Foliar fertilizer vs soil fertilizer


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by Erica Strauss May 16, 2014

Photo by Rachael Brugger

Those plants that work so hard to feed you—tomatoes, peppers, corn, potatoes, strawberries—well, they need to eat, too! Most edibles need lots of sunshine, plus a fairly rich and balanced diet of minerals. Macronutrients, including nitrogen, phosphorus, potassium, calcium, magnesium and sulfur, are important to most crops, as well as other micronutrients available in very small quantities.

Ideally, your edibles would be able to get their mineral diet from good-quality, compost-rich soil without any additional work or expense to you. However, only rarely are we gardeners blessed with perfect soil, and occasionally our plants need a little boost of concentrated nutrition. Sometimes your garden soil isn’t yet mature enough to support heavy-feeding crops; sometimes you grow demanding crops back-to-back, which is quite common in a home garden; and sometimes specific crops just need a little more of certain minerals. Root crops, for example, tend to perform better when given a bit more phosphorus. That’s when added fertilizers come in to play.

Choosing a Fertilizer
A fertilizer is anything that provides fertility to your crop. Fertilizers can be slow- or fast-release, synthetically or organically derived, and single-mineral or blended. Good old-fashioned compost is considered a slow-release, organic fertilizer because it contains small amounts of the minerals plants need, though I consider it more of a soil conditioner.

There are two basic ways to fertilize your crop: amending the soil and foliar feeding. We’ll look at both to show you how they work and help you decide the best method for your farm.

Fertilizer Method 1: Amend the Soil
To amend your garden soil, dig an appropriate amount of dry fertilizer into the garden bed before a crop is seeded or transplanted. As the plant grows, the roots of the plant have access to the fertilizer mixed into the soil, and chemically break off the mineral components needed by the plant.

After the crop is established, you can add fertilizer to the soil by side-dressing, aka banding. Lightly sprinkle your fertilizer of choice in the soil alongside plants, then gently work it into the top inch or so of soil. Side-dressing is typically done with granular fertilizer, but it may be done with liquid drenches for faster root uptake.

Feeding the soil is the most efficient way to get great results in the garden. When compost and other soil conditioners aren’t enough, adding soil fertilizers can help ensure your plants are getting the nutrition they need.

Making Amendments Work
Unfortunately, there is no one-size-fits-all fertilizer. Plants tend to grow to the level of least fertility. If one mineral is deficient, strong, vigorous plant growth isn’t possible. However, some minerals compete with each other or build up in the soil, so thoughtlessly adding fertilizers can do more harm than good. Adding an amendment your plants don’t need wastes money and can lead to compounded nutrient problems, excess salt in the soil and groundwater pollution. Therefore, your goal when using soil-amendment fertilizers is to balance fertility levels for optimum plant growth by supplementing minerals that are lacking.

If you aren’t sure what your soil needs, have a soil sample tested by a university extension or lab. Skip the at-home DIY test with the little colored pills—you’ll make up the moderate cost of a highly accurate soil lab test with better-targeted fertilizer purchases. The soil test will also tell you if your soil has a pH problem that needs correcting—a common reason plants are unable to thrive even if there’s plenty of soil nutrition available.

Is it For You?
Soil amendments work with the natural uptake processes of the root system and tend to support greater nutrient mobility throughout the plant. One of the biggest benefits, especially to farmers strapped for time, is that you can add a variety and quantity of fertility amendments at once. Plus, soil amendments are the only way to deliver long-lasting fertilizer to the root zone, and they’re typically less expensive than foliar applications.

However, there are things you need to watch out for when using soil amendments. Synthetic chemical fertilizers can easily be over-used in a landscape or garden. Even if direct harm to the crop is avoided, excess nutrients wash into the groundwater and cause pollution. Soil fertilizers, particularly organic fertilizers, are slower-acting than foliar feeds, so you’ll need some patience and planning. You also will need to have cash: Slow-release, coated synthetic fertilizers tend to be expensive.

Go-to Amendments
I garden organically, and generally stick to the slower-release, organically derived fertilizers. In addition to regularly supplying my soil with compost and lime, I supplement with seed meal, used coffee grounds, gypsum, bone meal, fish meal and blood meal.

  • A balanced organic fertilizer (2-2-2 or 5-5-5) from one of the major manufacturers is good for basic background fertility. Fish meal also supplies a nice balance of nutrients, with an emphasis on nitrogen.
  • Gypsum supplies calcium.
  • Bloodmeal is a fast-acting nitrogen source.
  • Bonemeal supplies phosphorus.
  • Seed meals typically supply nitrogen, plus lower amounts of phosphorus and potassium.

Fertilizer Method 2: Foliar Feed
Foliar feeding is the fertilizer method in which you directly apply a diluted liquid fertilizer to the leaves of the plant. The plant absorbs the nutrients in the fertilizer spray directly through the leaves. If amending the soil is like making sure your plants have enough food to eat, then foliar feeding is like giving your plants a shot of liquid vitamins.

Plants primarily absorb nutrients through their roots, and the amount and types of nutrients that can be absorbed via the leaves is quite limited. However, acute nutrient deficiencies can often be identified and corrected more rapidly via foliar fertilization than slower-uptake soil amendments.

Making Foliar Feeds Work
Healthy plant leaves have a waxy coating called the cuticle. This allows water to bead up and run off the leaf, dripping down and naturally irrigating the drip line of the plant. Foliar sprays must have a wetting agent added that allows them to penetrate that waxy coating. Commercial spray fertilizers will typically include a wetting agent, but DIY types can add a few drops of biodegradable liquid dish detergent to each gallon of dilute foliar fertilizer.

True foliar feeding, with fertility delivered solely through the leaves, is quite unusual in a backyard setting. Typically, when liquid feeds are used in a garden setting, plants are sprayed heavily. The vast majority of the liquid feed drips down to the soil, where it penetrates the soil and can be taken up by the roots. In this way, it becomes more like a liquid side-dressing or soil drench feed to the roots than a true foliar feed.

