Timothy is widespread and naturalized in North America, having been introduced from Eurasia as a forage grass. Timothy occurs throughout Iowa in fields, ditches, and open areas. According to the Alien Plant Working Group, timothy is reported as being invasive in some states although it does not seem to present a problem in Iowa. Although timothy is a cool-season grass, its densely cylindrical flowering heads can be seen waving in the breeze from June into August. A closer look at the flowering heads reveals the strongly flattened spikelets with their characteristic U-shaped outline and translucent bristles extending from the edges. The glumes extend into stout awns that resemble horns. The other characteristic feature of timothy can be seen at the base of the stems, where frequently one or more of the internodes around ground level are swollen and bulblike. When grains are mature they tend to fall out of the spikelets with their attached chaff (lemma and palea) but as the flowering heads weather, spikelets will start to fall off below the glumes.

Timothy may be confused with reed canary grass (Phalaris arundinacea) early in flowering or one of our species of Alopecurus (among the grasses called foxtails), especially where timothy is growing in wetter areas. However, reed canary grass has larger and looser flowering heads, especially toward pollination time, and its glumes lack any bristles or awns. The flowering heads of Alopecurus are very similar to those of timothy, but the spikelets are not strongly flattened and are more or less ovate in outline. The glumes do have long hairs but they lack awns at the tip in Alopecurus and the lemmas have a delicate awn extending from the back. The glumes of timothy in contrast have strong awns and the lemmas lack awns entirely.

Etymology: Phleum from the Greek phleos referring to a reedy grass; pratense from the Latin pratensis meaning growing in meadows or pastures.

Plants perennial, tufted. Culms 20-120 cm tall, 2-5 mm in diameter, lowermost internodes frequently swollen and bulblike. Leaves with the sheaths open, smooth; ligules 2.5-3.5 mm, membranous; blades 9-30 cm long (flag leaves may be less than 9 cm long), 4-8 mm wide, flat. Flowering heads 2-15 cm long, 0.4-0.8 cm wide, densely cylindrical. Spikelets 3-4 mm long, 0.7-1.4 mm wide, U-shaped, strongly laterally compressed, with one floret; glumes subequal, 3-4 mm long, keels bristly-hairy, the tips appearing horned; lemmas 1.6-2 mm long, truncate at the tip. Chromosome number 2n = 42 (but different ploidy levels also known).