Let’s start at the beginning:

Foliar feeding has been used to provide nutrients to plants by traditional farmers since the 1920’s. In the 1950’s, two professors at Michigan State University, H. B. Tukey and S.H. Wittwer, proved conclusively that foliar feeding is effective. Radioactive phosphorus and potassium were applied to leaves. A Geiger counter was used to measure absorption, movement and nutrient utilization. The rate of movement through all parts of the plant was one foot per hour.

So, it’s proven to work but why should you, a hydroponic grower, use it?

Thanks for asking!

What is foliar feeding?

Foliar feeding provides nutrients to plants through its leaves and stems, not its root. Nutrients are sprayed on the leaves and stems and are absorbed by stomata, the epidermis and bark of woody plants. The nutrients move from the place of absorption throughout the entire plant, including the roots, within one day. Referencing the professors above, it’s about a foot an hour.

Foliar feeding is an alternative to root feeding. It’s another method to get nutrients into a plants transport system. Foliar feeding works with gravity (from the top of the plant down) instead of against gravity (from the roots to the top).

Why should I foliar feed?

Foliar feeding provides fast absorption of nutrients- results can be almost immediate. It’s 8-20 times more effective than root feeding. Foliar Feeding is not just a quick fix for deficiencies. Provide additional nutrients to increase yield and quality. Micronutrients, calcium and supplemental fertilizer are often applied to plants through foliar feeding. With most plants, foliar feeding augments- not replaces- a standard root feeding program.

Foliar feeding is easy. Nutrients and a sprayer are all the equipment needed.

When should I foliar feed?

Clone stage
Foliar feeding is the most effective method of providing nutrients to clones as they aren’t rooted. Clones need nutrients to develop roots and prevent yellowing of leaves.
To increase yield and quality
Provide plants extra nutrients to increase yield and improve quality

  • Cheaper than CO2 generator
  • Doesn’t replace standard root feeding
Overcome deficiencies
Even well managed hydro systems can become nutrient deficient because:

  • Nutrients cannot be absorbed
  • There is opposition between nutrients
  • Nutrient balance is not optimal
  • pH level is too high or low
  • Nutrient solution is too hot or cold
  • Media does not hold nutrients or water
  • There is oxygen deficiency at the roots
Plant under stress
Foliar feeding can revive plants under stress from

  • Not enough nutrients
  • High or low humidity
  • Lack of light
  • Temperature stress, hot or cold
Damaged roots or death
Root damage can be caused by disease, pests, too much water. Plant diseases on roots can cause deficiencies that are not obvious.

How do I foliar feed?

  • Mix product exactly according to manufacturer’s recommendations (read the label!).
  • Test product on one plant before treating an entire crop.
  • Use a sprayer with a fine mist.
  • Spray the top and underside of leaves.
  • Spray until leaves are very wet or there is a very slight run off.
  • Spray with lights off. Leave them off until leaves are dry.
  • Use a non-ionic wetting agent to improve absorption.
  • Spray weekly on annual plants.
  • With cannabis, spray from cone through vegetative stage, then one to two weeks into blooming.
Spray-N-Grow Scientific Research

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