Those with culinary experience recognize the bay leaf as a dried spice that is used to flavor foods and then removed prior to serving. Few may know the bay tree (Laurus nobilis), a Mediterranean native evergreen tree that produces these leaves, maturing 30 to 40 feet tall. Slow-growing and well-suited for container culture, the bay tree survives outdoors year-round in U.S. Department of Agriculture Hardiness Zones 8 through 11 where winters are not severe.
Fresh living bay leaves are tapering ovals that botanically are described as oblong-lanceolate, according to the South China Botanical Garden Herbarium. The leaf margins (edges) are smooth or undulate, which means slightly wavy. The tip or apex of the leaf is pointed.
On both the upper and lower leaf sides, the midvein is slightly raised. Thin, lateral veins, ten to 12 pairs, branch off from the midrib and expand outward to the leaf's edge. As the veins reach the leaf edge, they branch into forks, interconnect with each other and diminish.
Bay leaf ranges in mature size from 2 to 3-1/2 inches long and 3/4 to 1-1/2 inches wide according to the South China Botanical Garden Herbarium. Young leaves are smaller and located at branch tips, while the largest leaves persist across all branches that receive ample sunlight.
Newly emerging leaves are highly glossy and pale green, sometimes with a hint of yellow or pink. Growth begins in the warmth of spring, although branch tip growth occurs across summer and fall with a less vigorous or surreptitious emergence of a few new leaves. By the end of fall, the youngest leaves attain their deepest green color and will become darker green across the cooler winter months.
Leaves contain essential oils (hydrocarbons) limonene, camphene, and sabinene. According to the South China Botanical Garden Herbarium, the oil constitutes no more than one half percent of volume of the leaf blade. Botanical Online lists several components of the bay leaf. Acetic, formic, pelargonic and propionic acids exist as does the alcohol eugenol. Dried leaves are less potent as the water and alcohol molecules are gone.
Botanical Online states that fresh bay leaf contains water, lipid and carbohydrates. The nutrients calcium, potassium, magnesium and phosphorus are present. Leaves also contain folic acid, vitamins C and B6, and niacin.