What Fertilizers Are Used for Herbs?

With most herbs, less fertilizer means better taste.

Herbs, just like any other garden plant, have different needs in terms of water, drainage, sunlight and nutrients. General wisdom says when it comes to fertilizing herbs, err on the side of too little rather than too much. There are, however, certain situations in which herbs benefit from the addition of nutrients through the application of fertilizers or soil amendments.

Fertilizers

The role of fertilizers is to provide nutrients that plants may not get from the soil. They are applied at the base of the herb plant or directly on leaves. Nitrogen (N) promotes leaf growth and color. Phosphorus (P) helps develop roots and seeds. Potassium (K) improves plant health, creates resistance to disease and stress, and improves flavor and color. Water-soluble fertilizers are absorbed quickly, while slow-release fertilizers provide nutrients over a long period of time. They are available as stakes or tablets that are placed in the soil near the roots.

Soil Amendments

Soil amendments are various forms of organic matter, such as composted yard waste, that are mixed into the soil. Amendments can improve the nutrient content of the soil, increase the activity of beneficial microorganisms, and enhance soil structure. Organic matter can also alter the pH of the soil. Horticulturists recommend that you feed the soil first (through amendments), and then feed the plants (via fertilizers) only if needed. This is especially good advice for growing herbs.

Herbs in the Garden

Most herbs, especially the Mediterranean species such as basil, lavender, oregano, rosemary and thyme, prefer sandy soil that is relatively low in nutrient content. An excess of fertilizer or organic matter can lead to root and stem rot and will lower the essential oil content that gives herbs their scent and flavor. There are exceptions to the rule, however. When planting herbs that will be harvested frequently, such as basil, chives and parsley, prepare the soil by working in compost or well-rotted manure. Commercial low-release fertilizer tablets may be useful in the beginning stages of growth, but no additional fertilizer applications should be needed. Herbs are more often damaged by overfertilizing than by underfertilizing.

Herbs in Containers

Container herbs need to be watered more frequently than those planted directly in the garden, a practice that leaches nutrients from the soil. If the nutrient level drops too far, annual herbs will set seeds and lose their leaves. To avoid that problem, fertilize container herbs regularly. Liquid fertilizers such as seaweed or fish emulsion will benefit most container-grown herbs. Slow-release tablets can be used, but watch for fertilizer salt buildup as it can burn the roots. Herbs in pots that sit outside during the heat of summer should be fertilized every two weeks, while indoor herbs can rest for a month between applications.

References

• University of Georgia College of Agriculture & Environmental Sciences; Herbs in Southern Gardens; Wayne J. McLaurin, et al.; January 2011
• Maryland Cooperative Extension; Soil Amendments and Fertilizers; Jon Traunfeld, et al.; April 2003
• Alabama Cooperative Extension Service; Growing Herbs; Kerry Smith, et al.; August 2010
• Alabama Cooperative Extension Service; Growing Herbs in Containers; Kerry P. Smith, et al.; July 2003
• University of Missouri Extension; Growing Herbs Indoors; Kathryn Keeley, MS

Resources

• University of Illinois Extension; Growing Herbs in the Home Garden; James C. Schmidt
• Penn State Department of Agriculture; Growing Herbs Indoors; Kathleen M. Kelley; September 2002