Foliar feeding is a method of plant fertilization which involves applying fertilizer directly to the leaves in the form of a solution which is sprayed on. The tiny pores in the leaves allow the fertilizer to pass into the plant, providing needed nutrition. One of the advantages to foliar feeding is that it can be very fast acting, which is useful when gardeners are struggling with droopy foliage and dim colors, but it needs to be done carefully to avoid damaging the plants.
Both natural and synthetic nutrients are available in solutions designed for foliar feeding. Typically, the fertilizer needs to be diluted in water before application, to avoid burning the leaves, and it should be applied in the morning or evening, when the pores of the leaves are most likely to be open. The pores will be closed during the heat of the day to prevent water loss, and they will also tend to be closed during extremely cold weather.
This fertilizing practice can be used on indoor and outdoor plants, along with crops which are being grown hydroponically. In all cases, foliar feeding is not designed to work on its own. The plant still needs to be able to absorb nutrients through its roots, which means that the soil needs to be in good condition, and the soil should be tested regularly to confirm the presence of necessary nutrition. Foliar feeding can be utilized to supply missing trace nutrients without overwhelming the plant, and to encourage healthy, rapid cell growth in plants which appear to be struggling.
Gardening supply stores carry foliar feeding solutions, and their staff may have specific recommendations for customers. It's important to test the soil to see which nutrients the plant is getting, and to know about the specific nutritional needs of a particular plant to confirm that the right nutrients are supplied in a foliar feeding session. Gardeners should also be aware that because this technique causes the leaves to get wet, it can promote the growth of harmful fungi, and cause burns from sun exposure.
When foliar feeding is utilized on food crops, it is important to wash the food before eating. Synthetic fertilizers can be harmful to ingest, while natural products can carry traces of fungi and pathogens which may cause harm to people. While natural products are usually treated to reduce this risk, it's impossible to catch everything, and it is better to be safe than sorry.
