Safe to Use Fertilizer on Herbs?
Answered by: Conrad Richter
Question from: Patti
Posted on: July 22, 2005

I have a serious question. My sister and I have had many debates over Miracle-Gro for herbs. I don’t think it’s safe to spray it on herbs, flowers yes, but herbs? What do you think, is it safe. My sister grows flowers, and I grow herbs as organic as possible.

Miracle-Gro fertilizers come in a wide range of formulations: liquid and granular, slow release and fast feed, etc. I suspect what you mean to ask is whether it safe to use chemical fertilizer on herbs, be it Miracle-Gro or any other similar brand of fertilizer.

"Safe" can mean two things. Is the fertilizer safe for the plants? Or are herbs grown with the fertilizer safe for human consumption?

It is partly true that it’s better to grow herbs without fertilizer because then the essential oils in the leaves will be more concentrated and the leaves will have more flavour. But too little fertilizer could leave the plants stunted and the harvest small. When grown in the garden herbs do not require much feeding because there is plenty of room for the roots to spread. But herbs in containers such as pots, window boxes and planters are a different story: container-grown herbs have less room to grow and will exhaust the nutrients in the soil much more quickly. For container herbs we recommend supplementary feeding with any liquid fertilizer such as fish emulsion or cheically-based liquid fertilizers such as Miracle-Gro. Be sure to follow the label directions because too much fertilizer will "burn" the leaves and roots.

Fertilizers -- even the chemically-based ones -- are safe to use on herbs. The biggest concern is a possible buildup of salts on the foliage when harvested and used. Nitrates, especially, can affect health if one ingests too much; but nitrate residues on herbs are unlikely to reach levels hazardous to human health. Long before salt levels on plants become excessive for human health, plants will writher and die.

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