Learn how to turn your backyard into a food forest in three steps in this article, video and podcast.
Healthy fruit trees will produce an abundance of delicious, fresh fruit. But not all fruit trees are healthy. When a fruit tree is weak, it will struggle. It will experience common fruit tree pest and disease problems and produce poor quality fruit. So the grower's job is to work to improve fruit tree health and one of the best ways to do this is to use a well-designed homemade fruit tree spray.
In this interview, regenerative agriculture expert John Kempf explains how homemade fruit tree sprays can boost tree healthy by increasing their ability to produce energy through photosynthesis. With this extra energy, your tree can grow faster, produce better quality fruit and fight pests and diseases.
This is an excerpt from an hour-long interview with Susan Poizner of the fruit tree care education website OrchardPeople.com. The entire interview and a shortened video excerpt can be found below.
JK: The purpose of regenerative agriculture is to regenerate the health of overall ecosystems. We want to regenerate soil health and plant health, so that they're completely resistant to insects and diseases. And ultimately, to have a regenerative impact on human health as well. Plants are the engine that drive that entire system, because through the process of photosynthesis and collecting sunlight energy, the plants bring new energy into the system. The impact that foliar sprays (ie. sprays that are used on the leaves of a tree) can have, is that they can dramatically increase the plant's capacity for photosynthesis.
JK: So what we have come to perceive as being normal, is plants that are only photosynthesizing somewhere in the neighborhood of 15 to 20% of their inherent genetic photosynthetic capacity. So that means that these plants are only producing a fraction of the sugars that they're really capable of. Foliar sprays, when properly designed, can dramatically increase that by two or three or four times, which allows the plants to produce a lot more sugars. That will put more sugar into the soil system, regenerate soil health, build organic matter, and sequester carbon, Ultimately, this regenerates soil microbial populations and improves plant health and disease and insect resistance.
So from my perspective, foliar sprays are the jet fuel that accelerates the entire system. They are not something that we need to be dependent on for the long-term. But in the short-term, they really accelerate the system and speed it up to a much higher plateau of performance.
JK: To some degree, the plant can select which nutrients it absorbs from the soil. But when you are putting on a foliar spray, you're not giving the plant much of a choice. And so, if you spray nutrients that the plant already has adequate or abundant levels of, you are not likely to produce a significant plant response. But if you design your spray to include the nutrients that plants require to increase photosynthesis, you can produce a tremendous plant response. So, design targeted to specific outcomes becomes much more important than it does for soil applications.
JK: I'll go straight to the magical shortlist of five nutrients. They are magnesium, manganese, iron, nitrogen, and then a bonus fifth element on the list is phosphorus. Now each of those first four nutrients that I mentioned are directly involved in the photosynthesis process.
Magnesium is the center ion of the chlorophyll molecule. Iron is needed to put chlorophyll together although it's not a part of that molecule. Nitrogen is a part of the chlorophyll molecule surrounding magnesium, and manganese is responsible for water hydrolysis. So even if you have perfect sunlight, perfect water, perfect carbon dioxide and abundant levels of chlorophyll, if you don't have enough manganese, then that will limit the plant's photosynthesis potential. And I am pointing this out and emphasizing it specifically, because our crops are almost universally deficient in manganese today, because of the way that we have mismanaged our soil for the last couple of centuries, and also because of the almost ubiquitous presence of glyphosate in our environment.
JK: The brief answer is that whenever you get it done, it's going to produce a crop response. And when you don't get it done, then there are no particularly negative consequences. This is a different approach than thinking about applying insecticides or fungicides. We're not trying to time everything specifically so that we kill certain organisms, but instead, we're taking a more general approach of increasing the overall system health, which is something that we can do at any time.
JK: So there are several mechanisms that have been described for plants absorbing nutrients. They can just dissolve across the stomata or across the leaf cuticle and be absorbed directly by cells depending on which products and the forms that you are applying. But I think one of the most important and most valuable mechanisms is the biology that lives on the microbiome on the leaf surface. The microbes absorb the nutrients that are in the foliar spray, and then they transfer the nutrients into the plant. Because the biology on the leaf surface has a symbiotic relationship with the plant much the same way that the biology does that is on the root surface. (Editor: Learn about the role of microbes in feeding fruit trees in this article)
JK: In our own digestive system or the digestive system of any healthy animal, we have symbiotic organisms that digest our food and make it available to us, and the same is true of plants. The reality is that healthy plants absorb upwards of 80% of all their total nutrients from both soil and atmosphere through biology. So not directly, but indirectly.
