For many plant enthusiasts, fertilizers and plant foods can be overwhelming. This is likely due to the inconsistent marketing and verbiage used by companies to promote their products.
In this article we aim to explain what fertilizers are, how to use them, and answer the commonly asked question, is plant food the same as fertilizer?
While many companies sell their fertilizers under the name plant food, most additives you are adding to your soil are actually fertilizers. Plant food is a compound that is created by plants from nutrients in the soil, air, water, and sunlight.
To understand how plants eat, we need to look at the process of photosynthesis. To perform photosynthesis, plants pull carbon dioxide from the air where it is picked up by chlorophyll.
Chlorophyll is what absorbs sunlight and energy and the combination of carbon dioxide and chlorophyll creates chloroplasts.
Chloroplasts then create sugars which are transported throughout the plant with the help of water. As the water rises, it also pulls essential nutrients from the soil. These nutrients are needed to keep the plant healthy and to continue to perform photosynthesis. There are 13 necessary nutrients that plants need to function properly and stay healthy.
Plants pull these nutrients from the soil, or if the soil is depleted, they get it from fertilizers.
Fertilizers are a necessary part of keeping plants. Unless you want to change your soil annually, you will need fertilizers to keep your plants healthy, growing, and producing flowers, vegetables, or new growth.
The three main nutrients in fertilizers are nitrogen, phosphorus, and potassium. They are considered macronutrients and they are usually displayed in a 10-10-10 ratio on the side of the box or bottle the fertilizer comes in.
The numbers in the ratio can also be viewed as N-P-K or nitrogen-phosphorus-potassium. There are tons of fertilizers on the market and many have varying nutrient ratios, so you can customize your fertilizer to what your plants most need.
Generally speaking, phosphorus is good for root growth and flowering, potassium is good for disease resistance and photosynthesis, and nitrogen encourages the growth of foliage. Every plant needs all three, but some need more of certain nutrients than others.
In addition to the 3 macronutrients, your plants also need all 10 of the micronutrients. They are copper, calcium, sulfur, magnesium, manganese, iron, zinc, chlorine, boron, and molybdenum. When purchasing fertilizer, the ratio on the bottle, for example, 10-10-10 states that 30% of the bottle is macronutrients.
The remaining 70% is made up of all the micronutrients and fillers. While fillers can be negative in other facets of our lives, they are actually good in fertilizer and can aid in proper absorption and distribution.
My favorite fertilizer is a 20-20-20 that I dilute to half strength. I mainly use this on my indoor houseplants, but it would also work if you had an outdoor vegetable or flower garden.
Testing Your Soil
The only accurate way to know exactly what your soil needs is to have your soil tested. A soil test can let you know the pH of your soil in addition to what macro and micronutrients are present and in what densities. This can be a great investment into your garden and allow you to better cater to your plant’s needs.
If soil testing isn’t in your budget right now though, don’t worry. Using a general balanced fertilizer can usually get the job done well enough for your plants to be happy and healthy.
When to Fertilize
The best time to fertilize really depends on your plants and your grow zone. For houseplants, the best time to fertilize is at the start of spring and then throughout the summer, tapering off in the fall and stopping completely in the winter when your plants are dormant.
For outdoor plants like vegetables and flowers, it varies. Many gardeners will add fertilizers to their soil before planting and then will continue to fertilize during the growing season.
Choosing a Fertilizer
There are 3 main options for fertilizer. Organic homemade fertilizer, liquid fertilizer, and slow-release granules. All three have their own benefits, so let’s dig in deeper.
For many gardeners, time is of the essence and easier is better. If this describes you, slow-release granules could be your best bet. To apply the granules, you simply measure the recommended amount out of the bottle and sprinkle them on the dirt around your plant outside or in its pot.
Every time you water, nutrients from the granules will be carried down into the soil to the roots of your plants for them to absorb. These granules typically last 6-8 months, so for most plants yearly application is fine.
Controlling the dosage and customizing your fertilization schedule is done easily with liquid fertilizer. Since you have an exact formula for how many nutrients are in each ounce of product, liquid fertilizer allows you to dilute your mixture to the exact amount your plants need.
This is great for picky plants that need lots of nutrients or ones that are very picky about how much fertilizer touches their roots. You do need to fertilize regularly with this option. I usually fertilize my houseplants every other week during the growing season, so this method definitely takes more time and dedication than the slow-release granules.
If you are the DIY king or queen, you may decide you want to compost your own fertilizer. While you won’t know the exact ratios of nutrients in compost, what you produce will be completely organic and safe for your plants and keep the things you pick from your garden safe for you.
Many people choose to compost kitchen scraps, paper, leaf cuttings, grass cuttings, and old blooms. You can keep your compost either in a bin or in a pile in your yard.
Be sure to keep your compost damp to aid in the breakdown and give it the occasional stir to make sure everything breaks down evenly.
Typically, soil from a compost pile can be ready in 2-3 months and at that time it can be added to your soil. To do this, simply mix a bit of the composted soil into the old soil and get it several inches down into the pot or the ground. Do this every few months to keep your plants happy.
Avoid damaging roots when mixing in the new soil as damaged roots can easily succumb to root rot.
How Much Fertilizer to Use
Like all things in life, too much of a good thing can definitely be bad. Over-fertilizing your plants can lead to your roots being burned and can inhibit photosynthesis. It can also cause your plant’s foliage to grow faster than its roots, which will leave you with a plant that isn’t capable of supporting itself.
If you believe you have over-fertilized, you can usually mitigate some of the damage by flushing the soil with water. Giving your plant a good soak can cause the fertilizer to wash out of the bottom of your pot and give your plants a chance to recover.
Signs of over-fertilization mimic the signs of over and under watering with yellow leaves. So, before you go crazy trying to figure out what you are doing wrong, the best place to start is to check your soil. If it is already saturated, you may need to check your roots for rot before doing anything else.
It’s always better to under-fertilize than over-fertilize as your plants will let you know when they aren’t getting enough nutrients with smaller leaves and lackluster shine. My secret to success in my garden is consistency.
I water consistently and I use a small amount of fertilizer consistently. This allows my plants to become accustomed to the schedule and grow appropriately. While plants aren’t as sentient as humans, they are definitely aware of how to best grow in their environment to utilize their resources and consistent care leads to consistent growth.
Whether you are a plant newbie or an experienced gardener, knowing the difference between plant food and fertilizer can be game-changing. Even more important is knowing how and when to use them to optimize your garden and your plant’s growth.
If you find yourself overwhelmed with all the fertilizers on the market and forget how and when to use them, just remember consistency is key. Most plants are fairly forgiving, so as long as you pay attention to what they are trying to tell you, your garden should be flourishing in no time.