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Johnson Grass

Sorghum halepense

photo of johnson grass © by Michael Plagens

Observed in Aug 2009, Gilbert, Maricopa Co., Arizona, USA.

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PERENNIAL or ANNUAL: Robust annual achieving a height in excess of 2 meters under favorable conditions. Frequently produces thickets as abundant rhizomes grow laterally giving rise vegetatively to many additional plants. Vigorous growth occurs during hot months when C4 photosynthesis gives a tremendous boost.

INFLORESCENCE: Broad, open panicle with reddish tinged spikelets. Blooming June through October.

LEAVES: Blades are about 2 to 5 cm wide and 100+ cm long. The liguleconsists of long hairs.

RANGE: In the Sonoran Desert this grass is found mostly in disturbed habitats with plenty of moisture. Terraces and flood zones in riparian habitat. Ditches and margins of irrigated field. Found across North America. It is native to Eurasia and its aggressive growth characteristics have garnered it weed status in most districts. It likely displaces native species in Sonoran riparian habitats.

FRUIT: Grains are elyptic and relatively large. Intermediate hybrids with cultivated sorghum produce larger, heavier grains.


Poaceae -- Grass Family

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Copyright Michael J. Plagens, 1999-2009