The most common and important method for getting our crops the nutrition they need is by supplying nutrition to the root system. Foliar feeding is a practice that provides nutrients to a plant straight through the leaf and stem tissues. If you are looking for controversies within the gardening world, you don’t need to look any further than this subject.

The concept of feeding the soil and not the plant is a popular one in organic gardening, and is based on solid reasoning. In this case the concept of soil extends to nearly all grow media. Creating a living soil for your crop to grow in is a vital goal as plants need more than just macro- and micronutrients. They need the beneficial bacteria and fungi along with key hormones that are responsible for so much of a plant’s health and vigor. So why feed the leaves? Does this practice put the goal of building a healthy soil at risk?

The priority of a nutrition regimen for your crop is always to care for the root system—the rhizosphere—and see to it that the plant is thriving and vigorous through the application of the proper nutrients and microbes at the correct quantities. Some questions that comes up are: “Does foliar feeding become a part of this?”, “Does it really work and if so, what nutrients, how and when?” and also, “Am I going to damage or contaminate my crop through foliar feeding?”

It may seem as though the goal of organic soil feeding might be by-passed by practicing foliar fertilization. This may be why foliar feeding is often looked at as a poor alternative for providing plant nutrition. The key word here is ‘alternative’ and this is part of what this article will explore. Foliar feeding is not meant to be a substitute for a good soil fertility program, but as an adjunct to one, allowing the grower to quickly respond to particular plant and crop issues directly and avoid further plant symptoms. If a grower is interested in looking further into foliar feeding there are a number of points to research.

What Does Foliar Feeding Mean?

Nutrition (fertilizers) applied directly to the leaf or stem tissues rather than the root system is considered foliar feeding. These tissues can be effective at absorbing various nutrients and have the benefit of providing this nutrition throughout the plant’s cell structure rapidly. Whereas root-absorbed nutrition can often take several days or weeks to become omnipresent within the plant, foliar feeding can begin to correct a deficiency symptom much faster.

Often a plant’s rhizosphere is in poor condition and when nutrients are applied they are converted or absorbed even more slowly. The plant remains malnourished until the roots and rhizosphere are repaired or improved. The most common and compelling reason for initiating certain foliar-feeding regimens is to correct a deficiency. New growth is also receptive to foliar feeding.

Foliar fertilizers can be organic or synthetic, though often a type of synthetic fertilizer is used. It is appropriate that the type of nutrient being applied is in a form to be readily absorbed and used by the plant, so synthetics can work well. Many organic and natural fertilizers fit into this category but some are not meant for foliar feeding, they are meant for building the soil and in turn feeding the plant.

Fish emulsion fertilizers are a popular type of organic nutrient used for foliar feeding. Using seaweed extract or amino acids are other popular and successful products used for organic foliar feeding. Of course, solubility and purity will be a clear priority when selecting a product for this purpose. There is considerable information available on types of organic fertilizers that can be used for foliar feeding.

A quality synthetic fertilizer does not harm a plant when used correctly. It adds nutrients that are immediately available for plant uptake and does not contain toxins. Synthetic fertilizers do not, however, feed the soil and so by themselves cannot make the most complete nutrient regimen and provide optimal growth and maximum yield.

How Does Foliar Feeding Work?

Though many researchers report that nutrition can be absorbed directly by the stomata in the leaves, many experts claim this is not what happens as once entering through the stomata the channels are lined with a waxy substance that prevents absorption.

These reports say that there are trillions of tiny transcuticular pores on the leaf surface that are readily permeable to solutions with correspondingly small molecule size. The miniscule size of these pores limits what type of nutrients that can actually be absorbed. These debates can be further researched using the QR code at the end of the article.

If, however, some of the nutrient solution that is taken into the stomata can actually be absorbed and utilized, in addition to the access through the transcuticular pores, this, too, should be considered. The debate over this aspect of foliar feeding does not appear to be over.

Stomata are usually located on the underside of leaves and act primarily to allow transfer of oxygen and water out of the plant (transpiration) and carbon dioxide into the plant. They are small openings but they are larger than transcuticular pores, so they allow larger molecules to enter, including liquids and various chelated minerals. It is a secondary function that the stomata provide a point of useful absorption for nutrients—secondary but very beneficial.

Why Try Foliar Feeding Your Plants?

When done in conjunction with good soil feeding, foliar feeding can actually increase the plant’s uptake of nutrients from the soil. It does this by causing the plant itself to pump more sugars and energy-producing exudates from its roots into the grow media (rhizosphere) surrounding them. This improves the quality of the microbial populations in the soil. This in turn promotes new, healthy root growth. As a quick-response to plants’ immediate need for various nutrients, especially micronutrients, foliar feeding is able to deliver a rapid response.

Plant leaves are actually very efficient at absorbing nutrients. Nutrient absorption can be as much as eight to 20 times greater with foliar feeding than with root feeding. Boosting various nutrients at specific stages of development maximizes growth and vigor. Beneficial possibilities range from larger roots, more foliage, more buds and more blooms to better taste and health.

As an easy and inexpensive way to increase plant and fruit size, as well as correct deficiencies, foliar feeding can increase yield. It can also be used to encourage a plant or crop towards entering the next stage of development earlier. Theories and debates over benefits abound on foliar feeding and reduced pest infestation, but the overall concept of healthier plants fight off disease and insects better is generally agreed upon.

Is Foliar Feeding Right the Best Solution For You?

When the soil or grow media is at less than optimal condition the plant may exhibit signs of nutrient deficiency and this indicates a couple of things. For one, soil conditioning needs to be improved. This can include a range of actions from feeding, improving the beneficial microbes in the soil to changing the pH.

While beginning this new regimen of soil or grow media enhancement, the plant is still not getting the nutrition it needs, and foliar feeding can change this quickly. Blossom-end rot is a common sign of calcium deficiency and a foliar spray can quickly add calcium into the plant to cure this, while root application can be much slower, allowing more fruit damage before correcting the issue.

When a nutrient shortage seems visible in the foliage or fruit or your crop, a soil test can point out which nutrients are to blame and point you in the direction of correcting the problem. Tissue analysis testing is another way to find either toxic levels or deficiencies of nutrients. If the expense of such tests seems prohibitive, find out which of the several nutrients may be missing and try to apply all of them. Once again, applying a quality product at the right strength is vital.

Foliar Feeding Tips

If you are using a commercial product, read and follow the label. Check to see about any precipitates that may occur when mixing with other liquids. Use a fertilizer that is designed to be dissolved in water and read the label to determine purity and see to it that it is free from toxins. If your crop is sold and labeled as organic, synthetic fertilizers are not permitted, but naturally occurring minerals like iron, zinc or calcium can be.

Make sure to apply the product at the right strength. Too strong of a mixture of inorganic salt based fertilizers will burn the foliage. The pH of the solution should be in the range of 5.5 or slightly higher to avoid foliage damage and lower than 8.0 to improve uptake.

It is important to remember foliar fertilization is not intended to provide 100% of a plant’s nutritional needs, but as a tool to help correct deficiencies and optimize certain specific plant growth and health issues. It is worthwhile to see how it works by having some plants that receive additional foliar feeding while having others that do not.