Brown top millet (\(Urochloa\ ramosa\)) is an annual warm-season grass cultivated globally for both its grain and its use as forage. This grain plant is a member of the Poaceae family, valued for its rapid maturation and adaptability to various soil conditions. To accurately identify brown top millet, one must examine the individual seed, the vegetative growth, and the distinct appearance of its mature seed head.
Appearance of the Grain
The individual grain of brown top millet, once threshed, is a small, minor millet seed. Its shape is ellipsoid or oval, which is typical for many grains in this category. The physical dimensions are minute, with the average length measuring about 3.00 millimeters, a width of 1.79 millimeters, and a thickness of 1.15 millimeters.
When fully mature, the seed exhibits a light tan or yellowish-brown color. The 1000-seed weight is low, averaging around 3.42 grams.
Vegetative Characteristics
The stems can grow either erect or prostrate along the ground. When growing upright, brown top millet typically reaches a height of 1 to 3.5 feet (30 to 105 centimeters) at maturity. The smooth stems feature nodes that are minutely hairy or pubescent.
The leaves are long, narrow, and lance-shaped, generally hairless across the blade surface. Leaf blades can range in length from about three-quarters of an inch up to 10 inches long and are typically between 1/8 and 1/2 inch wide. A small ligule, a fringe of fine hairs, is present where the leaf blade meets the stem.
The Defining Seed Head (Inflorescence)
The inflorescence, or seed head, is the source of the plant’s common name and its most defining visual feature. It is an open panicle structure where the flowers are loosely arranged along a central axis. The panicle consists of between 3 and 15 individual branches, which can range from one-third of an inch to 3 inches in length.
The change in coloration gives the plant its “brown top” designation as the seeds reach full maturity. Initially, the developing flowers are white. As the grain ripens, the entire panicle dries and transitions to a characteristic dark brown or purplish-brown color. This color contrast with the still-green foliage below is the clearest visual identifier when the plant is viewed in the field.