MSU Extension Floriculture & Greenhouse Crop Production

the most common and problematic broadleaf weeds in nurseries and greenhouses. It belongs to the Asteraceae family, which also includes dandelion, thistles and sunflower. It is classified as a winter annual because the seeds germinate in late fall through early spring. Sometimes common groundsel is considered a summer annual since it has the capacity to germinate under shady conditions in summer or fall. In addition to its general weediness, common groundsel can be toxic to cattle, swine and horses if ingested. The toxicity is due to pyrrolizidine alkaloids, which can cause chronic liver damage to these animals (Smith-Fiola and Gill, 2014; Uva et al., 1997).

The success of this weed lies with its ability to produce enormous amount of seeds. Seed development starts early in its life cycle and plants typically produce 1,700 seeds but can produce 25,000 or more seeds under optimal conditions (Wilen, 2006). Several races of common groundsel have developed resistance to triazine herbicides [atrazine and simazine (Princep)], as well as nitriles (bromoxynil) and uracils [terbacil (Sinbar)] (Smith-Fiola and Gill, 2014). In this bulletin, growers will learn how to identify and manage common groundsel in their nurseries and greenhouse operations.