What type of weed is characterized by spiny, notched leaves and typically occurs when turf is mowed?

Thistles are perennial weeds known for their distinctive spiny leaves that often have a notched appearance, making them easily identifiable in turfgrass areas. These characteristics allow them to stand out as they emerge among the grasses. Thistles thrive in disturbed soils and can often be found in lawns that have been recently mowed, as the mowing can create the ideal conditions for their growth due to reduced competition from other vegetation. The resilience of thistles allows them to grow back vigorously, often producing flowers that can further contribute to their spread.

In contrast, violets typically have broad, heart-shaped leaves and may not have the spiny, notched characteristics of thistles. Common chickweed features opposite leaves that are smooth and not spiny, and it usually grows in more moist, shaded areas rather than being predominant after mowing. Ground ivy, while having a creeping growth habit, has kidney-shaped leaves with a distinct shape and does not fit the description of being characterized by spiny, notched leaves. Therefore, thistles are the correct identification based on their specific leaf characteristics and growth behavior in turfgrass.