Fall panicum, Panicum dichotomiflorum

Life Cycle

Annual

Propagation

Reproducing only by seed.

Stems

Stems are 1 to many 10 - 180 cm 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 (a).

Leaves

lower leaf blades and leaf sheaths of very young plants finely hairy (b), blades and leaf sheaths produced higher up the stem usually completely hairless; nodes (a) of stem enlarged and prominent; leaf sheath somewhat inflated (c) or loosely fitting around the stem just above each node; leaf sheaths split (B), their margins (d) very thin, membranous, white or colourless, and separate or overlapping each other; ligule (e) a fringe of hair 1.5 - 3 mm long; no auricles

Flowers and Fruit

Inflorescence of several much-branched panicles; terminal panicle (C) at the end of each stem large and bushy, 15 - 50 cm long and almost as wide, the branches thin but quite stiff; panicles on lower branches (f) small, compact, and often remaining partially enclosed (g) by the leaf sheath from which they emerge; spikelets (h) borne singly at the ends of the tiny branches, about 2.5 - 2.7 mm long by 1.0 - 1.1 mm wide, each containing a single floret ( “seed”) about 1.8 - 2.0 mm long by 0.9 - 1.0 mm wide, gray-brown with 5 parallel beige veins. Flowers from August to September.

Roots and Underground Structures

Fibrous root system.

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.

Competitiveness

Corn yield loss (%)*: 2 % at 1 plant/m2 10 % at 5 plant/m2 Soybean yield loss (%)*: 2 % at 1 plant/m2 10 % at 5 plant/m2 *assumes that the weed has emerged with the crop and has been left uncontrolled all season.

Distinguishing Features

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.

Toxicity

Fall panicum is not known to be toxic.

Human Health Issues

Fall panicum is not a known allergen.

Forage Quality

No information exists at this time.

Species Benefits

No information available at this time.

Power Ranking Corn

Power Ranking

↑ 12

 

Power Ranking Soybeans

Power Ranking

↑ 19

 

Biological Control

Currently none available for this weed. For the latest research on biological weed control: http://res2.agr.ca/Lethbridge/weedbio/index_e.htm#toc

Biopesticide Control

Currently none available for this weed.

Herbicide Resistance

No documented cases of herbicide resistance to date. For more information on weed resistance: http://www.plant.uoguelph.ca/resistant-weeds/


Figure #1.

Fall Panicum: A. Plant. B. Leaf-base. C. Panicle. D. 2 spikelets.


Figure #2.

Ligule: hairy.


Figure #3.

Leaf blade: young seedlings; lower leaf surface is densely hairy, but becomes less hairy with age. Older lseedlings, smooth and hairless with a very prominent mid-rib.


Figure #4.

Leaf sheath: margins are hairless.


Figure #5.

Seed head.


Figure #6.

Whole plant.