Homemade fertilizers use organic materials and not synthetic materials so they tend to contain less concentrated amounts of the target nutrients. This lessens the chance that plants will be over-fertilized. It also means that it will be less likely that excess nutrients will leach into the environment. Additionally, homemade fertilizers made from bulk materials can also be cheaper in the long run.
How do plants eat?
Plants need 16 key nutrients (3 macronutrients and 13 micronutrients) to carry out essential physiological maintenance and grow. All nutrients are taken up from the soil by the root and transported through the plant.
Nutrients are moved through the plant through three mechanisms. The most important nutrient transport mechanism is transpiration. This is how a plant's leaves allow a regular inflow and outflow of gases to move between the plant and the surrounding air. The release of gases from the plant lowers water density in the leaves. This deficit which is replaced by a fresh supply of moisture from further down the plant. The root pressure is what pushes water and nutrient ions upwards. These two processes are accompanied by the source-sink phenomenon, which draws water and ions from less active parts of the plant to points of active growth.
What is in fertilizers?
All plant fertilizers contain nitrogen, phosphorus, and potassium. These are macronutrients - elements found in the largest quantities in plants.
Nitrogen (N) is critical in building chlorophyll and amino acids. A nitrogen deficient plant will send the nutrient to young shoots first and then to mature leaves. Dying mature leaves can be a sign that your plant needs nitrogen.
Phosphorus (P) is involved in energy transfers for cell metabolism. It comprises the structure of cell membranes and nucleic acids. Stunting, purple leaves, and lesions are signs of deficiency.
Potassium (K) regulates stomata (small pores on the leaves that allows for transpiration to occur), maintains turgor (the water pressure in the plant that keeps it upright), and osmotic equilibrium (the transfer of nutrients in the plant from areas of high to low density). Leaf lesions are a sign of potassium deficiency, with mature leaves dying first. Potassium is particularly crucial in fruit growth.
Although plants also require thirteen other elements in smaller quantities, these micronutrients are usually found in sufficient quantities within the soil.
What are balanced fertilizers?
Balanced fertilizers contain all three macro-nutrients listed above in equal proportion.
You can identify commercial brands of balanced fertilizer by looking for the nutrient percentage figure on their packaging. Balanced fertilizers will be listed as 5-5-5, 10-10-10, or 12-12-12. These figures are called the ‘NPK’ ratios. Each number indicates the percentage of nitrogen, phosphorus, and potassium respectively in the product.
A 5-5-5, 10-10-10, or 12-12-12 fertilizer contains nutrients in a 1:1:1 ratio to one another. The only difference between these mixtures would be that you need to use less of a 12-12-12 product than a 5-5-5 product when feeding your plants, since the former contains 7% more nutrients than the latter. The rest of the product is filler material that does not impact the plant.
Use balanced fertilizer if you are not trying to encourage specific aspects of plant growth and are instead aiming for overall health.
A balanced fertilizer will be good for all-purpose use on houseplants, particularly for foliage plants that do not require more potassium for flower development. A higher ratio of phosphorus is better if you are trying to encourage fruits and seeds after flowering.
Remember that shop-bought potted plants usually come with fertilizer added to the soil. Wait a few months for the plant to deplete this store of nutrients before adding your own fertilizer.
Mix the ingredients well. Add a ½ cup (120ml) of the fertilizer into 4 cups (950 ml) of water. Water your plants with this mixture, according to your plant’s needs. The mixture will be good for three months if you store it in a cool dark place. Do not use it if it has spoiled or developed mold.
Below are links to some of our favorite sources of homemade fertilizer: (as an Amazon associate we earn from qualifying purchases)