Aquarium Water
Water your plants with the aquarium water taken right out of the tank when cleaning it. Fresh water only please, do not use water from a salt water tank. The fish waste makes a great plant fertilizer.
Bananas
Bananas are not only tasty and healthy for humans, but they also benefit many different plants. When planting roses, bury a banana (or just the peel) in the hole alongside the rose. As the rose grows, bury bananas or banana peels into the top layer of the soil. Both of these approaches will provide the much-needed potassium that plants need for proper growth.
Blackstrap Molasses
Blackstrap molasses is an excellent source of many different nutrients that plants use. This includes carbon, iron, sulfur, potash, calcium, manganese, potassium, copper, and magnesium. What makes this an excellent type of fertilizer is that it feeds beneficial bacteria, which keep the soil and plants healthy. To use blackstrap molasses as a fertilizer, mix it with another all-purpose fertilizer. A good combination to use is 1 cup each of epsom salts and alfalfa meal. Dissolve this combination in 4 gallons of water and top it off with 1 tablespoon of blackstrap molasses. Or simply mix blackstrap molasses in with compost tea. Do this only after the compost tea has steeped.
Coffee Grounds
Used coffee grounds contain about 2% nitrogen, about a third of a percent of phosphoric acid, and varying amounts of potash (generally less than 1%). Coffee grounds are particularly useful on those plants that like things a bit more acidic, such as blueberries, evergreens, azaleas, roses, camellias, avocados, and many fruit trees. I recommend that you allow the coffee grounds to dry and then scatter them lightly, as a mulch, around your plants. Avoid scattering them thickly when they are wet, because clumps of coffee grounds have a tendency to get moldy.
Cooking Water
Many different nutrients are released into the water that food is cooked in. Water that is used to boil potatoes, vegetables, eggs, and even pasta can be used as a fertilizer. Just remember to let the water cool before applying it to your soil.
Corn Gluten Meal
Corn gluten meal is a byproduct of the wet-milling process for corn. It is used not only as an organic pre-emergent herbicide, but also as a fertilizer that is 10% nitrogen. To use as a fertilizer, simply spread a thin layer of corn gluten meal and scratch it into the top inch of soil. Plant veggie starts inside the treated area for optimum nitrogen benefit, and do not worry about accidentally harming your plants. Corn gluten meal only works as an herbicide before seeds germinate, not after, so it won’t hurt plants that have already sprouted.
Egg Shells
Egg shells contain about 1% nitrogen, about a half-percent phosphoric acid, and other trace elements that make them a practical fertilizer. Calcium is an essential plant nutrient which plays a fundamental part in cell manufacture and growth. Most roots must have some calcium at the growing tips to grow effectively. Plant growth removes large quantities of calcium from the soil, and calcium must be replenished, so this is an ideal way to “recycle” your egg shells. Simply crush them, powder them in an old coffee grinder, and sprinkle them around your garden soil.
Epsom Salts
1 tablespoon of epsom salts can be combined with 1 gallon of water and put into a sprayer. Apply once a month, directly to the foliage, for a quick dose of magnesium and sulfur.
Wood Ash (From Your Fireplace or Fire Pit)
Ashes can be sprinkled onto your soil to supply potassium and calcium carbonate. Hardwood is best—and no charcoal or lighter fluid, please, as this can harm your plants. Don’t use ash in areas where you are trying to maintain acid-loving plants—the ashes are alkaline and can increase alkalinity in the soil.
Gelatin
Gelatin can be a great nitrogen source. Dissolve 1 package of gelatin in 1 cup of hot water and then add 3 cups of cold water. Pour directly on the soil around your plants once a month. This is great for houseplants!
Green Tea
A weak solution of green tea can be used to water plants every 4 weeks. Use 1 teabag to 2 gallons of water.
Hair
Hair is a good source of nitrogen, and it does double duty as a deer repellent. A good source for this hair is not only your hairbrush, but also the local barbershop or beauty salon. Many of these establishments will save hair for your garden, if you ask them for it. But do not limit yourself to only human hair. Dog hair, horse hair, and cat hair work just as well.
Horse Feed
What makes horse feed irresistible to horses is also what makes it an excellent fertilizer. The magic ingredient is molasses. To use horse feed as a fertilizer is simple and easy. It can be used as a soil amendment just by sprinkling it on top of the soil. Alternatively, it can be dissolved in water alone or combined with another organic fertilizer, and applied as a soil drench.
Matches
The old-fashioned easy-strike matches are a great source of magnesium. To use this as a fertilizer, simply place the whole match in the hole with the plant, or soak the matches in water. The magnesium will dissolve into the water and make application easier.
Powdered Milk
Powdered milk is not only good for human consumption but also for plants. This source of calcium needs to be mixed in to the soil prior to planting. Since the milk is in powder form, it is ready for use by your plants.