Foliar Feeding Tips & Techniques

© 2021 – James B. Kennard

1. Stomata are openings on a plant’s leaves, similar to pores on human bodies.  Plants can absorb additives and nutrients through both the stomata, on the under-side of the leaf as well as through their waxy cuticle layer, on the upper side of the leaf. Therefore, be sure to spray both sides of the leaves, and the stems. Full Coverage will assure you receive the greatest and quickest benefit.
2. The stomata respond to both light and temperature.  They open when light strikes the leaf in the morning, and close at the end of the day.  They will also close when temperatures go above 85 degrees.  
3. Nutrients can move from the leaf surface to the interior of the plant in as little as one hour. Most sprayed materials are absorbed into, and move throughout the plant in a day’s time.  Hydroponic growers who feed using foliar sprays recommend spraying at least every 3 days. 
4. Most growers believe that foliar feeding, if used at all, is to enhance, rather than replace root-based feeding.
5. Do your foliar feeding when temperatures are below 85°F. The preferred spraying time is in the early morning, when stomata are open, and with ample time for nutrient absorption before temperatures go above 85 degrees.
6. If possible, avoid foliar feeding when the weather is very dry.  Absorption is said to be best with humidity of 50-60%.
7. The ideal pH for your spraying material is around 6.5.  
8. For foliar feeding, use a much more dilute solution than for root feeding. One sixth of the amount used for root feeding is a good place to start. 
9. Micronizing, or even nano-sizing the fertilizer particles will further reduce the amount needed and improve the plants’ absorption and use of the nutrients. 
10. Use a sprayer that creates the finest mist possible. This will produce a more even spread of the solution on the leaf.
11. Using a surfactant or wetting agent to prevent beading (1/4 tsp. per gallon of spray), such as a mild liquid soap that will not damage the cuticle layer of the plant’s leaves, allows more of the spray to remain on the leaves, and may increase the fertilizer’s effectiveness by as much as 300%.
12. If possible use water with no minerals or chlorine to avoid clogging sprayer or damaging sensitive plant leaves.
13. Spray when there is little or no wind, and avoid watering for 24 hours if possible.