This is especially true if the plant is lacking iron, which is often indicated by yellow leaves with green veins. A foliar feeding is especially good during periods of rapid growth. Choose an overcast day to fertilize foliage. Some tender leaves can burn if you apply nitrogen in the full sun. Mix the fertilizer in a garden sprayer.
Seaweed fertilizers are especially effective when applied directly to foliage.
Spray the plant with the fertilizer solution, making sure to cover both sides of the leaves. Clean the sprayer with fresh water after you are finished. The salts from some fertilizers will cause the metal parts to corrode. Always mix and apply fertilizer according to label directions. Inc. How things get done.