Ontario Weeds: Fall panicum

Table of Contents

1. Name
2. Other Names
3. Family
4. General Description
   • Photos and Pictures
5. Stems and Roots
6. Flowers and Fruit
7. Habitat
8. Related Links

Name: Fall panicum, Panicum dichotomiflorum (L.) Michx. var. geniculatum (Wood.) Fern.

Other Names: PANDI, panic d'automne géniculé, Smooth panicum, Smooth witch grass, Spreading panic grass, Wire grass

Family: Grass Family (Gramineae)

General Description: Annual, reproducing only by seed. It is distinguished from Witch grass by its coarser panicle, the zigzag appearance of its longer stems, and the absence of hair on the leaf sheaths and leaf blades in the upper part of the plant; and from Proso millet by its hairless upper leaf sheaths and blades and its smaller spikelets and "seeds" that are only gray-brown in colour.

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Photos and Pictures

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Stems & Roots: Stems 1 to many from a coarse fibrous root system, 10-180 cm (4 in.-6 ft) long, erect or spreading or lying nearly prostrate on the ground; often rooting from nodes in contact with the soil, usually bending in a zigzag manner at each node or joint; lower leaf blades and leaf sheaths of very young plants finely hairy, blades and leaf sheaths produced higher up the stem usually completely hairless; nodes of stem enlarged and prominent; leaf sheath somewhat inflated or loosely fitting around the stem just above each node; leaf sheaths split, their margins very thin, membranous, white or colourless, and separate or overlapping each other; ligule a fringe of hair 1.5-3 mm (1/16-1/8 in.) long; no auricles; inflorescence of several much-branched panicles; terminal panicle at the end of each stem large and bushy, 15-50 cm (6-20 in.) long and almost as wide, the branches thin but quite stiff; panicles on lower branches small, compact, and often remaining partially enclosed by the leaf sheath from which they emerge.

Flowers & Fruit: Spikelets borne singly at the ends of the tiny branches, about 2.5-2.7 mm (1/10 in.) long by 1.0-1.1 mm (1/25 in.) wide, each containing a single floret ( "seed") about 1.8-2.0 mm (1/14-1/12 in.) long by 0.9-1.0 mm (1/25 in.) wide, gray-brown with 5 parallel beige veins. Flowers from August to September.

Habitat: Fall panicum is a native plant in eastern North America but has become a weed of significance in cultivated land only since about 1968. It now infests many thousands of acres of prime corn land in the 6 southwestern counties of Ontario and is present in many more farms in all the counties south and west of a line from Hamilton to Grand Bend. Outside this region it is known to occur only occasionally in cultivated land in central Ontario, in streamside locations along Bear Creek southeast of Ottawa, and in several waste areas in Ottawa city and along the St. Lawrence River.

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Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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