Giant foxtail a.k.a. Japanese bristlegrass, Joncaire Street, 6 August 2026 (photo by Kate St. John)

11 August 2026

On a walk last week on Joncaire Street near Schenley Park I was struck by the size and diversity of the weeds by the sidewalk, especially the grasses.

Why look at weeds?

Peter Del Tredici explains in Wild Urban Plants of the Northeast that cities have become novel (“new”) ecosystems. We have a mix of natives and aliens, never seen before, that survive and even thrive in the cities’ microhabitats. Weeds are the thrivers so they’re worth a look.

One thriver I did not notice at Joncaire — I probably ignored it — is green foxtail (Setaria viridis) or green brittlegrass. It grows everywhere in disturbed soil, vacant lots, the cracks in sidewalks, in lawns and along roads. According to Wikipedia it is very common and the wild antecedent of the crop foxtail millet. I’ve seen birds eat it when the seeds are ripe.

Green foxtail (Setaria viridis) is a common roadside grass (photo from Wikimedia Commons)

Green foxtail has a completely green head. Both photos are from Wikimedia.

A little less common that the green one are yellow foxtail and giant foxtail, both at Joncaire.

Yellow foxtail or yellow bristlegrass (Setaria pumila) has upright heads like green foxtail but the seeds are yellowish and there are red flower parts (?stamens?) protruding from the head.

Yellow foxtail, Joncaire Street, 8 August 2026 (photo by Kate St. John)

Yellow foxtail at Joncaire Street, 6 August 2026 (photo by Kate St. John)

The giant foxtail (Setaria faberi) a.k.a. Japanese brittlegrass stood out on Joncaire because the plants were almost over my head. This alien from Asia is pictured at top on Joncaire Street and below from Wikimedia.

Giant foxtail / Japanese brittlegrass (photo from Wikimedia)

Grasses are annuals that dry out at the end of the growing season. When foxtail invades the wildlands in the West it is dangerous fuel in wildfire season.

Fortunately we are not in fire danger in western PA. Today we are under a Flood Watch.