The planting and growth of fruit trees, shade trees, shrubs, and many other landscape plants benefit from a foliar feeding of nutrients. Liquid biochar blend products contain all the micronutrients necessary for lush growth and abundant fruiting, with the added benefits of water retention and increased beneficial microbial activity.
As you’re adding that tree, shrub, or garden space this year, consider how resilient your planting would be with the addition of charged biochar. How does a natural nutrient spray work, and how is it better than a synthetic fertilizer?
Key points
- Plants' roots take up nutrients, but that’s only half the story
- Applying nutrients results in healthier crops than fighting off pests and diseases with synthetics
- Leaf surfaces are active sites for beneficial microbes, nutrients, and moisture
- When you foliar feed micronutrients, you avoid nutrient tie-ups in the soil
- Foliar feeding macronutrients is complicated and often leads to nutrient excesses
- Biochar increases the effectiveness of foliar feeding micronutrients
- Foliar spray of a biochar blend shifts the tree-planting mindset from “what’s underfoot” to “what surrounds and protects.” It’s a canopy-level commitment to sustainability, one that acknowledges the entire physiology of the plant.
Learn how VITAL Blend 5M can be used with your existing spray protocol for increased tree health
Rethinking the Roots of Growth
For many years, we’ve been taught that plants gather nutrients such as nitrogen, phosphorus, potassium, and micronutrients through their roots. That is true, but it’s only half the story.
Leaves gather nutrients and moisture and are a haven for beneficial microbes. The science behind foliar feeding isn’t all that complicated once you think about it. Think of a leaf as a grouping of skin tissue. Just like our skin, plant leaves breathe. They breathe out oxygen and breathe in carbon dioxide. Much more happens during that “breathing” process than just the exchange of gases.
Foliar feeding is gaining traction for numerous reasons. One is that ag tech, in the shape of drones, is making spray applications of nutrients easier. We’re also learning that spraying nutrients on plant leaves is far more effective for optimum plant health than spraying fungicides and pesticides.
The “ides” kill the pathogens, but they also wipe out the beneficial microbes that stand guard against those pathogens. We make our trees and shrubs more susceptible to the next outbreak. Foliar feeding means healthier trees, more beneficial microbes, and an improved bottom line.
The Science of Foliar Feeding
There are two ways a plant can gain nutrients through a foliar spray. One is when the stomata, microscopic pores on leaves, open to exchange gases. The other is through the cuticular pathway. In other words, the nutrients are so small (in ionic form) that they can penetrate through the plant’s cuticle cells.
The Cuticular and Stomatal Pathways for Nutrient Absorption
The cuticle is the waxy outer layer of a leaf. This layer is thicker in some plants than others, and the healthier the plant, the thicker the cuticle. That’s both positive and negative for a nutrient spray program.
That thick cuticle acts as a physical and biochemical shield against pathogens, pests, water loss, and UV damage. It’s also a gatekeeper, and non-chelated or larger molecules of nutrients have a hard time passing through the cuticle.
The upside is that if your plants have a rugged, thick cuticle, they are very healthy and probably need fewer nutrients in the first place. Organic acids, urea, and chelated minerals can pass through the thick waxy cuticle and get absorbed into the leaf’s upper layers. For trees under stress or growing in degraded soils, the health of the cuticle is an indication of the tree’s overall resilience.
The stomata are the other way foliar-sprayed nutrients can enter the plant. On the undersides of leaves are microscopic pores that open and close, exchanging gas. These are the stomata. They are most active in the morning and evening. During the heat of the day, they often stay closed to conserve water in the plant structure.
But there is a tradeoff; photosynthesis is slowed down when CO2 uptake drops. Keeping hydrated is crucial for plants, and when they don’t get enough water, a plant will decide which part has to go to maintain long-term life. Often, a fruit tree will abort the fruit to give more energy to the roots and main structure. It can fruit another year, but if the roots die, there isn’t another year.
Knowing about the stomata rhythm makes your spray schedule more efficient. Mornings are best to spray highly soluble, readily absorbed micronutrients. Micronutrients are more effectively taken up by a plant from a foliar spray. When they are incorporated into soil as a drench, other nutrients bond with them and make them unavailable for plant uptake.
Foliar Feeding Micronutrients for Optimum Plant Growth
Common lock-up mechanisms in the soil for micronutrients include an excess of phosphorus. It interacts with zinc, iron, and manganese to decrease the amount of micronutrient ions available for plant nutrition. An excess of calcium (Ca) or magnesium (Mg) will result in a competition for uptake sites on the plant; Ca and Mg win out over other micronutrients.
These issues don’t exist with a foliar micronutrient spray. You can quickly regain plant health with these micronutrients when applied with a hand sprayer, drone, or other aerial applicator.
- Zinc (Zn²⁺): Crucial for enzyme activation and auxin synthesis. Great for early growth stages.
