Knowing when to fertilize your houseplants can seem like tricky business. When houseplants require more nutrients, they aren’t as communicative as when they need more water or sunlight. So how do we know when to use fertilizer?

The best solution to keep your plants healthy and happy is to fertilize them on a regular schedule. This allows your plants to have access to the nutrients they need without overdoing it.

Unlike the clear signs that your plant needs additional water or light, it can be more difficult to notice the signals asking for more nutrients. Following a set schedule will take the guesswork out of the equation and give your plants what they need to thrive.

When And How to Fertilize Your Houseplants

What is Fertilizer & Why is it Needed

Fertilizers contain the essential nutrients required by your plants for growth. The three main nutrients needed are (N) Nitrogen, (P) Phosphorous, and (K) Potassium. On the front of every fertilizer package, you will see a number ratio representing these macronutrients.

This is called the N-P-K ratio and represents the percentage of each nutrient in the fertilizer. A common ratio for houseplant fertilizers would look like 15-30-15.

High-quality, indoor fertilizers can also contain micronutrients. These are the other nutrients a plant needs, they are just less important than the N-P-K.

“Up, down, all-around” is a simple phrase that is an easy way to remember the primary nutrients your plants require to achieve successful growth:

• Nitrogen for vegetative growth like plant leaves or grass (Up)
• Phosphorus for root development (Down)
• Potassium for everything (All-Around)

The reason the plants need these boosts of nutrients from us is that when they are growing they use up what’s contained in the soil. When you pot a plant in fresh soil, it will start to use up the nutrients in the pot as it grows.

After about two months that soil can be depleted of nutrients, and your plant can stop growing. When we add fertilizers, we are putting back into the soil the micro and macronutrients needed for continuing growth.

When to Fertilize Your Houseplants

When your plants are in fresh soil, they don’t really need any fertilizer. Most new potting soil is going to have fertilizer and nutrients mixed into it. This is why it’s usually recommended not to add fertilizer to a newly potted plant. It’s going to be unnecessary and can even do harm to the plant.

Spring and summer are the most important times to be fertilizing your houseplants. This is when plants are growing the most and benefit greatly from the increase of nutrients that the fertilizer provides.

During the winter and colder months, your plants naturally slow down their growth as the days get shorter. This is a good time to reduce your frequency of fertilizing or stop altogether until springtime. You probably won’t harm the plants fertilizing during winter, but it can be good for the plant to give it a rest.

While each plant in your home may have slightly different nutritional needs, the truth is many common houseplants have similar enough requirements to feed them on the same schedule without doing harm.

How to Fertilize Your Houseplants

Firstly, a general rule of thumb when fertilizing houseplants is less is usually better. Even the recommended serving listed on the packaging can be a bit too strong. I like to give my plant babies less than the recommended serving amount and have had happy plants as a result.

Once spring arrives and your plants start to come out of their slumber, start fertilizing with small amounts. You don’t want to shock the plants with too much fertilizer. I’d recommend using ¼ of the serving size for the first few weeks and then work your way up into larger servings.

Using a general-purpose houseplant fertilizer will work for the majority of your houseplants. I like to use Jacks 15-30-15 Houseplant Special Fertilize for my indoor plants. Another great product that I love is Liqui-Dirt. As always, make sure you read the labels carefully. If it is your first time, you will most likely want to dilute the fertilizer a little more than it suggests to avoid “burning” your plants.

There are many different kinds of fertilizers to choose from, but generally, an all-purpose water-soluble concentrate is going to be the easiest and most error-free. We like making life as easy as possible.

With both of the recommended products above, I would use them every two weeks with my watering at the start of Spring through early-Summer. Every product is going to be a bit different in frequency, so make sure to read the application rate on the label. Remember, less is usually better.

A Special Treat: Houseplants Love Coffee

You can feed your plants coffee. No joke. As I mentioned previously in my Tips for Fertilizing Houseplants, I like to give my plants leftover drip coffee every couple of weeks as additional fertilizer. Another great excuse to make that extra-large pot of coffee in the morning. Quick Tips: Make sure your coffee has cooled and is warm temperature. Dilute it with water because drip coffee can be very acidic. You can read all about giving your houseplants diluted coffee in my post HERE.