15 Unexpected Ingredients In Your Kitchen That'll Also Fertilize Your Garden

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Farm-to-table is a great strategy for a fantastic meal, but table-to-farm can be equally beneficial for your garden. Some kitchen staples will help your harvest grow stronger and heartier, even those that you'd otherwise toss in the trash. When searching for the best fertilizer to use in your garden, some of these hacks may surprise you with unexpected ingredients.

We talked to Edwin Dysinger, expert gardener, and co-founder of the gardening planning app Seedtime, about how to use items from the fridge, pantry, and table to help in the garden. From deterring pests to adding nutrients to the soil, these additions allow even the most reluctant gardener to enjoy a bountiful harvest. 

Many can be put directly on the soil, but don't overlook your compost pile as well when creating a rich fertilizer. In some cases, you can create a spray by diluting your fertilizing ingredient with water and taking it right to the plants themselves. From coffee grounds to salt (yes, salt), these are unexpected ways that you can boost the nutrients in your garden.

If you're a gardener, chances are you've already been let on to the secret that is coffee. Putting them in fertilizer is just one way to use old coffee grounds in the garden to keep your plants happy.

These leftovers add nitrogen and is a good way to recycle your used grounds. You can put used grounds directly onto the soil or add some to your compost. Both applications help with the balance of nutrients, which can help with plant growth. "Coffee grounds are especially useful as a compost booster," says Edwin Dysinger. "They encourage microbial and earthworm activity and contain nutrients beneficial to your garden." 

The beans and ground coffee can be acidic, potentially lowering the pH of your soil, so stick with the used stuff. You should also keep a light hand when it comes to the grounds, since too much of a good thing can cause problems for your soil. Mix leaves or grass clippings in with your grounds to make sure that it doesn't get too dense and to encourage composting even more.

If your plants are showing signs of calcium deficiency, including misshapen young leaves and dark veins within the leaves, adding eggshells to your garden may be just the thing to remedy this common problem. You can also test your soil before planting, sprinkling crushed eggshells to boost this nutrient. Acidic soil is particularly prone to low levels of calcium. But good soil is essential for a vegetable garden, especially for beginners, so don't skip the testing step when you start.

"Eggshells are high in calcium which is a necessary nutrient that will help strengthen plant cell walls and can help to prevent blossom end rot in tomatoes," says Edwin Dysinger. A lack of calcium can also pose a threat to pepper plants. In both tomatoes and peppers, the first signs are often causes the fruit tips to turn brown as they develop.

"Eggshells can be dried and crushed or pulverized and then sprinkled around tomatoes or other plants," he adds. They can also be used in your compost pile to add calcium before adding the compost to your garden. This is a good way to boost the overall nutrient content of the soil in your garden.

Banana peels are rich in potassium, magnesium, and calcium. These three nutrients are needed for plant growth. But putting the peels directly on the soil isn't necessarily the most efficient way for everything to get to your plants. Adding banana peels to your compost helps them break down and add things to your booster, which will then go on to your soil and plants.

"Most of your food scraps will be what we call 'greens' in compost terminology," says Edwin Dysinger. Banana peels are part of the "greens" in compost that are necessary for decomposition. The peels have the added benefit of pumping the compost full of nutrients as well.

If you're not composting but still want to give banana peels a try, soak them in water for a few days in a spray bottle. Apply the banana water to the base of your plants. Compared to using peels directly on the soil, this method doesn't attract nearly as many pests.

You can put many types of fish in the garden to boost the nitrogen, phosphorus, and potassium content. Anchovies are just one example, but the smaller size also helps gardeners use just what they need to add these nutrients to the soil. Like other food items, anchovies are best added to your compost to help things break down.

Anchovies are commonly used in fish-based fertilizers, which are rich in protein and nutrients that will help the garden grow. If you already use fertilizers or composts with fish ingredients, you may want to skip adding even more anchovies to your plants.

If you are using anchovies as an additive, go with the dried variety rather than tinned. Use fish that aren't packed with a ton of oil or other ingredients in tins. Oil can attract other pests that you don't want in the garden, while additives can negatively impact the soil quality. The dried version, on the other hand, can be applied directly to the compost pile or ground up to sprinkle over garden soil.

You can actually use leftovers from your previous crop to help new plants grow strong as well and potatoes are a great example. These potato tubers can sprout "eyes" if stored for long periods of time, which aren't the best thing to eat. They won't cause intestinal upset in most cases, but these sprouts aren't the most appealing part. You can cut them away, but don't pitch them in the trash if you're a wannabe potato farmer.