- Manganese (Mn²⁺): Supports photosynthesis and nitrogen metabolism. Especially helpful in high pH soils where it’s often locked out.
- Iron (Fe²⁺/Fe³⁺): Vital for chlorophyll production. Chelated forms (like Fe-EDTA) are best for foliar use.
- Copper (Cu²⁺): Important for reproductive growth and lignin synthesis.
- Boron (B): Enhances cell wall strength and sugar transport—often applied as boric acid or boron ethanolamine.
- Molybdenum (Mo): Supports nitrogen fixation and nitrate reduction.
You can also spray macronutrients (we know them as NPK and Ca), but they must be in the proper form to be effective. And before you foliar spray macronutrients, think about whether you should. They’re called “macros” because a lot is needed, and foliar absorption is limited by leaf surface, cuticle thickness, and environmental conditions.
A foliar spray program for macronutrients does not replace a good program for soil nutrition. But what could go wrong with a foliar feeding program that incorporates macros and micronutrients? A lot!
Do you want to know more about foliar nutrient applications? Click here!
What Can Go Wrong with Foliar Feeding Macronutrients?
Phytotoxicity can occur with an overconcentration, especially with calcium or potassium. Burned leaves are your indication to back off the macros.
Macronutrients also tend to bind up micronutrients and make them unavailable to plants or microbes. This is called “nutrient antagonism” and is a biochemical turf war. When one nutrient is in excess, it can block or suppress the uptake of another. Classic examples are nitrogen blocking potassium and calcium uptake, potassium messing with magnesium and calcium absorption, or phosphorus reducing the availability of zinc, iron, and copper.
Macronutrient excesses, especially nitrogen and phosphorus, are common in urban and suburban landscapes. The question isn’t whether you should foliar spray nitrogen or phosphorus, but how you can make the nutrients already in your soil available to plants.
While deficiencies do occur, especially in sandy or compacted soils, excess is often the silent cause of poor tree or shrub performance. There are ways to buffer or rebalance the nutrient dynamics in your landscape setting for more resilient and productive trees, shrubs, and lawns.
Micronized Biochar: Resilience in a Foliar Feeding
We tend to think of biochar as a granular product that we incorporate into soil. In that form, it is a habitat for microbes, a link between the microbes, nutrients, and plants, and a warehouse for minerals. But that’s not the only way biochar can benefit your trees and shrubs.
Biochar can be finely milled into particles less than 50 microns. At that minuscule size, it can be suspended in solution. It forms a stable slurry that optimizes nutrient-plant interactions. It acts as a delivery vehicle, a shield, and a signal amplifier that fortifies the tree canopy.
Those fine particles of biochar with humates cling to the leaves' surfaces and increase the time nutrients are available for plant intake. The leaf surface is called the phylloplane, and it is inhabited by beneficial microbes. When you spray micronized biochar charged with micronutrients, the microbes interact with the spray. Beneficial microbe populations become more diverse with this added food source.
The biochar provides microhabitats for the microbes that enhance their persistence and activity. The nutrient molecules are food for both microbes and the plant. Chelated nutrients such as iron and zinc bind to the biochar particles and are a slow-release fertilizer on the leaf surface.
The microbial population on a leaf is diverse and includes epiphytes (living on the surface) and endophytes (living within the leaf tissue), both benefit from the biochar foliar spray. The microbes that survive on tree leaves are tough and can handle UV exposure, desiccation, and pollutants. The foliar biochar-nutrient spray gives them fuel and habitat.
A lot is happening at the microscopic level on the surface of a leaf. Microbes are acting as biocontrol and defense and nutrients are being sucked into the plant through the cell membrane or the stomata. As long as there’s a photon of light, carbon fixation advances, and chlorophyll doesn’t take breaks. Even at night, when there’s no sunlight to drive photosynthesis, chlorophyll is maintained and synthesized in growing tissues.
Spraying Biochar Blends for a More Resilient Future
Sustainable tree planting isn’t all about what’s underfoot. It’s also about what’s at hand. Resilience is being cultivated from the top down. Leaves are not just passive solar panels. They are alive and active sites of exchange, adaptation, and growth. Biochar isn’t something buried, it’s something sprayed.
Biochar has long carried the story of transformation, of waste turned to resource. Of carbon captured and returned to Earth. But suspended in foliar sprays and carried into the canopy, biochar completes a new cycle.
- From carbon-sequestering soil sponge to
- Nutrient-carrying leaf veil.
It doesn’t just support roots, it clings to the leaf, anchors micronutrients, shields from stress, and potentially signals resilience at the cellular level.
Foliar spray of a biochar blend shifts the tree-planting mindset from “what’s underfoot” to “what surrounds and protects.” It’s a canopy-level commitment to sustainability, one that acknowledges the entire physiology of the plant, from roots to leaves, soil to sky.
Click to learn how VITAL Blend 5M will benefit your landscape this year - and into the future.