Is It For You?
Foliar feeds are ideal to correct specific nutrient deficiencies very quickly. Calcium, iron, potassium and zinc deficiencies respond particularly well to foliar feeds. In combination with soil drenching, foliar feeding can provide balanced background fertility, and if you also perform a leaf analysis, it’s a safe way to investigate nutrient deficiencies in specific crops.

However, it’s important to note that foliar feeds are often not the most efficient fertilizing solution. Major nutrients cannot directly enter the leaves of the plant in enough quantity to provide for the total requirement of the plant, and some nutrients aren’t mobile enough to migrate away from the leaves throughout the rest of the plant. Foliar feeds must be reapplied frequently unless underlying soil deficiencies are corrected, and the spray solutions risk burning delicate leaf tissue unless fertilizer concentrations are carefully measured. Not all nutrients and nutrient blends are well suited to foliar feed delivery, and typically products designed for foliar application are more expensive than equivalent soil-feed fertilizers.

Go-to Foliar Feeds
All foliar feeds work best when delivered in a very fine mist. A wetting agent is essential to help the feed stick to the leaves long enough to be absorbed.

  • My favorite all-purpose foliar feed and soil drench is organic fish emulsion.
  • Kelp based foliar feeds are popular because they are a rich source of micronutrients.
  • Chelated iron is frequently used as a foliar spray used when native soil pH is too high to allow adequate plant uptake of iron. However, correction of soil pH is a better long-term solution.

Whether you use one of these fertilizing methods or a combination of the two depends on your farm’s soil, the crops you’re growing and your farming strategy. With some extra care and attention to what you’re feeding the soil, you have a chance at a healthy, productive crop for the upcoming growing season.

Journal of Plant Nutrition

Foliar fertilization is a widely used practice to correct nutritional deficiencies in plants caused by improper supply of nutrients to roots. The aim of the present study was to determine the efficiency of different forms of nitrogen–phosphorus–potassium (NPK) fertilizers applied to maize (Zea mays L.), either to the soil or to the leaves. Two sweet corn plants (CV Jubilee) were grown in plastic bags with 10.5 kg silt loam desert soil (Typic Haplocalcid). Before planting, the soil was mixed with zero (control), half or full dose of 0.6 g N, 0.4 g P, and 0.3 g K per pot as mineral forms, or as the “Global-Green” (GG) foliar fertilizer. Three forms of foliar fertilization were applied once a week in equivalent concentrations of N, P, and K (0.12 g N, 0.08 g P, and 0.06 g K/L): Mineral forms (NPK), GG, and “Fertilizers & Chemicals” (F&C) foliar fertilizers; plain water acted as the control. The plants were harvested after 55 days. The roots were washed from the soil and length measured. The shoots were measured for leaf area, fresh and dry wt, and leaf contents of chlorophyll, N, P, and K. All indices increased in response to all forms of foliar fertilization (FF), but no significant difference was obtained between the different forms. Global-Green was less effective as a soil fertilizer (SF) than NPK. The effectiveness of FF appeared to be limited by the holding capacity of leaf surface area for the liquid fertilizer. It was concluded that FF may partially compensate for insufficient uptake by the roots, but requires sufficient leaf area to become effective.

Pros and cons of granular and liquid fertilizers

There are several ways to categorize fertilizers. One logical way to look at them is as “granulars” and “liquids.” For the purposes of this comparison, anhydrous ammonia (technically a liquid) will not be considered.

Dry fertilizers are generally incorporated into granules. Fertilizer blends can be created by mixing individual granular fertilizer of known analysis (e.g., 46-0-0, 18-46-0 and 0-0-60) in the proper ratio to create the desired blend. Dry fertilizers can be ground applied as a broadcast; applied at planting as a band, often placed 2 inches to the side and 2 inches below the seed (2-by-2 placement); or applied as sidedress and cultivated shallowly into the soil. When farmers have access to custom blended granular fertilizer, they can fine-tune their crop fertility program and potentially improve crop production efficiency. If all goes well, this can result in more profitable crop production.

Liquid fertilizers have greatly increased in popularity in recent years. They can be either ground applied or foliar applied. Liquids can be broadcast, used in a band application at planting and as mid-season sidedress. When foliar applied, the plant nutrients are absorbed through the leaves and are more readily available for plant use than if ground applied. However, the availability of foliar applied nutrients is short-lived and not continuous for the rest of the growing season. Foliar applications are a good way to correct mid-season deficiencies or supplement soil applied nutrients.

Although there is no difference in the total amount of nutrients supplied by either granular or liquid fertilizer for a specified plant nutrient application, there are differences:

  • Spatial: The distance from plant roots to fertilizer nutrients. Less mobile nutrients like phosphorus can’t get closer than the individual granule containing them. In liquid form, they are more mobile in the soil water solution.
  • Salt content: Granular fertilizers can be “hot.” Roots can steer away from a band of granular fertilizer that contains high levels of nitrogen and potassium. Liquids are often preferred for “starter.”
  • Consistency: The nutrient content is identical in every drop of liquid fertilizer, while granulars have individual nutrient components in each granule.
  • Equipment: The cost of converting equipment to handle liquid fertilizer can be an obstacle.

Here is a short list of advantages of both fertilizer types.


  • Ease of handling and application (once set up)
  • Ease of blending
  • Uniformity of application
  • Starter and in-season application
  • Blend with crop protection products


  • Cheaper in bulk
  • Easier to store (does not “settle out” over time or “salt out” in cold weather)
  • More efficient for heavy pre-plant applications
  • Slow-release options (polymer-coated urea)

Michigan State University Extension does not necessarily recommend one type of fertilizer over another. However, farmers should consider costs, ease and convenience of application, and potential plant response when making fertilizer decisions.

Spray-N-Grow is pH and temperature sensitive and must be mixed at a minimum dilution of one (1) ounce of Spray-N-Grow per gallon of water. These three factors will allow the product to activate. When the mixed solution has activated, you will notice a slight color change. The pH of the mixing water should be 7.1 or higher. If your water pH is low it can be adjusted using common baking soda or any soluble alkaline base. The water temperature should be 80° to 100°F.

