Foliar Feeding

April 25, 2005

The practice of foliar feeding has been a subject of curiosity to me for many years. Roots are made for absorbtion of water and nutrients aren't they? And aren't leaves made for photosynthesis? Can leaves really absorb water and nutrients well enough to benefit a plant?

This experiment was begun on 04/16/05 to see if a difference in growth rate could be noticed between 5 tomato seedlings which are being given foliar feeding and 5 which are not.


Comments (64)

  • jimster

    One change in procedure was made this week. Realizing that the foliage remained dry most of the time, and could only absorb foliar fed nutrients when wet, I decided to spray all the plants daily with solution A (no nutrients) This is intended to allow further opportunity for absorbtion of nutrients previously deposited on the foliage. Bear in mind that the only objective of the experiment is to determine if any evidence of absorbtion can be observed. No attempt is being made to measure the amount of absobtion.

    Comments have been made that perhaps increase in height is not the best variable to measure the effect of foliar feeding. This measure will be continued, but other variables, such as leaf color, are under consideration.


  • jkirk3279

    If you want to be sure that foliar feeding works, pick one plant and hit it with a dilute spray of Epsom Salts.

    You'll see results.

    I still like the idea of a light sensor/LED test jig.

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  • silybum

    If you would decide to use yucca extract to replace the liquid detergent, take note, yucca extract not only makes sprays stick to crop foliage, it is also a great nutritional foliar in itself. (according to Peaceful Valley Farms, where I purchase my fertilizers). They sell it as Therm X70.

    Here is a link that might be useful: Peaceful Valley Farms

  • jimster

    Well, at $100 per gallon, I guess I won't be using yucca extract. Thanks for the link though. I'm saving it for future reference.


  • jimster

    Height of Plants (inches)



  • jimster

    "If you want to be sure that foliar feeding works, pick one plant and hit it with a dilute spray of Epsom Salts.

    You'll see results."

    OK. Let's try. I added a teaspoon of Epsom Salts to Solution B (the nutrient solution). We will see any results in next week's report, at the earliest.

    So far, I have observed no noticable differences between the two sets of plants.


  • jkirk3279

    I usually use 1 tablespoon Epsom Salts per gallon of water.

    Have you come up with a green-ness test yet?

  • jimster

    I haven't come up with a green-ness test. Just using visual evaluation I thought for a while there was a difference in color. Now, however, I detect no visual difference.

    All the plants are growing well at the same rate, so far as I can tell. Their color could be better and I truly wish I could give them just a touch of root feeding.


  • jkirk3279

    I hit some of my plants with Epsom Salts spray two days ago, and one in particular turned dark green overnight.

    Now, I admit, I never ran trials like you are doing. For all I know, Magnesium Sulphate can only be absorbed by roots.

    I mention this because I forgot the whole point and watered with the solution.

    Which invalidates the test, I suppose.

    But I've always been too greedy for success to feed only half my plants.

  • jimster

    I think it is rare that foliar fed nutrients do not end up in the soil. In practice, that's fine. If it works, do it. But, because of that, all the anecdotal evidence of success with foliar feeding under normal growing conditions does not satisfy my curiosity about whether foliage actually absorbs nutrients. Most, if not all, the benefit may be from the stuff that eventually drips into the soil.

    Some, if not all, of the science which has been done re foliar feeding must have taken this into consideration. In my cursory search of the literature however, I found no discussion of it.

    "But I've always been too greedy for success to feed only half my plants."

    That is the primary reason we gardeners perform so few experiments, in the scientific sense. We want to give all our plants what we believe to be the best treatment. If our plants do well under that treatment, we are happy and attribute the success to what we have done. And why not?


  • rockymountainchile

    you could always seal off the top of the containers while foliar feeding, this would eliminate another variable in your tests... any recent updates, measurements, or photos?


  • jimster

    "...you could always seal off the top of the containers while foliar feeding..."

