What kind of fertilizer should you use, and how often? Do your plants even need fertilizer? What about compost? These are all very valid questions which we hope to answer here!

What does fertilizer do? 

When growing outdoors, plants are plugged into nature’s incredibly complex nutrient cycle. They receive nutrients from the rain, from the constantly shifting contents of the soil, packed with compost, humus, worms, and so on. When moved inside, their access to these life-sustaining nutrients obviously decreases—and that’s where fertilizers come in. 

While we may colloquially refer to fertilizers as ‘plant food,’ they aren’t actually food. Through photosynthesis, plants produce all of their own food and energy. But fertilizers can supply your plants with a lasting supply of the nutrients they need, specifically Nitrogen, which promotes foliage growth, Phosphorous, which promotes flowering, and Potassium, which promotes healthy roots. Most modern potting mixes include fertilizers, but it can take as little as two months for these nutrients to be used up, meaning your plants are in need of some vitamins.

Types of Fertilizer 

There are lots of different kinds of fertilizer, as you probably know if you’ve ever tried shopping for one at your local nursery. The most common types of fertilizer are granular, liquid, and slow-release. These can come in either chemical or organic varieties. 

We recommend an organic liquid fertilizer for indoor use, because they are easiest to regulate and the safest for indoor spaces. There are many brands to choose from, including small-batch artisan fertilizers which are becoming more popular and accessible.

With a liquid fertilizer, you have the ability to increase or decrease the concentration, depending on a specific plant’s needs. Another great thing about liquid fertilizer is that you don’t have to add a separate step to your plant routine, because fertilizing happens as you water! 

When choosing a fertilizer, pay attention to the NPK—the concentration of Nitrogen, Phosphorous, and Potassium. Not all fertilizers will feature this acronym, but it is commonly denoted as a set of three numbers, which describe the fertilizer’s ratio of those ingredients. For instance, 10-10-5 means that the fertilizer contains 10% Nitrogen, 10% Phosphorous, and 5% Potassium. This is important if you are growing plants like orchids, or African violets, because they will have specific nutrient needs that are unlike most other houseplants.

When to Fertilize 

Much like light and water, different plants have different fertilizer needs, both in terms of frequency and concentration. As always, it’s best to research the plant species in your home to determine how to care for each of them. Fortunately, though, most plants have similar enough fertilizer needs that you can easily set them up on a regular schedule. 

When creating a fertilizing schedule, always check the instructions on the fertilizer packaging first. Some fertilizers will recommend a frequency of use, and it’s usually best to follow the package instructions, especially when calculating the ratio of fertilizer to water, as too much fertilizer can actually hurt your plant. 

Most liquid fertilizers recommend that you fertilize every other time you water—whether that’s once every other week in the summer, or once every month in the winter. This way you aren’t overwhelming your plants or letting the nutrients in your fertilizer go unused.

Remember that your plants will need less fertilizer in the slow-growth winter months, and will likely start wanting more in the spring, when they begin storing up energy for new growth.

Fertilizer vs. Compost 

So what’s the difference between fertilizer and compost? While both can be highly beneficial to your plants’ overall health, they don’t quite perform the same function. According to the gardening experts over at Bonnie Plants, “compost feeds the soil and fertilizer feeds the plants.” Compost helps maintain the ‘soil food web,’ a complex chain of microbial and fungal life that keeps soil healthy, which produces ideal conditions for plant roots to grow in. While composting can provide your plants with some necessary nutrients, pairing it with an organic fertilizer is the best way to keep both your soil and your plant healthy and thriving.

Key Takeaways 

  • Fertilizing is a necessary piece of plant parenting 
  • Fertilizing isn’t food, but a vitamin 
  • The key ingredients in fertilizer are Nitrogen, Phosphorous, and Potassium
  • Be sure to check the NPK of a new fertilizer before buying it 
  • Organic fertilizers are best 
  • You can build fertilizer into your watering routine 
  • Don’t overdo it—follow the instructions on the package
  • Compost isn’t the same as fertilizer, but they can be used together 

Thanks for reading! I hope that next time you visit your local gardening center or plant store, you feel more confident in choosing the right option for you and your plants. Share your journey with us @houseofplantlovers and as always, happy growing!

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