Poa annua

Poa annua is an annual grass weed from the large Poa family that tends to act as a perennial plant in irrigated situations. This species which is sometimes referred to as “annual winter grass” or “green-keepers curse” is endemic in soils throughout temperate parts of the world. It is a relatively small grass plant which is light green to yellow green in coloration and it produces clusters of small white prolifically, throughout the year.

The leaf blades are soft and often crinkled when young. Poa annua is often confused with poa trivialis which is a perennial grass from the same family but is distinguishable by having bright green, shiny leaves. Poa annua seeds prolifically and will seed regardless of cutting height. It is probably the most common grass weed problem for lawns in New Zealand.  

Typically, it will germinate in the absence of competition so is most prevalent on newly established lawns. In the absence of irrigation the plants will die out during the hotter summer months and these plants will not re-emerge. However, in irrigated situations poa annua can behave and persist much in the same manner as a perennial plant. When it behaves in this manner it can be hard to eradicate from temperate grass lawns and several treatments may be required.