The tobacco plant belongs to the genus Nicotiana, a member of the Solanaceae family, commonly known as the nightshades. This family includes species like tomatoes, potatoes, and peppers. Nicotiana tabacum, or cultivated tobacco, is the most recognized species, grown primarily for its foliage. This guide details the physical characteristics of the tobacco plant for identification.
General Architecture and Stem
Cultivated tobacco is an herbaceous plant typically grown as an annual, completing its life cycle within a single growing season. It develops a robust, erect central stem that often reaches heights ranging from 3 to 10 feet in mature specimens. This thick stalk generally remains unbranched until the upper portion where the inflorescence develops.
The entire stem and leaves are covered in fine, sticky hairs, known as viscid-pubescence. This coating gives the plant a tacky or clammy feel upon touch. The overall silhouette is columnar, with large leaves spiraling up the central axis, resulting in a dense, leafy appearance.
Distinctive Features of the Leaves
The leaves are the most characteristic feature of the tobacco plant, arranged alternately along the stem. They are notably large, with mature leaves often exceeding 20 inches (50 centimeters) in length. Their size and density are primary identifiers for the plant.
Leaf shape is typically ovate, elliptical, or lance-shaped, featuring an entire (smooth) margin. The leaves attach to the main stem in a unique manner, often appearing sessile, meaning they lack a petiole (leaf stalk). The base of the leaf blade often extends down and partially clasps the stem, a characteristic called decurrent attachment.
The color of the leaves ranges from medium to pale green or yellowish-green, varying by variety and growing conditions. Their texture is soft and somewhat velvety due to the dense covering of minute glandular hairs (trichomes). These hairs contribute to the sticky feel and give the leaves a downy or fuzzy look.
Flowers and Seed Capsules
As the plant matures, a terminal cluster of flowers, known as a panicle, emerges at the top of the main stalk. The individual flowers are recognizable by their trumpet or tubular shape. The corolla (fused petals) is long and slender, expanding into a five-lobed limb at the tip.
The flowers of Nicotiana tabacum are typically pink, rose, or reddish-pink, though white or greenish-white variations occur. They are often fragrant, especially in the evening, attracting pollinators. Following fertilization, the flower develops into a small capsule. This capsule measures between 0.5 and 0.8 inches long and contains a large number of minute, angular seeds.
Notable Species Differences
While Nicotiana tabacum is the most commercially grown, other species, such as Nicotiana rustica, display distinct visual variations.
Nicotiana tabacum
N. tabacum typically grows taller, reaching 6 to 10 feet. It is characterized by large, sessile, or stem-clasping leaves. Its flowers are long and slender, usually presenting in shades of pink or reddish-pink.
Nicotiana rustica
N. rustica, often called Aztec tobacco, is a shorter, more robust plant. Its leaves tend to be more rounded or ovate compared to the elongated leaves of N. tabacum. Crucially, N. rustica leaves have a distinct petiole (leaf stalk) and do not grow down the stem. The flowers are often greenish-yellow and are noticeably shorter than those of the cultivated species.