Annual bluegrass / Poa annua weed infestation with thin turf patches

Poa annua

What's visible: All three photos show the same story: clumps of fine-bladed, bright lime-green grass growing in a distinct rosette/spreading pattern that is clearly a different texture and color than the surrounding darker perennial ryegrass. The close-up (photo 3) shows the classic Poa annua growth habit — a low, star-burst clump with narrow, boat-tipped blades and a slightly crinkled leaf surface, radiating outward from a central crown. The wide shot (photo 2) shows these clumps scattered in irregular patches across the lawn rather than following drainage or shade lines, ruling out dry spots. The first photo shows a dense clump actively competing with and displacing the ryegrass. This is not crabgrass (which has wider, flat blades and spreads in a finger pattern) and not nutsedge (which has stiff, triangular stems).

Why it's there: Poa annua (annual bluegrass) thrives in the Pacific Northwest's cool, wet springs — exactly the conditions in Gig Harbor, WA right now. It germinates prolifically in fall and early spring, and by May it has established clumps that are hard to miss. Your partial shade and the current 48°F soil temp create ideal conditions for it to outcompete perennial ryegrass, which prefers warmer soils. Because your ryegrass is a bunch-type grass that can't fill in bare spots on its own, each clump that sets seed this spring will create dozens more problem spots next year if not addressed now.