Add the indicated amount of Spray-N-Grow to warm water (80° to 100°F) and let the solution stand for 2 minutes. Note: We recommend one (1) gallon per 100 gallons of water.

You will notice that the color of the solution has changed from that of “clear water” to a “tannish” or yellow color. This color change may be very slight with some water and you may not detect it unless you compare it to a glass of your regular untreated water (set them side by side on a white sheet of paper).

If you do not notice a color change:

1. Use baking soda to adjust the pH of the mixing water:

Protocol for adjusting water pH:
Add 1/2 teaspoon of baking soda for every gallon of water.

Amount of baking soda to add based on 1/2 teaspoon per gallon

25 gallon tank / add 2 tablespoons
50 gallon tank / add 4 tablespoons
100 gallon tank / add 8 tablespoons or 1 cup
200 gallon tank / add 17 tablespoons or 1 cup
300 gallon tank / add 25 tablespoons or 1-1/2 cups
400 gallon tank / add 34 tablespoons or 2 cups

If you still do not notice a color change after adding the recommended amount of baking soda, repeat until you notice the change in color. In some cases where water pH is very low it may be necessary to add up to two (2) teaspoons of baking soda per gallon of water to achieve your color change. Remember, this color change may be slight.

After you have run this test one time, you will know how much baking soda will be necessary for future applications of Spray-N-Grow.

For example: a 200 gallon tank might require 200 x 1 teaspoon of baking soda = 50 teaspoons = 17 tablespoons.

2. Make sure that your mixing water is between (80° to 100°F). If your water is not at least 80°F,you may not receive a color change.

We have had a few growers comment that warming a full tank to 80° – 100°F is tedious, so we conducted some research and found various methods that effectively speed up the process of warming the water. The following protocol produces excellent results with ground water temperatures of 55°F and warmer:

Protocol for warming water:
Heat 1/2 of the water required to mix the amount of Spray-N-Grow you will use. Add enough Spray-N-Grow for the entire amount of solution you are mixing. Allow this to stand for 15 minutes. Add the other 1/4 of the water (normal temperature) to the tank. Spray your crop according to protocol.
If you need to mix 400 gallons of Spray-N-Grow mixture, heat 1/4 of the water (100 gallons) to 100°F (38°C) and add four (4) gallons of Spray-N-Grow. Allow this mixture to stand for 15 minutes. At this point, you should see a color change to a “tannish” or yellow color. Add the remaining 300 gallons of water at normal temperature, mix and spray your crops according to protocol.

If your ground water temperature is less than 55°F you need to warm your 100 gallons of water to 105°F to 110°F. Do not warm the water above 110°F, and also do not use less than 1/4 of the required water volume for the warming process.

The outside temperature is not a factor and neither is tank cooling during application.

3. Confirm that you have added the minimum dilutions of Spray-N-Grow to the water.

We recommend adding one gallon of Spray-N-Grow per 100 gallons of water. (Minimum of one ounce per gallon)


The best times of day to apply Spray-N-Grow are:

  • Pre-dawn until 9:00 am (Best choice, the dew on the plants is okay)
  • Just before sunset through late evening

Stomata are open during these hours and Spray-N-Grow is used much more efficiently by the plant.

Use of Spray-N-Grow with other products:

DO NOT apply Spray-N-Grow within 5-7 days after applying either herbicides, pesticides or fungicides unless they are the type that biodegrade within a short time. Then apply Spray-N-Grow after that time period or 5-7 days. You can apply herbicides, pesticides or fungicides anytime after 5 days have passed after applying Spray-N-Grow.

Tank cleaning:

Be sure to thoroughly clean your spray tank before using it for Spray-N-Grow. We suggest using a sudsy ammonia solution or one of the commercial washes that neutralize herbicides.

If you have any questions on this please call us at 1-800-288-6505.

Spray-N-Grow Story

By Bill Muskopf, chemist and avid gardener

Thirty eight years ago, my wife Ethel and I sold Spray-N-Grow from our home. With full time jobs, we worked evenings and weekends. Our tiny company relied on high school students to pack orders in the warehouse (our garage) and a friend to help in the office (our spare bedroom).

Gardeners across the country soon learned what we already knew. Spray-N-Grow Micronutrients produced more, larger blooms, tastier fruits and vegetables, larger harvests, and stronger, healthier plants. Scientific tests confirmed gardeners’ results.

In 1985, we moved to a real office/warehouse and waved goodbye to our day jobs! A few years later, I developed Bill’s Perfect Fertilizer and wetting agent Coco-Wet as perfect complements to Spray-N-Grow Micronutrients.

Our Spray-N-Grow catalogs feature photos that show your Spray-N-Grow success stories. They are also filled with all natural, nontoxic and organic products that are safe for people, plants and pets. My daughters, Melanie and Natalie now manage our family business. Now, their kids also work with Spray-N-Grow.

I am very grateful for you − gardeners who love Spray-N-Grow. Thanks for telling your friends about our products and for sharing photos of your gardening successes.

My Choice − The Natural Way

For many years, I have been concerned about the overuse of chemical fertilizers, fungicides, insecticides, and herbicides. We complain farmers use too many of these products, but gardeners and homeowners do as well. Here are some changes I’ve made:

  • Grow your own vegetables, fruits and herbs using organic, all natural or nontoxic products.
  • Use organic, all natural or nontoxic fertilizer and weed killer for lawns.
  • When you can’t grow it yourself, buy organic. It costs a little more, but worth it. It also supports organic farmers.

Let’s all be protective of our families and good stewards of the land, today and tomorrow.

Farmers use Spray-N-Grow to increase their profit

In the 1980’s, an Amish farmer began using Spray-N-Grow Micronutrients to treat his crops. Now, thousands of commercial growers use it because of scientific research results. Spray-N-Grow Micronutrients has been tested on 95 crops, in 11 states and 8 countries.

