The plant commonly known as tobacco belongs to the genus Nicotiana, which is part of the nightshade family, Solanaceae. This family also includes potatoes, tomatoes, and peppers. While the genus contains many species, the one overwhelmingly cultivated for commercial use is Nicotiana tabacum. This cultivated tobacco is native to the tropical and subtropical Americas but is now grown worldwide for its commercially valuable leaves.
Overall Size and Growth Habit
Nicotiana tabacum is a robust, herbaceous plant that is typically grown as an annual crop, completing its life cycle in a single season. In warmer, frost-free climates, however, the plant can technically function as a tender perennial. The plant develops a thick, stout central stalk that is not heavily branched.
This main stem is often covered in fine, sticky hairs, which give the entire plant a slightly viscid or hairy texture. A mature, unharvested tobacco plant can reach an overall height between 3 and 6 feet. The plant’s architecture, with its large leaves radiating from the central axis, often forms a broad, pyramidal or conical shape.
Identifying the Leaves
The leaves are the plant’s most defining and commercially significant feature, being notably large and coarse. They grow in an alternate pattern up the stalk, increasing in size toward the middle of the plant. The leaf blades can grow to be over 20 inches (50 cm) long and have an ovate, elliptical, or obovate shape.
The upper leaves are often sessile or sub-sessile, appearing to clasp the stem. Their color ranges from a pale to deep bluish-green, depending on the variety and nutrient content of the soil. The texture is a primary identifying characteristic, as the leaf surfaces are covered in numerous trichomes, which are small, fine hairs.
These trichomes are often glandular, producing a sticky, resinous exudate that makes the leaves feel velvety or sticky to the touch. This sticky surface serves as a natural defense mechanism against certain insects. The leaf margins are typically smooth, without teeth or lobes.
Flowers and Reproductive Structures
If left to mature, the tobacco plant develops an inflorescence, or flowering stalk, at the apex of the main stem. The flowers themselves are organized into multi-branched clusters called panicles. Each individual flower is trumpet or funnel-shaped, with the petals fused into a tube.
The corolla, or collection of petals, typically opens into five lobes at the tip and displays colors ranging from white and cream to pink or reddish hues. After pollination, the flower transitions into a fruit structure, which is a small, capsule-like seed pod. This capsule is narrowly elliptical or egg-shaped and contains a vast number of minute, spherical seeds. The fruit is dry and splits open when ripe to release the tiny seeds.