    That's what I am doing, Jack. Also, I keep the plants horizontal until dry, so nothing drips into the soil. I haven't yet found out if other experimenters have done that. I think they must have but, if the plants were field grown it wouldn't be easy.

    Update is coming soon.


  • atillathepun

    Suprised there hasn't been an organic/chemical foliar comparison, such as compost tea vs commercial foliar plant food.

  • jimster

    Height of Plants (inches)



  • jimster


  • jimster

    "Suprised there hasn't been an organic/chemical foliar comparison, such as compost tea vs commercial foliar plant food."

    Good idea. Want to do it?


  • jimster

    Here is a scan of a leaf from the same position on each of the ten experimental plants. Five of the plants received foliar feeding. Five did not. They are in random order. Can you determine visually which are which? Scrutinize color, size, etc.

  • gailnewgarden

    just for fun:
    No - 1, 4, 7, 9 and possibly 6?
    Yes - 2, 3, 5, 8, and 10

  • bushpoet

    yes: 2, 3, 5, 6 & 8?


  • duderubble

    2,3,5,6 & 8 are healthiest.

  • jimster

    Here is one which was posted on the Growing Tomatoes site:

    * Posted by: Steve1805 TX (My Page) on Mon, May 23, 05 at 16:07

    I'm by no means an expert but from a general observation 3, 5, 6, and 8 look the healthiest.

  • Gardenmama1

    From what I can see, 2,3,5,6,8 look the healthiest and greenest

  • BrokenAppleTree

    I'm going with 2,3,5,6,8

    ok, didn't read anyone elses until just now, looks like we all think the same ;-)

    - Brian

  • Phaethon

    I 'd say 2,3,5,6,8 and 10 look to be the most vigorous.


  • jimster

    The concensus of those who evaluated leaf samples was that leaves from plants 2, 3, 5, 6 and 8 appeared most "healthy" or most "vigorous". This corresponds with the plants which received foliar feeding. The height difference between groups N and Y also became more distinct as the experiment proceeded. It can be reasonably concluded that plants can benefit from dissolved nutrients applied to their leaves.

    This answers the question posed at the start of the experiment, "Can leaves absorb water and nutrients well enough to benefit a plant? " Apparently, they can.

    While it was not the intention of the experiment to determine the effectiveness of foliar feeding, the best method of applying it or other variables, a couple of observations can be made. First, the differences observed were slight, and were not observable until the third or fourth week. Second, the effects of foliar feeding were observable, for the most part, on portions of the plants which developed during the experiment. Lower portions of the plants, which had developed prior to the start of foliar feeding were less affected or not affected at all.

    During the course of the experiment, some changes were made. These changes were intended to make the result, if any, more readily observable.

    In week 2, a change was made in the procedure in order to give the foliage more time in the wet condition and, therefor, more opportunity to absorb nutrients.

    At the suggestion of Jkirk,, and after a brief literature search to explore the principle involved, a small amount of epsom salt (magnesium sulfate) was added to the nutrient solution at the start of week 3. Because differences between the two groups began to appear subsequent to that change, it is tempting to attribute the changes to the epsom salt. We cannot be certain, however, because the variables associated with the foliar fed group included both epsom salt and soluble fertilizer. A follow-up experiment to evaluate the effectiveness of epsom salt would be interesting.


  • LandArc


    If you look into epsom salts used as a fertilizer, you will see that the addition of the epsom salts modifies that balance of chemicals (and thus nutrients) being applied. It is a proven contributor to some gardens. Great experiment and results. I foliar feed as we found that it could be useful in pushing plants along towards growing faster.


  • ruthieg__tx

    Wow very interesting...thanks so much for sharing all of that info...

  • ddsack

    I have been waiting for the results of your experiment with great anticipation ... thanks for all your work! I'm one that has been skeptical about the benefits of foliar feeding -- my gut feeling has always been that it makes about as much sense as smearing mashed potatoes and gravey on my arm. (Yeah, yeah, I know about various skin patches for drugs, but still ...)

