Fertilizers play an important role in the health and growth of plants, as they are soil amendments that supplement the nutrients missing in the soil. Although roots are responsible for the plants’ ability to absorb nutrients, there are other ways that a plant may take in what they need.
You can spray fertilizer onto your plant leaves, and the additional minerals are immediately available for your plant to use. This method of spraying fertilizer on the plant leaves is known as foliar feeding and is an excellent way to temporarily correct nutrient deficiencies in plants.
In this article, I’ll explore whether plants can absorb nutrients through their leaves and dive deep into the technique of foliar fertilization. I’ll also look at which plants benefit from foliar fertilization and what to consider beforehand, so read on!
Can Plants Absorb Fertilizer Through Their Leaves?
Plants can absorb fertilizer through their leaves. According to research, plants can absorb minerals through the leaf cuticle through the minute pores present on the leaf’s surface. The pores are charged to attract the molecule of macro and micro plant nutrients.
The pores on the cuticle of plant leaves are negatively charged, attracting the positively charged molecules of elements like calcium and magnesium, which are plant micronutrients. Macronutrients like nitrogen and potassium also have positively charged molecules, so they can also be absorbed through the leaf cuticle.
Not all nutrients are easily absorbed through the leaves, however. For example, phosphorus and sulfur have negatively-charged molecules, meaning they find it difficult to enter through the negatively charged pores of the leaf cuticle. Even after absorption, nutrients with large molecules like calcium won’t move easily through the plant and are hard for the leaf to break down.
Therefore, the process of fertilization through the leaves should be undertaken very carefully. It’s important to assess how urgent the need is, whether the nutrient will be absorbed easily by the leaves and how it’ll move once it is absorbed.
The leaves are where the nutrients are processed, so they can’t absorb too much fertilizer in one go. When fertilizer is absorbed from the roots, the nutrients have to travel to the leaves so that more can be taken in.
In contrast, applying fertilizer directly to the leaves ‘fills up’ the leaves with nutrients, so to speak, so only a little can be applied and absorbed by the leaves at a time.
Understanding Foliar Fertilization and When It Is Used
Foliar fertilization or foliar feeding is a method in which fertilizer is applied directly to the leaves of a plant or the blades of grass on a lawn.
Applying fertilizer to the leaves of plants is, in some ways, an easier way of addressing nutrient deficiencies in plants, as the nutrients are more easily absorbed by the plant. As the nutrients don’t need to move through the plant to reach the leaves, they’re more immediately available for the plant’s use.
These fertilizers often take effect immediately and are useful when you notice a nutrient deficiency in your plants. The foliar feeding method is especially useful for nitrogen or potassium deficiencies in plants and is often used to supply nitrogen quickly to plants.
However, foliar feeding is not a long-term solution or replacement for fertilizing the soil. You can use the foliar feeding method to supplement your plants until you get your hands on your fast-release fertilizer of choice or as you wait for your slow-release fertilizers to work.
Foliar feeding can be a way to supplement recently repotted plants as a way of supplying them with starter solutions, but it shouldn’t be used on seedlings with fragile leaves since they wouldn’t be able to absorb the nutrients easily (if at all).
What Plants Benefit From Foliar Fertilizer?
Vegetables, crops, and ornamental plants benefit from foliar fertilizer in particular, as these plants need additional nitrogen and potassium to produce their flowers and fruits. Producing vegetables and fruits use up a significant amount of nutrients in these plants, so foliar feeding is helpful.
In other words, foliar feeding can be applied to just about any plant with leaves and helps improve overall plant growth.
Any plant that has to produce flowers and fruits uses up a significant amount of the plant macronutrients of nitrogen, phosphorus, and potassium in the process. These nutrients are quickly depleted in soils, and soil-applied fertilizer takes time to work.
To ensure that plants receive the nutrients when they need them (right as they’re flowering or fruiting), you can feed the plants by spraying foliar fertilizer directly onto their leaves. This method will also ensure that the plants have immediate access to the nutrients they need, and they can continue flowering or fruiting uninterrupted.
How Long Does a Foliar Spray Take to Work?
Foliar feeding should be undertaken carefully, as and when necessary. It’s a great way of addressing nutrient deficiencies quickly as up to 60% of the applied nutrients are absorbed within 24 hours. The effects take a little longer than that, though.
A foliar spray that is applied correctly takes as little as 48 hours to work, and should show results within a few days. The only time the foliar sprays do not show any improvements in your plants is when they have been washed off by rains or if you have used too much and scorched the leaves.
As with all fertilizers, you must water your plants well to ensure that they have the water they need to absorb nutrients.
Inorganic fertilizers contain mineral salts, and if the concentration of salts outside plant tissue is greater, they will draw water out of the plant. The leaves will lose water, leading to wilting, yellowing, or browning, which will kill the leaf and affect your plant’s health due to fertilizer burn.
When Should You Not Foliar Feed?
You should not foliar feed your plants on very hot days when plants are likely to be dehydrated. On hot, dry days, the fertilizer will evaporate, leading to nutrient loss. You also should not foliar feed before rain as the rain will wash the fertilizer away, and it will need to be reapplied.
Foliar feeding is a great way to supplement your plants’ nutrient needs when they’re growing, but nutrient deficiencies are easier to address than fertilizer burn. When applying fertilizer through the leaves, you have to take care to use a diluted solution in small amounts to ensure you don’t burn the plants.
Applying fertilizer during the rains is a good idea only if you can keep track of the weather and fertilize when the humidity is high, and you have at least two days until it rains again.
Fertilizing right after the rain and a minimum of two days before the next one is the best time to feed your plants through foliar feeding.
Things to Consider Before Applying Foliar Fertilizer
Foliar fertilizer has many benefits, and you can keep your plants healthier by keeping the following things in mind before applying foliar fertilizer:
The Degree of Nutrient Absorption
As discussed earlier, not all nutrients are absorbed easily through the leaf pores. Potassium and nitrogen will be absorbed easily, but not nutrients like phosphorus. Additionally, absorbed nutrients like calcium may not be used once absorbed.
The Concentration of Nutrients
Fertilizers applied to the leaves need to have a high nutrient concentration to address any deficiencies. But they also can’t be too strong, or the mineral salts will burn the leaves. It’s always better to dilute the fertilizer first.
You can always add more fertilizer later, but you can’t undo leaf scorch.
Applying foliar fertilizer is only affordable if you’re applying it infrequently. Sustained application of foliar fertilizer can become quite expensive and damage your plants, so consider your plants’ needs and what you can afford.
Other Avenues of Fertilization
Foliar fertilizer should always be used to supplement your plants’ nutrient needs and shouldn’t be the primary nutrient source. If you notice a nutrient deficiency, you can use foliar fertilizer to correct it temporarily.
In the meantime, you should apply slow-release or organic fertilizers to support your plants.
The environmental factors need to line up to support foliar feeding. There should be light, but the sun can’t be too hot, or you’ll burn your plants. High winds can lead to leaf scorch as well. The humidity needs to be just right to prevent runoff.
The Surfactants You’re Using
Surfactants ensure that the fertilizer is distributed evenly over the leaf. Your surfactant should cover the leaf completely and not damage the leaf in any way. A silicon-based surfactant is ideal.
You can spray fertilizer directly onto your plant leaves to supplement their nutrient needs. This method of fertilizer application is called foliar feeding or foliar fertilization and is a great way to address plant nutrient deficiencies temporarily.
Plants that need to yield flowers or fruits particularly benefit from foliar feeding, but it must be done carefully to prevent leaf scorch. Foliar feeding cannot be the primary avenue of fertilization for any plant. Instead, it only supplements existing fertilization systems.