Foliar is defined as ..... Of or relating to a leaf or leaves.

The cuticular and the stomatal level of the leaf structure affects foliar fertilization.

Foliar fertilizers are fertilizers that are applied to boost nutrient density in crops and to correct nutrient deficiencies.

something applied to the leaves

CAN I FOLIAR FEED WITH GH NUTRIENTS? Answer: Of course. Make sure you use a weaker nutrient solution than you would for root feeding. Avoid foliar feeding in the heat of the day and under excessive sunlight. Generally, the best times to foliar feed are in the early morning and late afternoon. Make sure you spray the undersides of the leaves. This is where the stomata or "lungs of the plant" are located, and where maximum absorption occurs. This answer was collected from: http://www.generalhydroponics.com/genhydro_US/faqnute.html