The research shows Spray-N-Grow Micronutrients:

  • Increases blooming and fruit set
  • Increases yields
  • Prolongs storage life of fruits, vegetables and flowers
  • Produces earlier development and harvest

Farmers know these proven results produce better crops and increase their profits!

Visit to read our research and to learn how Spray-N-Grow Micronutrients can increase your profit. Please contact Natalie at 800-288-6505 or email [email protected] for a personal crop protocol.

Proper Use of Foliar Sprays

While not a substitute for healthy soil, foliar sprays are an effective way to supplement the nutritional needs of your plants. To properly use and fully benefit from your foliar sprays, keep these notes in mind:

  • Foliar feeding should be done in the early morning or late evening, and in temperatures below 75°F (24°C), since heat causes leaves’ pores (stomata) to close.

  • The underside of leaves have more stomata because less evaporation will take place in the cooler, shady underside. This means that it is important to also spray the undersides of the leaves, not just the top.
  • Clones and plants in the vegetative stage will greatly benefit from foliar feeding. Since clones have no roots, they will extremely benefit from foliar sprays as it will aid the rooting process.
  • It is recommended to avoid using foliar sprays during the flowering stage. Spraying flowers will increase their chance of developing a mold or mildew. If you need to spray during the flowering stage, it is important to keep the lights off/temperature down and to keep an eye on your flowers.
  • Plants absorb nutrients through the bottom of the leaf much quicker than they do through the roots and stem.
  • Foliar sprays are typically less concentrated than soil fertilizers.
  • Fertilizers applied via foliar sprays are more effective and faster than when it is applied to the soil. However, foliar sprays are only short-term solutions for stressed plants. It’s important to remember to also pH and test the ppm of your soil runoff to determine the health of your soil and to make the appropriate changes to your reservoir/feedings.
  • Natural compounds used in sprays such as milk, kelp, compost Teas, and fish emulsion are also very beneficial.
  • Insecticidal soap and other surfactants can be used as a wetting agent to help the foliar application spread and stick to plants.
  • The pH of your foliar sprays should be slightly acidic (~5.8) to allow the solution to easily penetrate the cuticle (due to the complex electrostatic repulsion and attraction phenomena, which is regulated by pH within the cuticle) and be absorbed by the leaves. The optimum pH will vary with each nutrient and strain of plant.
  • Atomized spray nozzles are recommended as misty sprays are more efficient and will allow for better absorption and coverage. Sprays that aren’t misty won’t be as easily absorbed by the plant.

To learn more about foliar sprays and how to combat specific issues, enroll in an Oaksterdam University Horticulture course! Check out our schedule here!

How To Foliar Feed Your Marijuana Plants

Foliar feeding can be incredibly beneficial for your marijuana plants. Although this tends to go against popular perception, marijuana plants require regular spraying and/or misting. Plants can and will absorb nutrients from their leaves with a nutrient solution mixture.

Foliar feeding provides a rapid boost to your marijuana plants, ultimately producing larger, better, and more bud-filled harvests. That being said, foliar spraying cannot replace a standard root feeding regimen. Instead, it provides a quick way to get supplementary nutrients to your plants.

Foliar feeding essentially means that you spray fertilizer straight onto the leaves. It provides nutrients via foliage rather than roots. The process has been the subject of a number of scientific and anecdotal studies, prompting many growers to use it in their growing programs. A regular regimen of spraying feeds the plant via its stomata—microscopic openings situated in the middle of two guard cells—with direct nutrients. Regular spraying also provides clean and open stomata for your plant. Alterations in water content around the guard and other secondary cells force the stomata to open and shut as a basic response to water status changes. Download my free grow guide for more tips about foliar feeding marijuana plants.

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Marijuana plants continue with the process of photosynthesis by mixing together a number of different ingredients in their leaves. Materials can be gaseous (e.g. carbon dioxide), liquid (e.g. water), and energy (light). Simply looking at the plant’s leaves gives you an insight into how they can create food. Stomata are vital for providing access to and from the plant for gaseous materials. Stomata are like tiny pores in the skin of your plant. If more carbon dioxide is necessary for photosynthesis, the stomata will open. If the leaves overheat and need to let water escape during transpiration, the stomata will open, allowing the water to leave.

Foliar feeding comes with several advantages. Fertilizers that are applied via foliar feeding are usually 3 to 5 times more effective than standard root fertilizers. Foliar feeding can also mitigate any stress that plants feel because of their nutrition. Nutrients from foliar sprays also make elements like iron more accessible to your plants when they would not otherwise be available in the soil, water, or hydroponic solution.

TIP: Grow your own marijuana? Buy your seeds in my shop.

Clearly, foliar spraying is great for correcting nutrient deficiencies because of how fast absorption occurs through the leaves. The results will be almost immediate. The ideal time for foliar spraying is the early morning if you’re growing outside and whenever the light turns on if you’re growing inside. The stomata are open when the light is on them. It should be noted, however, that a temperature of 80 degrees or more will make the spray less effective because many of the stomata will be closed.

Clones, young plants, seedlings, and every marijuana plant in vegetative state will experience extreme benefits with foliar feeding. Because clones aren’t rooted, they require foliar feeding as a means to develop roots and avoid yellow discoloration (a frequent problem for cloners).

When a marijuana plant enters flowering stage, it is advised that you stop foliar feeding. Marijuana will naturally secrete a resin for insulation when the environment is hot and dry. This keeps the plant cool. If you use foliar feeding during flowering, then it’s important to decrease the temperature of the plants to avoid mixing fertilizer with the resin. Indeed, foliar feeding is only recommended from vegetative state until about two weeks into flowering. You also don’t want your plants to have any residual nutrients on the surface when you harvest. It will result in a heavy, nutrient-infested smoke.

