GRASS FAMILY-Gramineae
JOHNSONGRASS- Sorghum halepense (L.) Pers.
Johnsongrass is usually considered by many stockmen to be a good feed for their animals. It is a "good" feed source as long as the leaves do not produce a cyanide type of poison known as hydrocyanic (prussic) acid and then the grass becomes extremely deadly for all livestock.
What causes Johnsongrass to become poisonous? It appears that anything which influences normal plant growth may trigger the release of HCN within the plant: rapid leaf growth, or wilting caused by trauma in the form of trampling, freezing, dryness, or even the cutting of the plant.
How do you know when a plant has been traumatized and may be producing HCN? One doesn't know and stock are apt to be poisoned by Johnsongrass at any time. Acute poisoning results in death from respiratory failure following the first appearance of symptoms within a few hours; rapid and complete recovery may occur after a sub-lethal dosage (even after severe poisoning). Breathing is, at first, deep, becoming rapid and labored, finally resulting in noisy, violent gasping, then trembling, staggering, and convulsions; bloat is common in the late stages of poisoning.
This grass is a prohibited, noxious weed in Arizona and total eradication is almost impossible, due to its lengthy underground stems, rhizomes (up to 2 1/2 feet deep), and dormant seeds. An attractive leafy perennial, its height may reach between three to seven feet in height, and its blades may be two feet long and 1/4 to 3/4 inches in Iength. The plant's flowering tops may be as much as two feet long and produce dark, reddish-brown grains. It flowers from April to November and prefers to grow in irrigation ditches and in cultivated fields. It is found in elevations up to 6,000 feet.
[Poaceae. The grass family is undoubtedly the most important plant family in terms of usefulness to humans. All the world's important grain crops are grasses; the bamboos (giant grasses) are useful in building and crafts. Many grasses are used in lawns or as ornamental annual or perennial plants. Some botanists use Gramineae as the family name for grasses.] Sunset Western Garden Book, 1995