While sunlight and water give our favorite green homebodies the basics to survive, they need some essential macronutrients to truly bloom. Whether it’s time to bring your plants inside for winter or it's the height of summer, fertilizer is our plants’ best friend (next to us, of course). It can mean the difference between sad, droopy leaves and green-for-all-seasons growth.
In this comprehensive guide to plant fertilizers, we’ll show you fertilizer types, enriching nutrients to look for, and how to fertilize live indoor house plants to keep your garden lush, no matter the season.
Why Should You Fertilize Indoor Plants?
While it’s important to start with good, fertile potting soil, the nutrients in your potting mix only lasts for so long. As plants absorb these nutrients through their roots, the amount of nutrients available depletes. Many of the nutrients can be filtered out during watering, which may result in a deficiency if they aren’t replenished.
Unlike outdoor plants, which get the nutrients they need from their symbiotic relationship with nature, indoor plants spend their lives in pots. Maintaining adequate nutrient levels with regular fertilizer feedings ensures they get the nourishment they need to encourage strong, vigorous growth and disease resistance.
How To Fertilize Indoor Plants
Not all plant food is the same, so sometimes finding the right fertilizer for your indoor plants can feel like choosing meals off a menu without knowing the ingredients or how it's prepared. For instance, is your anthurium in the mood for seafood? Does your philodendron feel like having a three-course meal?
Here’s how to differentiate fertilizers so you can confidently give your indoor plants the best plant food for their unique needs.
Types Of Fertilizer
Choosing the best fertilizer for indoor plant starts with familiarizing yourself with the different houseplant fertilizer types:
- Liquid fertilizer – Liquid plant food like Miracle-Gro® Water Soluble All Purpose Plant Food is the quickest way to get nutrients to your plants. It comes in powder or liquid form, is diluted in your watering can, and is fed to plants as part of their regular watering schedule. Liquid fertilizer is typically given every 1 to 2 weeks. Its ability to deliver nutrition fast makes it a superb choice for fast-growing plants that require lots of energy.
- Granular fertilizer – Miracle-Gro® Shake 'N Feed All Purpose Plant Food and other granular fertilizers usually come in the form of small pellets. These are sprinkled or mixed into the soil, gradually releasing nutrients with each watering. When you’re transferring your pilea to a bigger pot, mixing granular fertilizer into the potting soil mix will keep its shiny green saucers flying high.
- Slow-release fertilizer – Extended-release fertilizers like Miracle-Gro® Indoor Plant Food Spikes are often found in tablet or stick form and provide a steady stream of nutrients for months rather than a one-time influx. Since these work well in smaller pots as the nutrients can take some time to disseminate, try using them to give extra nourishment to an easy-going peperomia.
Foliar fertilizer – Foliar feeding is another way to keep your houseplants looking their loveliest. While most fertilizer feeds plants through the plant roots, foliar fertilizer is administered by spraying their leaves and around the root base.Humidity-loving tropical plants like monsteras and calatheas enjoy a nice misting to feel their best, so including a little fertilizer for a few of their spritz baths will nurture their lush, beautiful leaves.
Whichever fertilizer type suits your plants best, be sure to read the packaging instructions before integrating it into their care routine. Every fertilizer has its own formulation and recommendations for quantity and feeding frequency.
Organic vs. Synthetic Fertilizers
In addition to how they’re delivered, fertilizers can also be classified as organic and inorganic. These differ based on how they’re made and the way they distribute their nutrients:
- Inorganic or synthetic fertilizer is a manufactured, water-soluble plant food that provides a rapid delivery of balanced nutrients to plants.
- Organic fertilizer, like fish emulsion, is carbon-based and made from living organisms. It feeds the soil rather than the plant, which means it’ll take longer for the plant to receive the nutritional benefits.
Essential Nutrients For Plant Health
When purchasing plant food, you’ll notice an NPK ratio listed on the package, like 10-10-10 or 18-18-21. This refers to the proportion of 3 chemicals—Nitrogen (N), Phosphorus (P), and Potassium (K)—each of which performs specific functions to meet your plant’s needs:
- Nitrogen stimulates leaf development
Phosphorus promotes strong plant roots and lively blooms
- Potassium encourages stem growth and disease resistance
A well-balanced fertilizer will contain almost equal amounts of each of these main macronutrients. You can also feed your plant with sources that have higher levels of certain elements; for example, a flowering plant may need more phosphorus than a plant that’s foliage-only.
