What Is Foliar Feeding, and Should You Use It?

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As gardeners, we all want the same things. Strong, healthy plants that produce prolific blooms in our flower beds and lots of nutritious produce from the vegetable garden. The way to achieve that goal is to provide all the nutrients the plants need. You can do this by including soil amendments, fertilizers both general and specific like your favorite rose fertilizer and maybe even foliar feeding.

What Is Foliar Feeding?

Foliar feeding is the application of high quality fertilizer through the plant’s leaves. Think of it this way — plants have “skin” much as people do. Our skin can be a way to administer medication rather than swallowing it. If you have ever seen someone use the nicotine “patch” to help them stop smoking or the patch behind the ear to prevent sea sickness when going on a cruise, both are examples of medication being administered through the skin. 

A plant’s skin is the outer surface of the plant’s leaves. A top-tier plant food spray applied to the leaves of the plant can supplement the nutrients otherwise made available through the root system. The key word in that sentence is supplement. Your plants will only be able to absorb about 15-20 percent of the nutrition required through the foliar feeding. Foliar feeding cannot be a substitute for healthy soil.

How to Apply a Foliar Feeding

It’s important that you always read and follow the directions on the bottle of the plant food spray you plan to use. Overuse of foliar feeding can “burn” your plant leaves and do more damage than good, so be sure to apply as directed. Generally, it is best to spray your plants with a fine mist of the plant food spray in the early morning when temperatures are lower. It is best to avoid applying the plant food spray in the high heat of summer as you can damage the plants. 

Apply the spray to the underside of the leaves as well as the top. Many plant leaves have a waxy coating on the top surface that will prevent the plant food from being absorbed. Some gardeners add a drop or two of surfactant like soap to help the plant food to stay on the leaves rather than just slide off the surface. 

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Remember that the plant can only absorb about 15-20 percent of the needed nutrients, so think of foliar feeding as a booster shot for your plant. If you see your plants are short of iron (the veins of developing leaves are yellow instead of green), a foliar feeding can be a quick boost for your plants. At the same time, you should correct the iron deficiency in the soil.

Maintain a Healthy Soil

Foliar feeding is important; however, successful gardening starts with maintaining good soil. The more organic matter the better when growing plants of any kind. Organic matter in your soil will help to break up clay soils and allow air, water and nutrients to be absorbed by the plant roots. If you have sandy soil, the organic matter will absorb the water and nutrients that would otherwise easily leach away. These nutrients are then available to the plant through its root system.

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Once the soil condition itself is addressed, the next step is to have your soil tested. You will need to know if the soil has adequate amounts of all the macronutrients (Nitrogen, Phosphorus and Potassium) and micronutrients like zinc, boron and iron. Most of your plant’s nutrition will be absorbed through the root system from the soil. 

When you test your soil, the results will include levels of all the necessary nutrients, along with recommendations for how to amend the soil to increase the amounts of nutrients that the test shows are too low to provide healthy productive plants. This can be done by adding specific organic materials or by the use of commercial fertilizers. 

Soil fertilizer comes in different combinations that are specific to what you are growing. For instance, there is fertilizer made for flowering plants and, even more specific, a rose fertilizer. 

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There are a number of fertilizers for the vegetable garden, but some are specifically made for plants like tomatoes.

Foliar feeding is a great way to supplement the nutrients your plants may be lacking from the soil they are planted in.