    But I have to admit, that based on your photos, it does definitely seem to make a difference.

    Having said that though, I still have to wonder about any added benefits if a person is already fertilizing with solution absorbed by the roots. I notice you were very careful to not allow your foliar spray to enter the root system in the pots. I would imagine that the added growth in the foliar fed plants might be mostly attributed to the fact that the untreated plants had used up the available nutrients in their pots by the later weeks, so only the treated plants were able to extend their growing time due to the foliar supplements. This would seem to be a good thing to know, for those of us that need to hold plants in their pots a little longer than is desirable due to weather etc.

    Your experiment brings up more questions. Is there a speed limit to a plants ability to grow? Can you over-fertilize by using both foliar and root fertilizers? At what point are you just wasting your time and money, and at what point are you are actually harming the plant?

    Good thing tomatoes are such forgiving plants, fuss with them or leave them alone, you can still expect a few tomatoes at the end of the season. Thanks again!

  • jimster

    You know, I've also wondered about smearing medications on the skin to relieve muscle pain. But at least some compounds do penetrate the skin. Your example of patches shows that. I know even less about how skin is penetrated by chemicals than how it works with leaves.

    Hmm... Do you think patches would work on tomato plants? :-)


  • atillathepun

    hmmm, plant patches...the trick would have to be to see if stalks absorb like leaves do, since you wouldn't want to interfere with photosynthesis. Also, they would have to be a difficult combination of potency and slooooooow release in order for them to be efficatious. Probably too much effort/too little result.

  • marie_in_wa

    I watched this thread with interest last year, and I'm curious - if you grew them out, did you keep tabs of which was which through the growing season? If so, which produced the best?

  • treponema

    I've been foliar feeding 6 tomatoes with a very dilute solution containing Iron, Boron, Zinc, Manganese, Magnesium and Copper.I lowered the pH to keep the iron from precipitating, and added a few drops of Tween (a wetting agent.) Been doing it for about 1 1/2 months. This is definitely not a controlled experiment but the plants look great. Maybe like chicken soup - it couldn't hurt.

  • vodreaux

    Here is some more information on Foliar Feeding.


    Foliar feeding, using natural organic foliar fertilizer, is an effective method for correcting soil deficiencies and overcoming the soilÂs inability to transfer nutrients to the plant. Tests have shown that up to 90 percent of a foliar fed nutrient solution can be found in the smallest root of a plant within 60 minutes of application. A project conducted at Michigan State University, using radio­active tagged nutrients, proved that foliar feeding can be 8 to10 times more effective than soil feeding.

    The effectiveness of foliar applied nutrients is determined by (1) The condition of the leaf surface, in particular the waxy cuticle. The cuticle is only partially permeable to water and dissolved nutrients and, as a result, it can limit nutrient uptake. (2) The length of time the nutrient remains dissolved in the solution on the leaf's surface. (3) diffusion, the movement of elements from a high concentration to a low concentration. For diffusion to occur, the nutrient must dissolve. and (4) The type of formulation. Water-soluble formulations generally work better for foliar applications as they are more easily absorbed when compared to insoluble solutions. Water insoluble formulations are generally slow acting because they must dissolve before they can be absorbed and are more applicable for soil applications.

    The best time to foliar feed is late evening to early morning. These are the times when the stomata (the small opening on the leaves) are open.

    Avoid foliar spraying when Â
    Â When the temperature above 80F.
    Â When the weather is hot and dry and water vapor is leaving the cells.

    Foliar spray Â
    When the temperature is 72F or below.
    Â Early in the morning when the cells of the leaf are full of water and dew has collected on the foliage.
    Â When air temperatures and humidity both equal 135 or less.
    Â When air temperature is cooler than soil surface temperature.

    NOTE: A biological surfactant can reduce water tension and improve the absorption rate of foliar sprays.

    Where possible, the pH of a foliar spray should be between 6.2 to 7.0. To promote young plant growth a sweeter (alkaline) solution (pH 7.0) is recommended. For established growth, a more sour (acid) solution (pH 6.2) is recommended.

