All Rosemarys are Not Created Equal

Q. I use rosemary which I purchase from the store for cooking.  It is expensive and does stay fragrant very long if I don't use it all. I would like to plant rosemary in our yard so that I can use it in my cooking.  Is there a difference between rosemary used for "cooking" and rosemary used in landscaping?

A. There are several varieties of rosemary but most are selected for landscaping rather than cooking. Many of the landscape varieties have horizontal or prostrate growth. However, these landscape varieties can be used for cooking as well. But varieties selected for cooking are usually upright and often have a higher oil content. Upright growth is easier to harvest.

Rosemary comes in both upright forms and prostrate. Upright forms are easier to harvest.

Growing rosemary as an herb is different from growing rosemary as a landscape plant. Two traits are considered desirable in rosemary as an herb; upright succulent leaf and stem growth and a high oil content.

To grow rosemary for cooking, push new growth with nitrogen fertilizers and harvest before flowers are produced. Seldom is rosemary left to flower when used as an herb but the new growth is dried or used fresh. Flowers may be attached when sold at Farmers Markets.

Rosemary flowers contain the most and better oil. Commercial producers focus on leaf and stems for oil production because it is easier to produce even though the oil is not high quality.

The best oil comes from rosemary flowers. However, most commercial oil production is from leaves and stems which produces more abundant oil but it is inferior to the oil produced in the flowers. The same technique is used except high phosphorus fertilizer is applied to improve oil production and harvesting is done when flowers are present for higher-quality oil.

Some of the better varieties for cooking include Benenden Blue, Flora Rosa, Tuscan Blue, Majorca Pink, Arp, Albiflorus, Huntington Carpet, McConnell's Blue, Irene, Holly Hyde and Hill Hardy to name a few.