What Is Foliar Feeding?
Well, the clue is in the name. “Foliar” means “relating to leaves or foliage”. So foliar feeding is supplying a plant with one or more nutrients through its leaves, rather than the more obvious method, through the root zone.
However, it’s important to remember that foliar feeding isn’t an alternative to root feeding. Establishing a well-developed rhizosphere through root feeding is crucial to developing healthy plants—there’s no way around that. Foliar feeding is best used when you need to boost the nutrients your plant is already absorbing through its roots by using an additional delivery method.
How Does Foliar Feeding Work?
Plants are able to absorb nutrients through their leaves via the stomata—the small pores on the underside of the leaf which they use to exchange oxygen and carbon dioxide with the atmosphere. Certain nutrients can also pass through the stomata, and be absorbed directly into the growing leaf.
The key to the process is moisture—without surface moisture, nutrient exchange is minimal. So in nature, foliar feeding happens mostly in aquatic plants, which absorb nutrients from the water in which they are growing.
Growers can create a similar environment for nutrient exchange by using a foliar feeding spray. The spray contains one or more nutrients but may also include a surfactant to wetten the leaves and improve the absorption rate.
The main benefit of foliar feeding is the speed at which nutrients are absorbed, and the direct route that they take. For example, if your plant is lacking nitrogen, causing yellowing leaves, then adding nitrogen is the answer.
Doing this through root feeding can take days or even weeks to show results—it takes time for newly absorbed nutrients to travel through the plant. With a foliar spray, you can see improvements almost immediately, as the nutrients are absorbed directly into the leaves—exactly where they’re needed.
When Should I Use Foliar Feeding?
As with any growing technique, foliar sprays are most effective when used in the appropriate situation, and in combination with general plant care. Here are a few scenarios where foliar feeding can really make a difference to the health and yield of your grow.
Maintaining Overall Plant Health
Foliar feeding strengthens every part of your plants, from leaves to the root zone. It’s ideal when plants have recovered from disease or nutrient deficiency to revive and restore them. Used alongside an effective root feeding system to optimise root health, a foliar spray ensures that your plants are receiving the right balance of nutrients—and are able to make the most of them.
Fixing Short-Term Deficiencies
Foliar sprays are a quick and simple tool to deploy when you need to treat a short-term nutrient deficiency—getting to work much faster than a formula specifically designed for root absorption.
They also allow you to target individual plants in your grow which need additional nutrients, rather than treating your entire grow at once.
But don’t rely on foliar sprays as a remedy for masking long-term deficiencies—in these cases, there’s usually a bigger issue that needs to be addressed.
Boosting The Propagation Stage
Foliar feeding is particularly effective in younger plants, so using a foliar spray on cuttings that have just rooted is a great way to give them an initial boost and encourage sustained growth.
Growers’ Tips
For the best results when using foliar feeding, check out the following tips from our in-house team of horticultural experts.
Do:
Spray the tops and bottoms of the leaves until completely covered—and excess solution visibly runs off.
Spray plants around once to twice per week—check grow guides to be sure.
Use in conjunction with your routine growing schedule—don’t foliar feed only.
Don’t use foliar feed:
In high temperatures—anything above 30ºC is too high.
During the flowering stage—it’s best during the vegetative stage.
If humidity is already too high or you’re trying to reduce humidity
Without checking grow guides—some formulas are incompatible with others.
Getting Started With Foliar Feeding
If you’re new to foliar feeding, we’d recommend you try Evolution 2.0 to get started, as it’s a strong all-around foliar spray. It’s easy to use, but also popular with many of our more experienced growers as a solid product to keep on standby for any emergencies.
Evolution 2.0 is a blend of four natural products— catalyst, veg boost, biowetter and wetting agent—all in one easy-to-apply pH-neutral spray with no need for mixing or adjustment. It’s optimally formulated so your plants get the right amount of nutrients, but in a more dilute solution than you’d use for root feeding—avoiding the risk of nutrient burn on the leaves.
The misting nozzle ensures an even distribution of nutrients onto the leaf surface, which increases the speed and volume of nutrient uptake. Additionally, the proprietary wetting agent reduces the surface tension of the solution—increasing absorption and further minimising the risk of leaf burning due to artificial lighting.