    An effective foliar application can produce results in 1 to 6 days. Use a refractometer to detect results.

    Here is a link that might be useful: FOLIAR APPLIED PLANT NUTRIENTS

  • jimster

    Sorry for being so slow to respond. I've been away from this forum for a while.

    I grew out only one of the plants used in the experiment and gave the others away, so I have no data on how they did later.

    In any case, as you could see from the results, the differences between plants were slight. Not an exciting result but, hey, we wanted to know the truth, didn't we.

    Most of the time, we don't have clear data. We have to go rely on our best hunches. Go for it.

    You have to be a little skeptical about statements used in promoting a product. I read the original sources for some of that blurb and did not find it as conclusive as it sounds when cited selectively. Most products produce some results when used as directed, but few, if any, are miraculous.


  • dilbert

    "one gallon of each. Solution A is distilled water with five drops of liquid detergent as a wetting agent."

    I know from experience that, at least, 0.5 tsp/gal of surfactant are needed for thorough coverage. You need to use a nonionic surfactant. Household detergents are partially ionic and often contain chelating agents which bond with some ions, particularly Ca+2 and Mg+2. There are surfactants made for foliar sprays, e.g., see http://rosecare1.stores.yahoo.net/adjuvants.html.

    The silicone based surfactants, Kinetic and Silwet L77, are reputed to be the best for tranferring other solutes into the plant, but, I worry about biodegradability within the plant. Although I haven't tried it, N-90 was recommended to me. Personally, I have had good success with Triton X-100, which is NOT registered for horticultural use.

    It may interested you to know that urea has biological effects on plants that are not related to its nutritional value. It is well known that urea penetrates leaf surfaces faster than most other substances. I have been told that it causes leaf stomata to open. I have personally observed that a large dose of urea temporarily stops a plant from growing but, after 1-2 weeks, there is a sudden burst of growth and the plant more than catches up with the controls.

    "The most widely agreed upon benefit of foliar feeding is that nutrients can more quickly reach all parts of the plant than by root feeding."

    Maybe, NPK, but not some other elements such as boron. Foliar fed B never reaches roots. Also, it may interest you to know that some growth regulators such as ancymidol are almost completely ineffective as sprays.

  • jimster

    Thanks for the interesting information. If I were to carry this further and attempt to optimize a foliar plant food, that sort of knowledge would be very useful. As it was, my only goal was to find out, through first hand observation, if plants can absorb nutrients through their leaves.


  • digdirt2

    bump - Now that I found this it's too good to lose Jim. :)

  • billtex


  • jimster

    Hey, it's still here.

    Maybe it's time for another experiment. I'm thinking.


  • protea_king

    Hi Jim, I read somewhere that tomatoes don't like water on their foliage, which is why its recommended that you water from below not overhead. Did you notice any adverse effects of the application of water onto the foliage of your tomatoes in your experiment?

  • iamgrowerman

    Foliar feeding works wonders if you do it right.

    The reason plants don't like water on their leaves is the way light refracts through droplets of water. Basically each drop of water acts like a magnifying glass, concentrating the sun's rays onto a small spot of the plant's leaves, burning them.

    This is why surfactants are so important to foliar feeding. They break the surface tension of water so that it won't form droplets and instead spreads smoothly over the surface of whatever it's on. Soap is a good example of a surfactant.

    IMHO you want to use something a little more purpose-built for the task than soap if it's for a plant you eat. I wouldn't want to put soap on my salad so I won't spray it on my plants either. I've heard really good things about Organic Wet Betty. Advanced Nutrients makes it and it's all organic to boot.

  • cyrus_gardner

    Great experiment GIMSTER

    I have a few observation, regarding actual foliar feeding and your experimental method.
    1- In actual foliar feeding, inevitably part of the sprayed on nutrients fall on the soil and eventually get into the root system. That is to say that in reality and practice there can be no pure foliar feeding.

