Foliar feeding

Can I foliar feed plants using hydroponic nutrient solution?
Stoner Steva,
British Columbia

Yes. Plants absorb water and nutrients through openings on the leaves called stomata. These pore-like openings also permit CO2 to enter and release oxygen.

Foliar feeding is a very efficient way of providing plants with nutrients because it goes directly to the plant canopy and doesn’t have to take the long trip from medium to roots and up the stem.

Make sure the solution you are using is not too concentrated by spraying a few healthy leaves to see if there is any damage. If the leaves curl or look unhealthy in any way two days after spraying, dilute the mix by 50% and try again. Always foliar feed early in the light cycle so the plant parts have a chance to dry off.

Foliar feeding too often can cause over-fertilization. Weekly sprays are generally the maximum. After foliar feeding the first day, spray the plants with pH adjusted water daily for a few days. This provides the plant an opportunity to absorb any fertilizer residue.

When plants are regularly foliar fed, they use less nutrient absorbed by the roots, so the concentration of the nutrient solution can be lowered a bit.

Foliar feeding can also be used to correct deficiencies quickly. For instance, spraying a solution of a teaspoon of magnesium sulfate in a quart of water until it drips off the plant can treat a plant that is suffering from a magnesium deficiency. This provides the plant with magnesium very quickly. Magnesium sulfate should be added to the medium or hydroponic solution as well, so new growth has access to the mineral.

Foliar feeding is especially useful in delivering nutrients that don’t translocate, that is, move from one part of the plant to another. Phosphorous and iron are two examples of this.

Stop foliar feeding buds at least three weeks before harvest so no fertilizer residue remains when the bud is picked.

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