Ontario Weeds: Giant foxtail

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Name
  2. Other Names
  3. Family
  4. General Description
  5. Stems and Roots
  6. Flowers and Fruit
  7. Habitat
  8. Similar Species
  9. Related Links

Name: Giant foxtail, Setaria faberii Herrm.,

Other Names: sétaire géante, sétaire de Faber

Family: Grass Family (Gramineae)

General Description: Annual, reproducing only by seed. Similar to Green foxtail, but generally larger.

Photos and Pictures

Giant foxtail

Giant foxtail

Giant foxtail (A - upper part of plant; B - comparison of giant foxtail head, left, with green foxtail head, right).

Giant foxtail (A - upper part of plant; B - comparison of giant foxtail head, left, with green foxtail head, right).

Giant foxtail. G. Young plant showing finely hairy leaf surfaces. H. Leaf-base showing dense covering of very short hairs on upper surface of leaf-base, hairy ligule with longer hairs at margins of collar, and short hairs along edge of leaf sheath.

Giant foxtail. G. Young plant showing finely hairy leaf surfaces. H. Leaf-base showing dense covering of very short hairs on upper surface of leaf-base, hairy ligule with longer hairs at margins of collar, and short hairs along edge of leaf sheath.

Stem and leaf-base characteristics of a typical grass.

Stem and leaf-base characteristics of a typical grass.

Stems & Roots: Stems up to 2m (6.5ft) high, smooth; leaf sheaths mostly smooth, except hairy along the margins; leaf blades 30-55cm (12-21.5in.) long, 3-17mm ( 1/8-2/3in.) wide, usually finely hairy throughout the entire upper surface of all leaves and occasionally also on the undersurface (seen by rolling the leaf over a finger and viewing it against the light); ligule a dense band of hairs, about 1.0mm (1/25in.) long; no auricles;

Flowers & Fruit: Inflorescence dense, spike-like, erect or the larger ones usually somewhat curved or nodding, 4.5-17cm (1-4/5-6-7/10in.) long and 1.5-3cm (3/5 - 1-1/5in.) thick, surrounded by light yellowish-green awn-like bristles which give the inflorescence a bottle-brush appearance; spikelets 1.5-3mm (1/16-1/8in.) long; grains ("seeds") light green and abundantly cross-wrinkled. Flowers from late July to October.

Habitat: Giant foxtail is native to China and was recently introduced from the USA where it is a very common weed; it is becoming abundant in fields and waste places in southern and eastern Ontario.

Similar Species: It is distinguished from Green foxtail by its usually larger, nodding inflorescence, its distinctly cross-wrinkled grains and usually hairy upper surface of leaves, and from Yellow foxtail by its larger, greenish-yellow rather than orange-yellow inflorescence, and by the upper surfaces of its leaf blades being finely short-hairy throughout their length rather than bearing a few long, kinky hairs near the stem. The technical character that distinguishes Giant foxtail from Green foxtail is that its second or upper glume covers only about ¾ of the fertile floret, whereas in Green foxtail it covers nearly the entire floret.

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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For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 01 June 2002
Last Reviewed: 01 November 2003