What is the difference between Poa annua and Poa pratensis?

Both types of ryegrass look very similar, but they have completely different characteristics and roles in the lawn. Here's an overview of the key distinguishing features:

Poa pratensis - Meadow bluegrass: (desirable)

– bluish-green leaf color
– forms underground stolons (rhizomes)
– seeds that germinate very slowly
– ensures a dense, resilient turf
– blooms sparingly; flowers are usually pale purple
– relatively tolerant of drought
– Prone to rust in late summer/fall, depending on the variety; otherwise very healthy
– very hardy
– expressly desired on the lawn

Annual bluegrass - Annual bluegrass: (undesirable)

– light green leaves
– forms clumps; produces seed stalks year-round
– whitish flowers
– has only shallow roots and can be partially removed by hand
– prefers nutrient-rich, moist sites with a high nitrogen supply
– resistant to trampling and tolerant of deep cuts
– tends to get dry quickly
– can be mitigated through targeted irrigation strategies
– highly susceptible to fungal diseases (e.g., anthracnose, snow mold)
– does not like acidic soil
– Not wanted on the lawn

As you Annual bluegrass You'll find out how to here.