The sprouts make perfect starters for a new crop. Add just the sprouted portion or the entire potato. These work not just for a plentiful harvest but also as a companion for other plants. Potatoes take a lot of nutrients from the soil, so they aren't good to grow alongside other needy veggies and fruits. Onions and garlic do well with potatoes, however. Corn and beans are also good neighbors with potatoes because they all thrive at different levels. The potatoes can help keep the soil thriving underground.

You can collect leftover fruit and vegetables to use as the perfect garden fertilizer. "Food scraps can be recycled in a compost pile," says Edwin Dysinger. "Almost anything can go into a compost pile with the exception of meat, dairy and oily foods which may attract the attention of unwanted creatures." Collecting compost is easy using a countertop bin like the Utopia Kitchen Compost Bin that blocks out any odors. If you want to keep your food scraps compact before adding them to a larger compost bin, the Mill Food Recycler may be the best first step.

These are best used to build a nutrient-rich compost. Make sure to remove any seeds, since you may end up with unintentional germination and seedlings if they thrive in the compost pile. In addition to these "greens," which refers to any fresh organic scraps regardless of the actual color, you'll need some "browns" as well. These can be dried leaves, pine needles, even shredded paper. Dysinger recommends getting a good variety of greens and browns for the best compost. It should also be moist, so you may need to add a little bit of extra water or cover the compost heap to help it decompose.

Seaweed is a briny, nutrient-rich snack so it makes sense that it would be just as beneficial for plants in your garden as well. You can use just about any sea vegetable, but for something easy, stick with the dried variety that you can get on store shelves. 

Iodine is a required nutrient that many soils lack, so seaweed works great. This sea vegetable also has a lot of nitrogen, phosphorus, and potassium, three nutrients that are common in fertilizers. You can pulverize the sheets of dried seaweed, then sprinkle them over the compost pile. If you have a lot of "greens," which are fresh organic matter, you'll need even more "browns," which are dried and high in carbon. It works as a "brown" additive, which Edwin Dysinger says are necessary for the right ratio. "To have a compost pile that does not stink and attract flies, you will need to balance your 'green' inputs with 'browns' in a ratio of about 1 green to 3-5 browns," he says.

Dried seaweed also acts as a natural deterrent for garden pests while also adding nutrients to the soil. If you use a fresh seaweed, you may run the risk of attracting critters and insects. Dried seaweed, on the other hand, is easy to incorporate into your compost or directly on the soil.

You can repurpose tea bags for the garden by incorporating them into your soil or compost. If the tea bag is made with paper, it will decompose along with the rest of your compost. But if there is any metal or plastic, be sure to remove those portions before using it in the garden. You can always go with loose leaf tea in the kitchen, which can be directly applied in the garden when you're done.

Nitrogen, which is essential for healthy plant growth, is in high supply in that morning cup of tea. Potassium and phosphorus also help plants thrive and are in high supply in many types of tea. Tea leaves can help make the soil more acidic, which some plants need. It's best to test your soil to see exactly what nutrients it needs and how tea can work in there.

Most gardens experience pests at some point, however, regardless of the soil quality. Tea naturally has a strong odor and bitterness thanks to tannins. This keeps smaller animals away from your crop. The tannins also inhibit fungal growth and can kill off harmful bacteria. Before you throw that tea bag in the trash, give it another life in the garden bed.

If you're struggling with weeds, some studies and experts recommend corn flour or cornmeal to tackle this common problem. It's best to use a fine blend for easy application, but you can also use a coarser ground to get the same nutrients. Alanyl-alanine is the active part of cornmeal that helps deal with weed roots at the cellular level.

"A detailed study from India found that applying 40 grams of corn flour per pot (equivalent to about 1 ton/hectare) greatly reduced germination of multiple weed and crop seeds — many fell to ~5–10% germination — and root and shoot growth were also stunted," said Edwin Dysinger.

Rather than incorporate this ingredient into your compost, cornmeal or corn flour should be put around mature plants instead. If you use it with your intended seedlings, it could interfere with their growth as well. It will help keep weeds from germinating and let your crop grow strong.

Keep the flaky peel part of your onions to add to your garden if your soil needs potassium and calcium. You can also use the scraps in your compost pile, where they help other scraps decompose to create rich compost that can be added to the garden bed later. When dried, onion peels make an effective brown that helps other scraps break down in the pile while also adding nutrients. "'Browns' are high in carbon and are usually dry," says Edwin Dysinger. 

