How to Make Fertilizer Using Common Household Ingredients—and Why You Should (2024)

The most rewarding part of having a garden is watching your plants grow—and one of the key ways to make this happen is by feeding them fertilizer, a substance that is applied to the soil or plant tissues to supply important nutrients. While some gardeners opt to feed their plants man-made fertilizer, it's actually quite easy to use natural options, like everyday food and yard scraps, instead.

Why You Should Make Natural Fertilizer

Making your own fertilizer involves more work than simply picking up a bag from your local garden center—so why might someone want to create their own? For starters, it's a more sustainable approach to fertilization. "Homemade soil amendments are a great way to reduce material that would otherwise go into landfills, address climate change through carbon sequestration, and build healthy soils all at the same time," says Erik Stefferud, soils and compost manager at Longwood Gardens.

How to Make Natural Fertilizer

There are many things you can use to make fertilizer at home, but no matter what you use, you want to make sure your plants get the nutrients they need to grow. Nitrogen, phosphorus, and potassium are the key elements of any fertilizer, but ingredients rich in calcium are also beneficial to your plants.To help you understand what to prioritize, it's best to do a soil test. This will help you identify your soil's pH so you know what you'll need to amend it with. For example, if you're growing a plant that likes acidic soil, you may want to use scraps in your fertilizer that will lower your soil's pH (like citrus peels).

Eggshells

Save your eggshells and use them as a calcium-rich fertilizer. After separating them from the yolk and egg whites, place them in the sun to dry them out. This ensures that the shells aren't carrying pathogens or bad bacteria that can then be transferred to your plants. After that, crush the egg shells up and sprinkle them on top of your gardening soil.

Grass Clippings

Because grass clippings are plant material, they already contain many of the nutrients that are beneficial to the plants in your garden, including nitrogen, phosphorus, some potassium, and micronutrients. "You can put grass clipping in your garden and then till them into the soil where they'll be broken down very quickly, releasing nutrients for your gardening crops," says Dan Kemper, expert trainer at the Rodale Institute. Alternatively, you can sprinkle grass clipping on top of your soil, where they will act as a mulch layer to lock in moisture and prevent weeds.

Coffee Grounds

Coffee grounds do more than just make your morning cup of joe. They can also be used as a natural fertilizer. "Coffee grounds have a fair bit of nitrogen in them," says Kemper. To apply them to your soil, start by drying them out in the sun to remove any potentially harmful bacteria. Then, till or gently scratch the grounds into your soil where they’ll break down quickly and release beneficial nitrogen.

Tree Leaves

Tree leaves are similar to grass clippings when used as a homemade fertilizer. After raking them up, lay them right over your soil like you would with mulch. "Leaves are going to be great for adding organic matter into your soil," says Kemper. "The fungi is what is going to be eating the leaves and turning it into nutrients."

Banana Peels

Food scraps, like banana peels and citrus rinds, act as a food source for the good bacteria in your soil. Start by drying them out or boiling them in water to ensure any harmful pathogens are removed. Next, crush the peels and add them to the soil surrounding your plants.

Compost

Rather than taking individual scraps and administering them to your plants, you can turn those individual components into compost. "A compost pile would be the natural fertilizer I would strongly recommend," says Kemper. To make compost, take all your scraps (like eggshells, fruit peels, and coffee grounds) and put them into a pile with leaves, sticks, and other organic debris. Overtime, the microbes will break the pile down and turn it into fine fertilizer, which you can mix into your soil. "The stuff you buy in the store is similar, but you'll obviously be paying quite a bit more than using your own scraps in your backyard," says Kemper.

When to Use Natural Fertilizer

Whether it's man-made or completely natural, fertilizer is typically applied in the spring. "For outdoor [use], apply once in the spring to give your plants that seasonal boost to get started," says Stefferud. "In outdoor settings where soil quality has previously been poor, a second application in the fall can help increase the rate at which you improve your soils over time." As a general rule, you should never apply food waste to a garden that's actively growing to minimize the risk of pathogen crossover.