Ontario Weeds: Giant foxtail
Table of Contents
- Other Names
- General Description
- Stems and Roots
- Flowers and Fruit
- Similar Species
- Related Links
Name: Giant foxtail, Setaria faberii
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.
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.
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.
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