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Any fertilizer that is created for soil or hydroponic systems is perfect for foliar sprays (especially ones that have trace elements, or micronutrients). In most cases, you should mix the fertilizers at reduced strength to avoid fertilizer or nutrient burn. A spray with a strong mixture of nutrients couples with bright, intense light can produce light reflection from water droplets that causes your leaves to burn. Foliar feeding is ideal with mist-style sprayers. Small particles will result in a better response from your plants. You will also have to use less fertilizer to achieve the exact same result.

A Brief Overview:

  • Spray with a fine-misting spray bottle.
  • Mist or spray at least once per day in the early morning (or when you turn the lights on)
  • Mix root (nutrient) fertilizers at 50% of their described strength. Something like Grow Booster
  • Spray the entire marijuana plant.
  • Foliar feed clones, seedlings, and plants in vegetative state.
  • Stop foliar feeding two weeks into flowering.
  • Watch “em” Grow

If you want start growing your own marijuana? Download my free grow guide and order some (5 + 5 free). We ship seeds to the US, CA and many other countries. For any growing related question please visit the marijuana support page.


The founder of I Love Growing Marijuana, Robert Bergman, is a marijuana growing expert that enjoys sharing his knowledge with the world. He combines years of experience, ranging from small-scale grows to massive operations, with a passion for growing. His articles include tutorials on growing…

The Do’s and Don’ts of Foliar Feeding

Within the hydroponics industry, there are two main types of feeding regimes: organic and non-organic nutrients. Both these feeding systems pass nutrients into a plant’s vascular system via the roots. There is, however, another way into the plants vascular system. A secret way in.

This secret way is foliar feeding. A commonly overlooked method used in vegetative and flowering stages, foliar feeding allows for nutrients to pass into the vascular system through direct leaf and stem absorption.

Foliar feeding can be a powerful ally to supercharging your plants ready for bumper yields. However, there is a catch. If it is not carried out correctly, it can have such a detrimental effect on your plants that they could be dead within 24 hours.

So, let’s have a look at the dos and don’ts of foliar feeding in the vegetation and flowering stages of your plant’s life.

Foliar Feeding: The Don’ts

Don’t Use a Foliar Spray When Your Lights Are On

If you are growing in an environment with a powerful artificial light source, the last thing you would want to do is to cover your plant in a liquid while the light is on. The plant cannot absorb the freshly sprayed liquid fast enough.

The first thing that’s going to happen is that the liquid will act as a lens, amplifying the heat from the lights and burning the leaf. Second, the plant will choke. Usually, when a plant gets too hot, its stomata open to release heat, gas, and water to cool down. However, it will not be able to breathe or self-regulate if the leaf is covered in a liquid that is causing its surface to burn.

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Don’t Use a Foliar Spray if it Will be Detrimental to Your Growing Environment

Foliar feeding increases the humidity within the growing environment. While this is great while your plant is in its vegetative stage, it can be a problem when your plant is in flower. During the flowering stage, your humidity is already high. Environment is such an important factor in modern hydroponics that I personally wouldn’t do anything to mess it up.

Don’t Use an Overly Concentrated Foliar Spray

When using a foliar spray, make sure you read the instructions twice and stick to the dilution rates on the label. In fact, I’d even recommend over-diluting the foliar spray just to make sure that you don’t use a mix that could be too strong for your plant (after all, all plants are different).

Foliar Feeding: The Dos

Do Use a Foliar Spray at Lights Out

The best time to use a foliar spray is at lights out. When a plant enters a dark period, its leaves take around 15 minutes to relax. It’s during this time—right after the lights turn off and before the leaves relax—that the stem and leaves are in their most effective absorption period.

Spraying your plant at this point also means that it has the maximum amount of time to absorb the nutrients. If you were to spray your plants too close to lights on, the plant could still be wet when the lights come on. This would have the same negative effects on the plant as if the foliar spray was applied when the lights were on as discussed previously.

Do Use Proper Technique When Foliar Spraying

Cover the plant’s leaves and stem with a light spray. Remember, less is always more as your plants need to absorb all this liquid before the lights come back on. If the leaves are dripping wet, you have used too much. It may take you a few attempts to get it right.

A great tip is to use a foliar sprayer that can be adjusted to expel a fine mist. Again, the finer the mist, the better it will be for the plant to absorb. There are also spray bottles that can be used upside down, which is great for getting into tight spaces and spraying the bottom of leaves.

Do Use Foliar Absorption to Your Advantage

Foliar sprays are a great way to tackle nutrient deficiencies. For example, if your plant starts to show signs of calcium and magnesium deficiency while you are running a nutrient-rich feeding regime, you could look to use a cal-mag foliar spray at lights off every five days to rectify the issue. This way you don’t have to change your standard feeding regime.

This is especially useful if there are multiple plants in your system and only a few are showing signs of a deficiency. The deficient plants can be directly treated with a foliar spray without jeopardizing the other plants feeding schedule.

There is a great range of foliar nutrient feeds out there. Some reduce internode spacing in the vegetative stage by creating more branches, some increase the number of flowering sites while the plant is in the flower stage, and some help with the overall health of your plant by combating deficiencies, pests, and diseases. The list goes on.

So, the next time you grow, consider using the secret way in to help take your plants to the next level.

For further reading, check out The Possibilities and the Realities of Foliar Feeding, which provides a more scientific look at how plant leaves absorb foliar sprays.


Author: Mr. Guy Sela, agronomist, expert in plant nutrition and irrigation.

Foliar feeding is a common practice of supplying nutrients to plants through their foliage. It involves spraying water-dissolved fertilizers directly on the leaves.

Many believe that foliar feeding is favorable over soil application and it is associated with higher yields, and better fruit quality.

However, many open questions and uncertainty still surround this practice.


Under certain conditions, foliar feeding has an advantage over soil applications.

Limiting conditions – A foliar feeding is recommended when environmental conditions limit the uptake of nutrients by roots. Such conditions may include high or low soil pH, temperature stress, too low or too high soil moisture, root disease, presence of pests that affect nutrient uptake, nutrient imbalances in soil etc.

For example, micronutrient availability is greatly reduced in high soil pH. Under such conditions, foliar application of micronutrients might be the more efficient way to supply micronutrients to the plant.

