Setaria adhaerens – very rare and probably always ephemeral alien. Formerly occasionally recorded as a wool alien in the valley of river Vesdre, at least between 1929 and 1948 (as Setaria verticillata).
Most recent records seem to be associated with cereals. However, Setaria adhaerens is by far best known today from plant nurseries. It is one of the more typical introductions in containers with olive trees and palms from southern Europe (Hoste & al. 2009). It is possibly more or less naturalised locally.
Typical plants of Setaria adhaerens are readily distinguished from S. verticillata by the total absence of hairs on the margins of the leaf sheaths. Some specimens however are more or less intermediate (presence of some scattered hairs, even on plants with all other leaf sheaths completely glabrous!).
According to some authors (see for instance Rominger 2003) Setaria adhaerens should have strigose leaf surfaces (vs. scabrous leaf surfaces in S. verticillata). Indeed, some collections are characterised by scattered hairy leaf surfaces but others, with leaf sheath margins completely glabrous, have scabrous leaf surfaces. In addition to leaf sheath characters, Setaria adhaerens typically has a much shorter and more or less conical inflorescence (obviously widest at base) and its bristles are remarkably longer than in S. verticillata.
This plant might be poisonous
How to get rid of:
This plant is best controlled by eliminating the plant before it flowers. Since seeds can still mature even if the plant itself is killed, it is imperative to remove the plant from the area if there is any evidence of flowering.
Seeds are not long-lived, usually remaining viable for about one year. Therefore, controlling this weed before flowering will have a great impact on the size of the next year's population.
Start monitoring for seedlings in early fall and remove seedlings and plants as soon as possible. Monitoring should continue through early summer.