    Experiment of Pure foliar feeding can make better sense if it is compared to no feeding at all. This way it can more clearly determine the effectiveness of foliar absorption.

    2- If I had the opportunity, would run a similar experiment,
    adding a third and fourth groups:

    Third group will get no feeding, just watere.
    Fourth group will allow the nutrient fall of the leaves onto the soil. This is fair as long as the amount of nutient soution fed is equal to that of root-fed group.
    For the gardener or farmer the end result is what it counts.And in the real world there can be no pure foliar feeding.

    Final Note:
    I have heard alot about foliar feed with epson salt. I have heard those who swear by it. This year I am going to conduct my own semi-scientific experiment in my garden lab.
    I am going to do it on peppers and tomatoes.

    Another point to consider, about any feeding, is the productivity. Greener tomato or pepper bush may not mean more productivity. But it may have some value for the vegetables which ther greens are consumed.

  • knowboddy

    One thing you might want to consider in your foliar fertilizer experiment is the addition of something like Wet Betty by Advanced Nutrients.

    It's specially designed for this kind of thing. According to the label it combines surfactants and a bunch of other stuff to promote growth. Seems like it would be a good foliar fertilizer to compare with the other known benchmarks.

  • struwwelpeter

    In my experience, the best surfactant is Triton X-100. Usually, 1/2 tsp/gal is sufficient to prevent beading on glossy leaf surfaces.


    sold relatively cheap at:


  • albert_135   39.17°N 119.76°W 4695ft.

    Below is a link to some serious, howbeit readable, material on foliar feeding.

    Here is a link that might be useful: foliar feeding

  • KatyaKatya

    Very interesting, so comprehensive, thread continued over several years...
    I found that the benefits of foliar feeding where I live are outweighed by the wet climate. The less moisture on leaves here, the better, regardless. It encourages mold and rot, even with good air circulation.

  • jimster

    Here is a post from the Vegetable Growing Forum:

    Posted by Edymnion z7 (My Page) on Mon, Dec 31, 12 at 16:06

    Hey Jim, I have a question about your foliar feeding experiment.
    I read where you were careful not to let the foliar feed drip into the soil, but (and maybe I just overlooked it), I don't see anywhere that you said you were giving the non-foliar plants the same additional food through the roots?

    From my experience, the question isn't "Can plants absorb water and nutrients through the leaves", but "Is foliar feeding more effective than simply pouring it directly into the soil?"

    I mean, if both sets of plants are treated the same otherwise, and one is getting additional feeding, it seems rather straight forward that it would do better. The real question is efficiency. If both plants receive the same amount of feeding, only one gets it only on the leaves and the other gets it only on the roots, which one will do better?

  • jimster

    "I read where you were careful not to let the foliar feed drip into the soil, but (and maybe I just overlooked it), I don't see anywhere that you said you were giving the non-foliar plants the same additional food through the roots?"

    I am embarrassed to discover that I neglected to include that information in my report. Not that it would have affected the results but, for the sake of completeness, it should have been included.

    I do not remember if I provided any nutrition to the roots beyond what was in the seed starting mix; ProMix BX. My normal practice with seedlings is to start giving them a weak solution of fish emulsion when they have two sets of true leaves. This is what I would have done if I provided any root feeding and I would have done it to both groups. However, I suspect that the only feeding I gave in this experiment was to the foliar fed group.

    "From my experience, the question isn't "Can plants absorb water and nutrients through the leaves", but "Is foliar feeding more effective than simply pouring it directly into the soil?"

    That is one of several questions posed by readers. But, as you correctly understood, the one and only question I was attempting to settle was whether plants can absorb useful amounts of soluble nutrients through their leaves.

    Once again, I encourage other gardeners to undertake experiments to satisfy their curiosity about various gardening topics. I assure you it's a fun, inexpensive and satisfying activity.


  • growneat


    This thread is so good I thought I would bring it back for another go around. Marv

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