Nutrient deficiency symptoms – One of the advantages of foliar feeding is the quick response of the plant to the nutrient application.

The efficiency of nutrient uptake is considered to be 8-9 folds higher when nutrients are applied to the leaves, when compared with nutrients applied to soil.

Therefore, when a deficiency symptom shows up, a quick, but temporary fix, would be applying the deficient nutrient through foliar application.

In specific growth stages – Plants require different amounts of nutrients in different growth stages. It is sometimes difficult to control the nutrient balance in soil. Foliar applications of essential nutrients during key stages can improve yield and quality.

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Limited dosage – Nutrients applied in foliar application cannot meet the entire nutrient requirements of the crop.

Phytotoxicity – Applying high concentrations of nutrients by foliar application might result in leaf burn, as water evaporates and salts remain on the leaves.

High cost – Due to phytotoxicity considerations, small amounts of nutrients should be applied at a higher frequency. However, frequent applications at lower concentrations are very costly and not practical.


Various factors affect the effectiveness of foliar feeding:

pH of the foliar spray solution – Nutrients must be in their soluble form in order for the plant to be able to absorb them. pH affects the solubility of nutrients and their interaction with other components in the water. Generally, acidic pH improves the penetration of nutrients through leaf surfaces.

In addition, pH affects foliar absorption of nutrients in three other ways:

  • pH affects the charge of the cuticle (a waxy layer covering the leaves) and
    therefore its selectivity to ions.
  • The ionic form of nutrients is pH dependent, and therefore pH can affect
    the penetration rate.
  • pH might affect the phytotoxicity of the sprayed compounds.

    We can conclude that pH of the spray solution must be adjusted according to the applied nutrient.

    Use of surfactants – Surfactants contribute to a more uniform coverage of the foliage. They increase the retention of the spray solution by reducing the surface tension of the droplets.

    Without surfactant With surfactant

    Time of the day – the best time to foliar feed is early morning or late evening, when the stomata are open. Foliar feeding is not recommended when temperature exceeds 80°F ( 27° C).

    Droplet size – Smaller droplets cover a larger area and increase efficiency of foliar applications. However, when droplets are too small (less than 100 microns), a drift might occur.

    Spray volume – Spray volume has a significant effect on the nutrient absorption efficiency. Spray volume must be such that it is sufficient to fully cover the plant canopy, but not too high so it does not run off the leaves.

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Liquid Fertilizer Foliar Application

Foliar application with liquid fertilizer is an effective method for quickly solving nutrient problems appearing in many plants. Foliar feeding allows plants to absorb nutrients faster, and also avoids many common problems that cause nutrient loss in the soil. Several AgroLiquid fertilizers are ideal for foliar feeding, and can be quickly applied to bolster plant growth at pivotal times.

Since it is applied directly to plant leaves and absorbed through the plant’s stoma, foliar application of liquid fertilizer moves quickly through the plants leaves, blossoms and fruit. Foliar feeding is most effective for micronutrients, though macronutrient support can also be provided through a foliar spray.

The best foliar feeding method depends on your plant type, the plant’s growth stage, and any nutrient deficiencies the soil may present. With the right foliar feeding liquid fertilizer program developed, foliar feeding can: make fruit grow larger, faster, and develop color sooner; prevent leaf chlorosis and stunted growth in row crops; and encourage leaf growth and photosynthetic development. To learn more about foliar feeding for your crop or orchard, work with an AgroLiquid agronomist.

What Is Foliar Spray: Learn About Different Types Of Foliar Spraying

Foliar spray fertilizer is a good way to supplement the nutritional needs of your plants. There are various types of foliar spraying options available to the home gardener, so finding a recipe or suitable solution to accommodate your needs should be easy. Keep reading to find more about using foliar sprays to maintain the health of your plants.

What is Foliar Spray?

Foliar spray, although not a substitute for healthy soil, can be beneficial when a plant is suffering from certain nutrient deficiencies. Foliar plant spray involves applying fertilizer directly to a plant’s leaves as opposed to putting it in the soil.

Foliar feeding is similar to humans putting an aspirin under their tongue; the aspirin is more readily absorbed into the body than it would be if it were swallowed. A plant takes nutrients through the leaf much quicker than it does through the root and stem.

Types of Foliar Spraying Mixtures

There is a wide variety of foliar feeds to choose from. Usually water-soluble powder or liquid fertilizers are used. If you purchase a fertilizer, be sure that there are directions for foliar application.

Foliar sprays are generally less concentrated than fertilizers that are placed on the soil. Many people use natural materials for foliar sprays such as kelp, compost tea, weed tea, herbal tea and fish emulsion.

Comfrey tea is packed with potash and nitrogen and is very easy to make. Fill a blender almost full with fresh comfrey leaves and add water up to 2 inches below the rim. Blend the leaves until all the comfrey is dissolved. Mix one part comfrey tea to 10 parts water for a foliar spray.

Using Foliar Sprays

Foliar feed should be applied in the early morning when the air is cool. Spray plants until you see the mixture dripping from the leaves.

To help the foliar application stick to plants, add a small amount of insecticidal soap or horticultural oil. Do not forget to spray the underside of leaves as well.

Foliar spray fertilizer is an excellent short-term solution for plants experiencing stress. However, it is always best to build up your soil with plenty of organic matter.

Why Foliar Spray?

Discover the benefits of foliar nutrition

A small investment that leads to big results. Discover the benefit of foliar spray with Haifa Bonus

Complementary nutrition

Foliar application is a must when soil fertilization is sub-optimal or ineffective.

In many farming practices most of the fertilizers for the growth season are applied as base dressing. Such practice often result a significant decrease of essential nutrients in the soil during the season. This may affect plant growth, and reduces yield. A mid-season foliar spray of fertilizers will balance and complete plant nutrition, and help to retain healthy and fruitful growth. A relatively small amount of fertilizers will lead to a dramatic improvement and will get the crops to optimal growth curves. This is a real Bonus. In some cases uptake of nutrients by the roots may be impaired due to low temperatures, water logging, nematodes, or other reasons. Here also, foliar nutrition is a true bonus, offering a beneficial complementary nutrition.

