A very effective, gentle method for feeding many plants is by spraying the leaves with heavily diluted minerals.
Seaweed concentrate is particularly good. Seaweed concentrate is often mistakenly referred to as a fertiliser when it is really a soil conditioner.
However, when applied to foliage of plants on a monthly basis, the response can be so significant that the term "foliar feed" is accurate.
Some plants prefer this style of feeding better than others.
Citrus trees thrive with regular seaweed sprays, as do plants such as camellias, rhododendrons, azaleas, hydrangeas and roses.
Can also be used on leafy vegetables such as broccoli, cabbage, cauliflower and silverbeet.
The rate of uptake varies from plant to plant depending on many factors from the age to the thickness of the leaf. Older thicker leaves will have less uptake than newer leaf.
Foliar feeding should never be used as a sole or primary source of plant nutrition, but rather, a good support or supplementary programme to correct deficiencies of carefully selected nutrients, as an added bonus to boost your regular feeding proramme, thereby allowing your plant to get some of the "trace" elements that is hard to come by with normal / regular fertilising.
Whatever runs off the leaf will be absorbed by the root system. The most effective time of day to do foliar feeding is in the mornings as early as possible.
By doing this, it will allow the plant to absorb the solution fully - also if the day is a little overcast it will work in the plant's advantage.
The main thing to remember is to make sure it is well diluted and never exceed or use at a greater strength than suggested as other than wasting product it can sometimes damage sensitive plants. If ever in doubt apply a weaker mixture.