If you're already cooking with onions, use a sharp knife to peel onions faster. Make a small cut at the edge, but don't go all the way through the onion. This creates a type of pull tab that you can use to get the peel off in one go. You may end up with some of the interior onion as well. In that case, let it dry or separate the two sections before adding them to your compost.

You can get extra use out of bread that has gone stale by adding it to your garden. It has a lot of nitrogen, which many plants like. Beneficial critters like earthworms help break down extra bread and rolls from your dinner table.

It is also a good addition to your compost bin. Because bread is rich in nitrogen, it's considered a "green" when it comes to compost, even when it is stale and dry. "'Green means they are fresh (not dried out), moist, and high in nitrogen," says Edwin Dysinger. This contrasts with "browns," which add carbon to the mix. But you need both for the ideal balance for compost that is rich and beneficial in the garden.

Tear larger slices and loaves into small pieces to help the decomposition process occur even faster. Just be sure to keep any pieces with mold out of the garden and compost. Stick with bread that is starting to get dry, but is not at the mold stage. You can also use cereal, but watch out for extra additives like sugar, flavorings, and dyes. 

Dairy can cause problems in the compost and garden, but some amounts of milk applied to your plants can help prevent common plant ailments like powdery mildew, blight, and black spot. It's particularly effective keeping fungus in check on your plants. You can use any type of regular milk, including whole, 2%, and skim. However, flavored milks and plant-based milks won't have the same effect in the garden.

"Milk contains a compound called lactoferrin, a natural anti-fungal protein," says Edwin Dysinger. "It also seems that sunlight may react with milk proteins to create germicidal compounds."

Dysinger recommends diluting milk with water at a 1-to-2 or 1-to-4 ratio in a spray bottle. Apply the spray once per week to veggies like squash, cucumbers, melons, or tomatoes. Spray directly onto the green foliage rather than on the soil or at the root base. If you use the spray too often, it can cause mold growth, which is why Dysinger says to limit your application to weekly.

Another good source of nitrogen to use in the garden is protein-rich flour. You can find regular flour enriched with protein or go with a plant-based alternative that you have in your pantry, such as soybean or peanut flour. A little bit goes a long way to enhance the soil for optimal plant growth.

Edwin Dysinger says that using flour is as easy as sprinkling it over the top of the soil. He recommends scratching it in to incorporate it well. If you're planting new seeds or seedlings, it also make a good additive when put directly into the hole before you transplant a small plant or bury a seed.

"We have used broken soybeans as a long lasting nitrogen source for crops and peanut flour as a faster acting nitrogen source," he says. The soybeans take longer to break down, so you'll get a longer release of nitrogen in the soil. If you go with flour, you may need to reapply sooner. You can always test the soil's nutrient levels to get a good idea of how your fertilizer is working and when you need to add another boost.

Bacteria and other beneficial microbes in the garden need sugar to thrive, making molasses a good addition to your garden. Molasses also has a lot of nutrients that translate right to the soil and plants, including potassium, calcium, iron, and magnesium. In some applications, it can prevent plant diseases and deter pests. Molasses seems to do it all in the garden, from helping plants grow to keeping them healthy. You can put molasses directly onto the soil, pour a little bit in your compost, or mix it with water to create a spray. 

"When used as a foliar spray, it not only feeds microbes on the leaf surface, but it seems to deter pests such as aphids, whiteflies and leafhoppers," says Edwin Dysinger. "In this context, it can be mixed with other natural pest and disease deterrent sprays such as neem, garlic and milk. In spray mixtures, use 1 tablespoon of molasses with 1 gallon of water or other spray mix."

Salt may be an unexpected ingredient that works wonders in the garden, but rich sea salt can be a great additive with key nutrient. Sea salt has a lot of micronutrients that helps plants grow and can also be used to prevent fungus growth. 

Rather than sprinkle sea salt in the garden, you should dissolve it in water. Edwin Dysinger recommends applying it using a sprayer directly to the foliage of your plants, dissolving the salt in a small amount of hot water first. He uses 1 teaspoon of sea salt for every gallon of water that he plans to put in a garden sprayer. He also adds extra water-soluble fertilizers and fungicides to create a super spray, which he applies directly to the plants. You can use different varieties of sea salt, just be sure to check the ingredients label. Look for one that is all-natural and free of extra seasonings or spices.

"The best time to foliar spray like this is before 8 a.m. or after 6 p.m. when temperatures are less than 80 degrees Fahrenheit," he says. "Plants have little mouths or pores called stomata scattered over the leaves. The stomata close during the day when temperatures are high to conserve water."