Corrective nutrition

Foliar sprays are fast acting and effective for treatin nutrient deficiencies.

Foliar uptake of nutrients is much faster than root uptake. Therefore foliar feeding is the method of choice when deficiency symptoms are noted, and prompt correction of deficiencies is required. Nutrients rapidly absorbed through the foliage, providing the plant with the missing nutrients, and strengthening it.

Growth boosting

A precise timing of foliar nutrition lead to growth and yield improvement.

Certain phases of plant development are highly important in determining the final yield. A foliar nutrition precisely given during these specific phenology stages ensures optimal growth, and best possible yield. In relatively low concentrations at these critical stages, foliar nutrition boosts physiological processes of the plant, ensures optimal development, and contributes significantly to higher yields and better quality.

Specific induction

Foliar fertilizers activate particular plant mechanisms

Foliar application of certain fertilizers are known to induce dormancy breaking in grapes and deciduous fruit trees. They are also efficient in stimulating flowering, mainly in mango.

Tips for a successful foliar feeding

General • Spray during the cooler and more humid hours of the day • Apply foliar spray when wind is low • Never spray plants under stress • Test for possible side-effects or phytotoxicity by a small trial, spraying a week prior to the intended commercial treatments • After spraying rinse thoroughly the sprayer and all its parts with fresh water Setting application rates • Consider both spray concentration and spray volume. • If you apply smaller (or larger) volume than recommended, increase (or decrease) the fertilizer concentration of the spray solution accordingly, to keep the total application rate per unit of area. • Avoid concentrated sprays, as they might scorch leaves. • Plants in areas of humid climate tend to have thinner leaf cuticle, which make them more susceptible to phytotoxcity. For this reason, spray concentrations must be considered more cautiously in these areas. Preparation of tank mix • Fill 1/4 – 1/3 of the spray tank with water. Add the entire amount of the fertilizer(s) and then fill up the tank with water. • When preparing tank mix that includes pesticides, it is advisable: – To keep the pH of the spray solution at level of 5.5 -6.5, to avoid alkaline hydrolysis of the pesticides. Note: In general, Haifa’s foliar products are slightly acidic, requiring lower rates of acid to set the pH of the spray solution. – To perform a compatibility test of the spray-mix prior to large-scale treatment.

A complete range of foliar nutrition products

Haifa offers a selection of premium products for foliar application, all containing pure plant nutrients, free of chloride, sodium, and any other detrimental materials.

Poly-Feed™ Foliar Poly-Feed™ Foliar is a range of fully water soluble NPK, high quality fertilizers for foliar application. Poly-Feed™ soluble NPK formulae is designed for crop feeding with optimal, balanced nutrition throughout the growth season. Haifa Bonus™ is a high-K foliar formula (13-2-44), based on Haifa’s Multi-K™ potassium nitrate. Phosphate enrichment balances the nutritional value of Haifa Bonus™, and improves its compatibility with various agrochemicals. Other Haifa Bonus™ formulae are available upon request. Seaweed extracts: small addition that goes a long way. A variety of Poly-Feed™ formulas are available, enriched with 0.5% or 1% seaweed extracts. The seaweed extracts contain a wide range of nutrients, growth bio-stimulants and conditioners that act together to improve both plant development and soil properties. The seaweed extracts catalyze cellular metabolism and enhance cellular production of growth hormones, two processes that promote plant development. – Better plant development – Enriched plant nutrition – Improved plant strength Additionally, the seaweed extracts help to increase the population of beneficial microbes in the soil. These microbes create a “biological barrier” between the plant and pathogens, and improve the natural tolerance of the plant.
More fertilizers for foliar application

  • Magnisal™ magnesium nitrate, 11-0-0+16MgO
  • Haifa MAP™ mono-ammonium phosphate, 12-61-0
  • Haifa MKP™ mono-potassium phosphate 0-52-34
  • Haifa ProteK™ potassium phosphate and phosphite, a systemic fertilizer higly recommended to enhance the plant’s resistance towards various diseases

How To Properly Foliar Spray

Foliar Spraying Tips:

  • Always use Purified (no minerals /chlorine) water to avoid clogging sprayer or damaging sensitive plant leaves.
  • pH solution to whatever either the label suggests or else to whatever pH you are currently feeding plants at. An example of this is 6.5 for Soil and 6.0 for Hydroponics.
  • Best effect is achieved by creating afine mist out of the spray content. Use of pressurized / compression sprayers like the Solo Directional Sprayer are advised. Alternatively you can get cheaper compression sprayers. In general try to get a plastic tip. They seem to work better than the Metal tip’d ones.
  • Make sure to spray undersides of the leaves where the plants stomata’s are located. Full Coverage is key.
  • It is best to spray when temp is below 80 deg. F if not using CO2. If using CO2 then spray at 86 deg. F. At this temp, the stomatas on the undersides of the leaves are open. It is best to spray at the end or beginning of day.
  • Absorption is best when enviornmental conditions are humid. 55-70% Humidity.
  • It is highly advisable to use a wetting agent /surfactant such as Saturator (for delivering additives into plant) or like Coco wet for pesticides that will “stick” better on leaves. These wetting agents are not just “detergent” or “dish soap” they will not damage the cuticle layer of the plant’s leaves. Wetting Agents will make the water molecules “wetter,” spreading them apart from one another; preventing “blotching” or grouping together of water spots. This blotching of water molecules in turn will create a magnifying glass effect which when intense light hits it can in turn burn your leaves. Wetting agents, like DutchMaster’s Saturator will also help deliver additives into the plant up to 300% better than just spraying alone (without the use of a wetting agent).
  • Always be aware of what you are spraying at your plants. Make sure to mix additives that can be combine safely with other additives. Also, make sure that you are not adding two of the same or like products together (both at full strength). (An ex. of this is blending two kelp products such as Alg-A-Mic, and GO BioWeed or Heavy Prime.)
  • Whenever spraying something new, we suggest spraying one strain of each type of plant you have. Wait to see if each plant takes to the foliar delivery well (1 day should suffice). See how that plant does. . . (This is for additives, enhancers, nutrients, or pesticides.) If this one palnt is healthy that continue to spray entire crop.
  • This is a general rule that will not apply to every additive) that whenever you spray the lights are off and fans are on for 2-3 hours making sure the leaves dry out. Then when you turn lights back on raise the up 1 more foot above where they have been.

