Woman watering plants near window at home, closeup

Plants vitalize our homes and offices. They filter toxins from the air we breathe and even help boost our mood and reduce stress. Plants can even help us minimize waste in the kitchen when we apply these zero-waste plant fertilizers.

Houseplants need more than just ample sunshine and water to thrive. Providing nutrients to potted plants is essential for them to grow and have vibrant colors. Because potted plants have access to only a limited amount of soil, it is critical to provide the essential nutrients.

Although these tips are helpful any time of year, spring is an especially good time to fertilize indoor plants because the days are getting longer and plants are preparing for new growth.

Mulch With Used Coffee Grounds

If you like your morning cup of java, you probably have spent coffee grounds in your kitchen. They do make an excellent addition to your backyard compost pile if you have one, or you can apply coffee grounds and even black coffee directly to many plants. The grounds work like mulch and add organic matter to the soil.

Keep in mind that coffee is highly acidic, so some plants will like it more than others. Some houseplants that have a taste for it include philodendron, Christmas cactus, jade plants, African violets, and peace lilies.

Do: Apply a thin layer of coffee grounds over the soil in acid-loving plants or mix a bit into the soil when transplanting. Treat your plants to coffee grounds sparingly — once or twice a year is plenty.

Don’t: Avoid using coffee containing sweeteners or creamer products. Don’t overwhelm the plants with coffee because too much caffeine can stunt their growth. A little goes a relatively long way.

Hydrate With Cooled Cooking Water

When we boil or steam our food, some of the nutrients can end up in the cooking water. Repurposing this water is a low-cost way to provide your plants with some fertilizer while conserving resources.

Do: Start slowly to figure out what your plants like most. Water from cooking pasta, eggs, potatoes, or vegetables is ideal.

Don’t: Beware of burning your plants. Let the water sit and cool completely after cooking. Test it to be sure it’s cool before watering your plants.

Fortify With Aquarium Water

Freshwater fish tank water contains a lot of nitrogen, potassium, trace nutrients, and microorganisms from fish waste.

Do: Save the water when you clean out your aquarium and irrigate your indoor plants with it.

Don’t: Do not apply fish tank water from saltwater aquariums because the water can be too salty for potted plants.

Augment Soil With Human Hair

This might strike some people as odd, but hair is a great source of nitrogen for plants. Either collect hair after a haircut or remove it from a hairbrush.

Do: Cut up hair before mixing it into potting soil.

Don’t: Hair takes a long time to release nutrients, so don’t rely on it as your only fertilizer; combine it with fast-acting fertilizers.

Provide Nitrogen With Green Tea

Instead of throwing out your spent green tea leaves, save them for your houseplants. You can either apply used green tea leaves directly to the soil or water your potted plants with cooled green tea.

Do: Allow the tea to cool completely before giving it to your plants. Remove spent leaves from the teabag before applying to the soil.

Don’t: Applying hot tea to plants can hurt them so be sure to cool the tea first. Also, and avoid using tea with sweeteners or creamer. Alkaline-loving plants will not like green tea, so avoid giving it to them.

Revitalize Soils With Urine

Although this may come as a surprise, human urine makes a great fertilizer for houseplants because it contains lots of nitrogen and some phosphorus and potassium.

Do: Use the freshest urine possible and dilute it with 20 parts water.

Don’t: Don’t apply undiluted urine and apply diluted urine only occasionally because it is quite potent and contains a lot of nutrients.

Enrich Potted Soil With Ground Eggshells

Plants need calcium to extend plant walls so they can grow. Because eggshells are loaded with calcium, your houseplants will love this treat. If you have extra eggshells, you can also apply them to your garden to provide calcium or ward off slugs.

Do: Rinse the eggshells and allow them to air dry. Grind them into a fine powder by using a coffee grinder, blender, or mortar and pestle.

Don’t: Don’t apply the eggshells in large pieces because the calcium will not be available to the plants. Beware of giving your plants too much calcium. If you are fertilizing with other products, check the label to see if it contains calcium.

Use Banana Peels as a Slow-release Fertilizer

Banana peels are a great source of potassium as well as nitrogen, phosphorus, and magnesium.

Do: Cut banana peels into small pieces and mix them into the top layers of soil. Alternately, you can blend the banana peels in water and pour the mixture on the soil.

Don’t: Avoid applying banana peels on top of the soil or leaving them uncovered because they may smell or attract fruit flies.

Feed Your Houseplants To Help Them Thrive

Spring is an excellent time to transplant your houseplants that have outgrown their containers and give them some fertilizer. As the days grow longer, this can be a season of exceptional growth for plants. Giving them enough space and the necessary nutrients to grow can help them thrive!

This article was originally published on March 23, 2021. We updated it with new information in March 2023.

By Sarah Lozanova

Sarah Lozanova is an environmental journalist and copywriter and has worked as a consultant to help large corporations become more sustainable. She is the author of Humane Home: Easy Steps for Sustainable & Green Living, and her renewable energy experience includes residential and commercial solar energy installations. She teaches green business classes to graduate students at Unity College and holds an MBA in sustainable management from the Presidio Graduate School.