Fertilizer also contains other secondary macronutrients and micronutrients that can boost plant growth, including:
While quantities of each nutrient will vary depending on the houseplant fertilizer you use, you can also feed your plants by taking a nutrient-specific approach. Some indoor gardeners supplement plants’ fertilization regimen with an occasional Epsom salt feeding, which provides extra magnesium and sulfur to encourage plant vigor.
Tips For Buying Fertilizer
When deciding on the best fertilizer for indoor plants, there are a few things to keep in mind:
- Plant type – Fertilizers are formulated to provide the ideal nutrients for a growing plant, but different types of plants have different nutritional needs. For many houseplants, a general indoor house plant fertilizer will work just fine, but you’ll want to look for variety-specific food for plants like orchids, African violets, and succulents.
- Container type – The pot that your houseplant lives in could also influence the type of fertilizer you choose. You might want to consider a granular or extended-release fertilizer for a hanging basket. On the other hand, a large or fast-growing floor plant in a heavy planter might fare better with a liquid fertilizer that delivers nutrients quickly.
- Feeding frequency – If you’re a pro at sticking with your watering and feeding schedules, a liquid fertilizer could work well for you. If you tend to take a more relaxed approach to plant care, you may prefer a slow-release fertilizer since they slowly give nutrients to plants for months before you’ll need to replenish them. Consider how consistent you are with watering and feeding, and choose accordingly.
When To Fertilize Your Indoor Plants
Even though they’re living the good life in your warm, cozy home, most houseplants still adhere to a seasonal growth schedule. So, how do you know how often to fertilize indoor plants?
In general, your indoor plants should be fed during periods of active growth. They need a boost when they’re putting extra energy into unfurling those little baby leaves or flowering stalks. As days get shorter and the weather cools, most houseplants will quiet their growth schedule and won’t need much more than occasional watering.
The type of fertilizer you select will help you determine a proper feeding frequency as well. Again, follow your chosen fertilizer’s instructions to determine the optimal amount and frequency of feeding.
Signs Of Overfeeding
If you notice any of these symptoms of fertilizer burn in your houseplants, you may be nurturing your indoor plants a little too much:
- Yellowing leaves
Lack of blooms in flowering plants
Loss of leaves
- Crust on the surface of the soil
When this happens, try diluting your fertilizer or lengthening the time between feedings. Remember, it’s important to account for the added nutrients from your potting mix when determining when and how much fertilizer to give your plants. Some potting soil, like Miracle-Gro® Indoor Potting Mix, contains slow-release fertilizers that can feed for up to 6 months (which means extra fertilization isn’t necessary right away).
Fertilizing Indoor Plants vs. Fertilizing Outdoor Plants
Indoor potted plants have different needs than outdoor landscape plants due to their growing environment.
In an outdoor environment, plants have more room to spread their roots and seek out nutrients and water. Depending on the type of plant, they generally need to be fertilized twice: once at the beginning of the growing season and once mid-summer.
Indoor plants, however, are restricted to the pots or planters we place them in. This limits their ability to access energy sources, which means they may need to be fed more frequently.
Keep Your Indoor Plants Well-Fed With Greendigs
Indoor plants connect us to the natural world, calm our senses, and can purify the air in our homes. And just as we humans rely on balanced diets (or our favorite gummy vitamins) to maintain optimal health, our plants depend on us to nourish them with a medley of essential nutrients.
Greendigs online plant store has everything you need to help you grow what you love. Our selection of soil & food will keep every plant in your home happy and well-fed throughout the growing season, so they can flourish year-round.
When you’re ready to expand your foliage family, explore our extensive collection of live indoor house plants to style your space into a lush, serene oasis you’ll never want to leave.
University of Minnesota Extension. Quick guide to fertilizing plants.
Garden Guides. Plant Fertilizer Deficiency Signs.
HGTV. Fertilizing Houseplants 101 (Plus, How to Make Inexpensive Homemade Fertilizers).
University of Maryland Extension. Fertilizer for Indoor Plants.
University of Minnesota Extension. Quick guide to fertilizing plants.