Sorghum (Sorghum bicolor) is a major global cereal grain belonging to the grass family, Poaceae. It is known for its resilience, thriving in hot, dry environments where other cereals struggle. It generally presents as a robust, upright grass.
Overall Stature and Growth Habit
Sorghum plants look similar to maize (corn), presenting as a strong, upright grass that varies significantly in height. Stature ranges from short, sturdy types bred for grain harvest (3 to 4 feet tall) to towering varieties used for biomass or forage. The tallest types can easily reach heights of 15 feet and sometimes exceed 20 feet.
The plant’s life cycle is typically annual for cultivated varieties, though some cultivars can be perennial. A field of sorghum appears dense and uniform, characterized by a single, thick central stalk (culm) that may produce several secondary shoots called tillers. This growth habit, combined with a vigorous, fibrous root system, provides the stability and water-extraction capability needed to endure dry conditions.
Detailed Look at Stems and Leaves
The main stalk, or culm, is a defining feature, being solid throughout its length, unlike many grasses that have hollow stems. This solid structure contributes to the plant’s strength and rigidity. The stem is divided by distinct, swollen joints called nodes, from which the leaves emerge.
The exterior of the culm often has a powdery, waxy coating, giving the stem a slightly bluish-green hue, particularly in the upper sections. Sorghum leaves are broad and elongated, similar to corn leaves, and are attached alternately at the nodes. Each leaf features a prominent central midrib and a sheath that wraps tightly around the culm.
The number of leaves on the main stem ranges from about 7 to 24, depending on the variety and growing conditions. Fully developed leaves can reach lengths of over two feet and several inches in width. At the point where the leaf blade meets the sheath, a ligule is present, which helps channel water down the leaf and away from the stem.
The Distinctive Panicle and Grain
The most recognizable feature of the mature sorghum plant is its seed head, known as a panicle. The panicle is a branched cluster of flowers that eventually develops into the grain-bearing structure. Supported by the peduncle (the uppermost section of the stem), the panicle’s appearance is highly variable, ranging from dense and compact forms to loose, open, and drooping structures.
Flowering begins near the top of the panicle and progresses downward over several days. Within the panicle, individual flowers develop into the grain kernels. Sorghum grain is small, typically 2 to 4 millimeters in diameter, and round in shape.
The color of the mature grain is diverse, including shades of white, tan, red, bronze, and black. The color is often determined by a colored layer beneath the seed coat. A single panicle is prolific, capable of bearing between 800 and 3,000 kernels.
Visual Differences Among Sorghum Types
The overall look of sorghum changes significantly depending on its primary agricultural use, leading to distinct types. Grain sorghum, bred for easy harvesting, is typically the shortest type, often dwarfed to around 2 to 4 feet tall. This short stature is paired with compact panicles that hold the grain tightly.
Conversely, sweet sorghum and forage sorghum varieties are much taller, often reaching 8 to 15 feet, as they are bred for biomass rather than grain. Sweet sorghum is distinct because its stems are notably juicier and thicker than other types, due to high sugar content within the pith. Forage types are generally leafier than their grain counterparts, maximizing edible plant material for livestock feed.
Broomcorn is a specialized type of sorghum grown not for its grain or stalk juice but for the long, fibrous branches of its panicle. These branches are significantly longer and straighter than those of grain varieties, giving the plant a distinct, brush-like head used historically to make brooms. These visual variations allow the plant to be cultivated for a wide range of purposes, from food and feed to syrup and bioenergy.