JK: The answer is yes, yes and yes. Kelp, you want to make sure that the particle size is small enough that you don't clog your sprayer. Fish emulsion, you want to make sure that none of the neighbors are within smelling distance. But aside from that, those would be great ideas.
Herbal tea is a great idea as well. Is actually a great probiotic. Herbal extracts can influence plant health positively in much the same way that they can influence human health positively.
Many of these herbs also have unique microbial populations on the final plane on the leaf surface. So take yarrow, for example. Yarrow has one of the most diverse microbiomes on the leaf surface that is known with over 600 species that have been identified so far. So it's possible that the effects of using herbal teas as foliar sprays may be coming from some of the compounds these plants contain. It's also possible that they may be coming from the microbial populations on the leaf surface themselves. We don't really know.
JK: Well, first of all, you should never apply Coca-Cola directly undiluted to a tree, because obviously, it's too acidic, it's too corrosive for the same reason it cleans battery acids. So it always needs to be diluted at a rate of approximately four to six ounces per gallon of water diluted and sprayed on. The reason I recommended Coke as a possibility, is thinking of materials that can have a beneficial impact on plant health that we have at home already. And Coca-Cola is one that fits that category. Because it is a form of leaf digestible sugar and phosphorus. And phosphorus is very often one of the limiting factors that really limits plants development, particularly in urban and urban environments, and plants respond very positively to it.
How long will it take for a plant to absorb a foliar spray with Coca-Cola? Will it make the tree leaves sticky and attract ants?
When you have plants that are healthy, they're green, they're photosynthesizing. If you apply any form of sugar on that plant, it is likely to be absorbed into the plant in a matter of hours. Usually, at the very outside, if you have challenging environmental conditions, it might be a maximum of six to eight hours, it'll usually be two to three hours. So there will be no stickiness on a living green plant.
JK: You can use any type of sprayer, you just have to be cautious to ensure the materials you're using are not going to clog sprayer nozzles. As a rule of thumb, you want to avoid putting on concentrations of any material greater than eight ounces per gallon, because you have the potential of burning leaves if you over-apply. And the intention also is to mist on the leaves a very light coating of droplets. You are not spraying the leaves until the leaves are wet to the point of dripping off. So the intention is just a very light mist, very rapid once over, and at fairly dilute concentrations.
JK: Yes, plants do not have the option of rejecting what you apply. So they cannot be selective like they can in soil. So that means we need to be very cautious about not over applying. And this is a very important point, because many of the disease challenges and insect challenges that our plants are susceptible to are a result of the excesses of nutrients that are applied and not the deficiencies.
JK: The greatest crop responses are usually produced from applications, either very early in the morning well, before 8:00 AM or in the evening. And many people for practicality prefer to apply it in late evening.
JK: It depends on the results you want to get. You can apply them as infrequently as once every three to four weeks and still expect to see some nice crop responses. Or if you want some extraordinary crop responses, we actually have some commercial growers who are farming on a scale of hundreds of acres. There's one that I have in mind right now that applies every 48 hours. And with that frequency of application, he's been able to triple the average yields of apples in Washington. But when you increase the application frequency, then you need to correspond that by putting on lower concentrations each time you apply.
JK: I think perhaps one of my most favorite recommendations would be to use live culture yogurt or kefir or any type of lactobacillus culture as a foliar spray. Again, at a rate of about two to four ounces fixed into a gallon of water. This is a very effective tool, particularly to prevent the infection of bacterial diseases.
So I first came across this as an idea in our small home orchard where we had a dozen or so peach trees, where we had this invasion of peach leaf curl that became a tremendous problem. And I was thinking about what I might be able to use very quickly that I might have at home, and I came up with the idea of using yogurt. So we made our own homemade yogurt, I put on a foliar spray of yogurt once every four days for three or four applications, because the trees were very badly infected. The infection completely cleared up and peach leaf curl disappeared.
And we've now repeated that experience any number of times on different orchards including even commercial orchards, because that is one of the diseases for which there is not really any effective treatment organically. And it just so happens that this treatment is very effective, and it's easy. And its effectiveness comes about as a result of recolonizing the leaf surface with healthy bacteria and essentially outcompeting those that could be potential pathogens.
