Foliar application of fertilizer, insecticide, and fungicide is common practice in both indoor and outdoor marijuana gardens. Fertilizer products are absorbed through the leaf stoma and enter the plant’s system directly. Most pesticides and anti-fungal products are intended simply to coat the plant surface. Some products contain both a contact killer and a systemic component that will continue to treat and protect your plants from the inside.
Foliar products are commonly applied via pump sprayer or better yet through an Hudson Atomizer. Atomizers use electric motors to create a powerful jet of fine mist suitable for applying large volumes of foliar product. Atomizers work great for outdoor foliar jobs, but may also be used indoors with proper precautions. I love atomizers. They make large spray jobs small.
My favorite method of applying foliar products is dipping. Dipping is best suited for small plants and clones, like those shown in the video, and works best before you pot your plants in soil. You may still be able to dip Marijuana plants after transplanting them into soil; but you risk contaminating your dipping solution with soil or medium. You can mitigate this by using a stiff cardboard disk to cover the soil or medium. Simply punch a hole in the center of the disk a little larger than the diameter of the base of the stem, and cut a slit from the center hole to the outside edge to slide the stalk through.
Proper dipping assures complete product coverage; but surface tension can prevent water from thoroughly wetting the leaves and stems. To reduce surface tension, add a surfactant to your foliar dip. There are several surfactants available. Some contain mysterious chemicals, while others are naturally derived from yucca tree extract. My favorite surfactant is Dawn brand dish detergent. I use the original formula, not the antibacterial or scented versions. In fact, I am so fond of Dawn I often use it in my fertilizer reservoir solutions as well, at the rate of 1 tsp/50 gallons.