Which of the following is an indicator of compacted soil?

• A. Dandelion
• B. Prostrate knotweed
• C. Crabgrass
• D. Vetch

Answer: (B)

When soil is compacted, air and water movement are restricted and roots can’t penetrate easily. In turf and landscape management, certain weeds thrive under these tighter soil conditions, so their presence helps signal compaction. Prostrate knotweed grows low and forms spreading mats, and it tends to dominate in areas with hard, compacted soil or poor drainage. Finding this weed indicates the soil structure is likely compacted and deserves relief, typically through aeration and improved drainage. Other weeds like dandelion can tolerate hard soil because of their deep taproots, but they’re more a sign of disturbed or bare patches than a specific indicator of compaction. Crabgrass appears in stressed, thin turf and isn’t a reliable marker of compaction alone, and vetch indicates nitrogen-rich, well-drained conditions rather than compacted soil.