JK: Apple cider vinegar is an interesting compound. And it might be more relevant for vegetable production and for tree food production. First of all, it is a probiotic and a prebiotic, similar to yogurt. It will enhance microbial populations on the leaf surface, which can be very valuable. But it contains acetic acid. If you apply it again and rates in the neighborhood of two to four ounces per gallon of solution, it can actually trigger bud development of reproductive buds. So if you have a plant or a tree that is not setting flowers and isn't flowering, you need to know when the timing is for when that particular species sets buds. For many fruit trees, the reproductive buds are actually set the year prior. So for cherries and apples, for example, the buds would often be set in the June, July time periods when bud initiation happens for next year's crop.
So at those periods of time when we have the bud initiation, putting on a foliar application of apple cider vinegar can actually trigger bud initiation and bud development. So if we have a tree that isn't flowering, isn't reproducing, that can be a very useful tool. The same is also true of vegetable plants. If we have tomato plants that are six feet tall and lush green with lots of foliage but not a single tomato, putting on foliar applications of apple cider vinegar can help switch that.
JK: I don't have enough experience that I have a qualified opinion. Obviously, it would depend on the concentration of the herbal tea and so forth. But if you want to dig deeper into that topic, I highly recommend a book that I wrote the foreword for. It's authored by Nigel Palmer (The Regenerative Grower's Guide to Garden Amendments: Using Locally Sourced Materials to Make Mineral and Biological Extracts and Ferments) He's done some really interesting research that brings together lots of these different microbial culturing modalities into one integrated whole.
JK: Blackstrap molasses can be particularly valuable because it is a good source of iron. And it's really interesting. There are three different nutrients which will turn plants dark green. Those are nitrogen, magnesium, and iron. And each of those three contributes to the development of chlorophyll and increases chlorophyll concentrations, which of course, allows leaves to intercept more sunlight and photosynthesize more successfully.
The greatest crop responses come about as a result of a balance of all three of those. So it's common in conventional agriculture, for example, to over-apply nitrogen, but not to address magnesium and iron to correspond. So if we address all three of those at the same time, we will produce the greatest crop responses. So blackstrap molasses can be a great source of iron. And then to address the magnesium component, I would suggest Epsom salts. I'm a fan of Epsom salts and I think it should be in every foliar spray at low doses. So somewhere in the neighborhood of a half an ounce of the crystals per gallon of water should be a part of every foliar spray because of the impact that it has on plant health and improving photosynthesis.
JK: Mixing works incredibly well. Combinations are much more effective than individual products by themselves. The only caution that I mentioned back at the beginning, is to avoid a total of all the ingredients greater than eight ounces per gallon. Anything less than that, you should be fine. And greater than that, you have the potential for leaf burning.
JK: So I mentioned that the three nutrients which increase chlorophyll are magnesium, nitrogen, and iron. We addressed magnesium and iron, we haven't yet talked about nitrogen. And whey protein can actually be a great source of nitrogen. Commonly in agriculture when we think about nitrogen applications, immediately our thoughts go to various nitrogen products like a Miracle-Gro fertilizer or 20-20-20 or calcium nitrate or whatever the case might be. The challenge is that those mineral forms of nitrogen, either ammonium or urea or nitrate, all have significant negative health consequences for plants. They tremendously increase disease susceptibility and insect susceptibility. Amino acid nitrogen or protein nitrogen does not have those negative side effects. So putting whey protein into a sprayer and applying it can be a way to supply nitrogen and to supply protein to the crop without having the negative effects of a water soluble fertilizer.
JK: You can get whey protein... I'm imagining athletes drinking protein shakes. So I think anywhere you would get a protein shake, you can get whey protein. You could also use milk. If you want to, just use milk or powdered milk to provide proteins and fats and a little bit of calcium as well. It's less concentrated than it would be in a whey protein, but there will still be some nitrogen value there for sure.
Interested in learning more about fruit tree sprays? Check out our article on when to spray apple trees to protect them from pests and diseases and how to use holistic fruit tree sprays. To learn more about feeding fruit trees, check out our article on when to fertilize fruit trees. Looking for a great quality pressure sprayer? This backpack sprayer (affiliate link) is our favourite.
Susan Poizner is an urban orchardist in Toronto, Canada and the author of Grow Fruit Trees Fast and Growing Urban Orchards. Susan trains new growers worldwide through her award-winning fruit tree care training program at Orchardpeople.com. Susan is also the host of The Urban Forestry Radio Show and Podcast and an ISA Certified Arborist.
This page includes affiliate links. Orchard People may receive a small commission if you make a purchase. The funds will help support the creation of free resources including our blog, YouTube channel and podcast.