Johnson grass

Sorghum halepense

Description

Perennial grass, smooth, with many long, horizontal and branching rhizomes. Stems are upright, 120-160 cm high. Long (40-80 cm) and large (1-2 cm) leaves. Inflorescence in the shape of pyramidal panicles, very branching. Geminal or colourless spikelets: one of them is sessile with a hermaphrodite flower, the others are stalks with one male flower. Lemma is reefed or muticous. Spikelets are shed at maturity. Caryopsis are completely wrapped in lemma. Frequent allogamy. n=20-40.
Grains are wrapped in lemma. TKW= 8-12 g.

Native to the Mediterranean region (southern France, Spain, Portugal and North Africa), it was later implanted in some tropical and subtropical regions. It is grown in the south of the United States (Texas, Florida etc.)

Johnson grass requires a minimum knowledge and control of the plant before cultivating it. Its toxicity can be very dangerous for cattle (less for sheep, horses, etc.). The hydrocyanic acid present in the plant, in particular when it grows very little (either at the beginning of the growth, or when this growth was slowed down by the cold or drought), only disappears at a relatively advanced stage (when the plant is about 50 cm and at the beginning of panicle formation). Its usage in hay or in silage also reduces a toxicity.
Cultivates as well as a dry crop as irrigated, it provides one first cut, regrowth can be grazed immediately afterwards. The animals eat it without difficulty, in particular before the appearance of panicles which makes it much more woody. After that, it is still possible to use it for silage, but it will mainly be used for the formation of grains.

Climate: Johnson grass needs heat, absolutely not supporting frosts nor too cold winters. Accommodating as well to strong rains as to dry summers, it is advised to irrigate it if droughts persist.

Soil: Ideally, Johnson grass is implanted in a fertile soil, rich in humus and nutrients. Under optimal conditions, Johnson grass quickly becomes invasive.

In the first year, Johnson grass provides one cut and one to two regrowths. In subsequent years, the annual number of cuts can go up to four in irrigated crops. After that it will have a tendency to completely turn into lawn and the yield decreases. It should then be returned, which is facilitated by a close mowing, which it does not tolerate.
To harvest its grains, it is important not to wait for complete maturity, spikelets brake easily.