How Nutrients and Additives are Absorbed and Translocated Within a Plant:

Plants can absorb additives and nutrients through either the stomata (main avenue) as well as through their waxy cuticle layer. That is why it is important to spray both sides of the leaves for better absorption. Although most additives get absorbed through the stomata they also can make it in through the rest of the leaf tissue as well. Since the stomata are the main pathway into the cell, we will focus our conversation on them. Under most conditions, stomata open when the light strikes the leaf at the beginning of their daytime (morning) and close at the end of their day during their dark period (plants night.) The immediate cause is a change in water pressure (turgor), of the guard cells within the plants leaf tissue. Each guard cell has a thick, yet elastic inner wall. When turgor develops within the two guard cells flanking each stoma, the thin outer walls bulge out and force the inner walls into a crescent shape. This opens the stoma. When the guard cells lose turgor, the elastic inner walls regain their original shape and the stoma closes.

A very permeable pathway exists for the movement of nutrients through the surface of the leaf to the various living tissues within the plant. It has been found to be very fast – roughly an hour to move from the leaf to within the plant itself. Most applied additives are absorbed into, and throughout the entire plant in a day’s time. Such applied nutrients move rapidly to points of new growing points of stems and roots, thus having an immediate effect on growth and development. Soil, or root zone applied fertilizers / additives can take much longer to get into the plants inner tissues and effect growth.

We recommend foliar spraying at least every 3 days. Please feel free to mix and match the foliar recipes below. Follow their suggested use time for each given recipe. Also ask us about some of our other favorite recipes.

Foliar Recipe with Heavy Foliar, Heavy Roots and Heavy Fire:

Heavy Foliar provides for both full spectrum plant nutrition and protection. It does this by increasing the biochemical rate of photosynthesis through correct concentrations of select dichotomous plant based carbs or what we call “Pre-Formed Photosynthates”. Heavy Foliar also provides a highly absorbable form of calcium, a slew of micro-nutrients, which when combined tprovide for environmental plant protection.

Application Instructions:

Apply this spray every 3 days. Start with just 40 mL of Heavy Foliar per quart of purified (RO) water and ramp up to the following recipe by week 2 of Veg. Maintain this level throughout weeks 1-4 of Bloom.

Quart Sprayer – Mix 30 mL of Heavy Foliar, 1 mL of Heavy Roots and1 mL of Heavy Fire in one quart of purified (RO) water.

Foliar Recipe with Great White, Axiom, and Coco Wet:

This is an all around metabolism boosting, immune system building, pathogen-warding off tonic that will keep your plants standing strong and growing faster than you have seen before. We can’t talk highly enough of this potent concoction. Your plants will be singing and soaring towards the sky.

– Apply this spray every two weeks.

Quart Sprayer – Mix 1/4 tsp of Axiom, .06 gram of Great White and a few drops of Coco Wet

Gallon Sprayer- Mix 1 tsp of Axiom, 2 tsp of Great White and Coco Wet at 1 tsp in a one gallon spray bottle filled with purified (reverse osmosis) water.

Einstein Oil and Coco Wet:

Neem oil is a great preventive for warding off / controlling a variety of pests (spider mites, thrips, whitefly’s, aphids, etc.) as well as keeping powdery mildew at bay. Neem works best if sprayed consisently every 3 days. We suggest Einstein Oil because it is “cold pressed” and retains more of the active indgredients than other products. Mix with Coco Wet and apply at lowest dosage at first. Raise dosage up slightly every spray until max application rate is reached.

– Apply this spray every 3 days. Build dosage up from lowest to highest than ride highest dosage out until 4th week of Bloom.

Quart Sprayer – Mix 1/2-2tsp. of Einstein Oil and a few drops of Coco Wet per Quart of “warmed up” purified (RO) water.

Gallon Sprayer- Mix 2-8tsp. of Einstein Oil and a 1/4tso. of Coco Wet per Gallon of “warmed up” purified (RO) water.


This stimulant / protectant (brought to us from Japan) is made from Pine Oil and is amazing at keeping plants perky and and in general “healthy”. Pine oil was proven to be a non-toxic plant defender, growth stimulator, and liquid organic fertilizer. It provides effective control against most pests and root pathogens. Pine Oil will also increase Yield significantly.

– Apply this spray every 7 days.

Quart Sprayer – Mix 1mL of HB-101 per Quart of reverse purified (reverse osmosis) water. No wetting agent is used.

Gallon Sprayer- Mix 4mL of HB-101 per Gallon of reverse purified (reverse osmosis) water. No wetting agent is used.

DutchMaster Liquid Light, and Saturator:

DutchMaster has come out with some very unique additives which greatly accelerate Plant Growth and Yield. Liquid Light is a formula of selected Amino Acids, Metabolites, and Phospholipids that works by supercharging the chloroplasts. These cells are the solar powered engines that are responsible for turning the light and CO2 into sugar. Saturator is a must! (Do NOT spray without it!) Allowing for 300% more absorption. Make sure you spray with lights ON. Raise them up to 12-24” above their normal hanging spot for the first 2-3 hours after spraying. Then bring lights back down to normal levels.

Still Have Questions?

Visit any of our many locations and our helpful staff will be able to answer any questions you have. GreenCoast Hydroponics is the leading retailer of Hydroponic Equipment & Organic Gardening supplies on the West coast. Offering unparalleled commercial grow design services and a wealth of knowledge. Amateur or pro, we can increase your yield.

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