Sorghum is a major global cereal crop and a large annual grass species (Sorghum bicolor). Its appearance varies greatly depending on whether it is grown for grain, forage, or sweet syrup production. The plant is structurally similar to corn, but its morphology has been adapted by breeders for different agricultural purposes, meaning a single description cannot capture the look of all types.
Overall Structure and Stems
The basic physical structure of a sorghum plant is defined by its culm, the main stalk, giving it a resemblance to corn or sugarcane. Plant height is highly variable, ranging from dwarf grain varieties that stand about three feet tall to biomass and sweet types that can exceed 15 feet.
The stalk is robust and cane-like, divided into distinct segments by prominent nodes where the leaves attach. Unlike some other grasses, the interior of the sorghum culm is typically solid in both the nodal and internodal regions, though the core may sometimes be spongy. Sorghum often develops a noticeable powdery, waxy coating, known as a “bloom,” particularly on the upper leaf sheaths, which can give the stalk a bluish-white appearance.
Leaves and Foliage
Sorghum leaves are organized in an alternating pattern along the stalk, featuring a sheath that wraps around the stem and a flat, elongated blade. These leaves are broad, parallel-veined, and range from pale green to bluish-green, depending on the variety and the waxy bloom. The small leaf surface area is an adaptation that helps the plant conserve water in hot, dry environments, sometimes causing leaves to fold closed under drought stress.
The leaves have a prominent midrib running down the center, which often appears greenish-white and noticeably widened toward the base of the blade. At the junction where the leaf blade meets the sheath, there is a structure called the collar, and a membranous or hairy flap known as the ligule is usually present. Most sorghum varieties lack the ear-like appendages, or auricles, that are found in some other grasses.
The Panicle (Seed Head)
The most visually distinct part of the plant is the panicle, which is the terminal, elaborately branched structure that produces the seeds, or grain. This seed head is supported by the peduncle, the section of the stem immediately below the panicle. Sorghum panicles exhibit extensive morphological diversity, ranging from compact, tight, and dense clusters to loose, open, and even broom-like shapes.
Each panicle is composed of numerous spikelets, the floral units that produce the grain, and the entire head can contain hundreds to thousands of seeds. The seeds are relatively small, typically about four millimeters in diameter. Sorghum grain colors are diverse, including white, yellow, red, bronze, tan, and dark brown or black varieties.
The overall color of the mature panicle is influenced by the color of the glumes, the outer, protective scales covering the seed. These glumes can be black, red, brown, or tan, and they typically partially cover the developing grain. Breeders often select for large, well-exserted heads that extend cleanly out of the flag leaf sheath.
Visual Differences Among Major Sorghum Types
The three major commercial types of sorghum—grain, sweet, and forage—are differentiated by their overall architecture and the specific features of their stems and heads. Grain sorghum is typically the shortest type, bred for a compact, erect growth habit and a high ratio of seed-to-stalk mass. Its panicle is the focus, often appearing round or tight-headed to maximize grain production.
Sweet sorghum plants are notably taller and distinct due to their thick, juicy culms, which are bred to accumulate high sugar content. While they produce a panicle, the primary visual feature is the large, cane-like stalk, which appears robust and thick compared to other types. The focus is on stem biomass rather than the seed head.
Forage sorghum and its close relative, Sudan grass, are grown to be tall and leafy, often reaching heights between 7 and 15 feet. These types are valued for their high vegetative biomass and have finer stems than sweet sorghum, with a greater overall leaf mass. Forage types are known for prolific tillering, producing multiple side shoots from the base, which gives the stand a denser, bushier appearance.