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Annual bluegrass, often called Poa annua, is a weed that can present itself during the growing season. It germinates in the cooler seasons, once the temperature drops below 70 degrees F, usually in late summer or early fall. It remains in a vegetative state through the winter and then produces seed during the spring and summer, at a high rate. One plant can produce more than 360 viable seeds. This grass grows well under cool conditions in grass that is mown short. 


Annual bluegrass is a lighter green colour than Kentucky bluegrass and other desirable lawn species. Thus it is often noticeable in lawns. Also the prolific seed heads are not visually pleasing.

Annual bluegrass - light colored weed grass in lawns

How can you prevent the growth of this weed?

Chemicals controls are  unlawful in some areas such as Ontario.

Annual bluegrass- is relatively easy to remove by pulling or digging- if done after a good rain - the roots will come out more easily.

Use these natural or cultural control methods to reduce the growth of annual bluegrass on your lawn.

 Water your lawn deeply and infrequently. Annual bluegrass thrives with overly moist soil, so be sure you are watering deep enough for your grass to soak up the moisture, but infrequently enough that the bluegrass will be less likely to germinate.

 Mow your lawn high and frequently. The weed grass seeds need light to germinate. If you keep your grass longer, it will block the light from the seeds of the bluegrass and reduces the amount of annual bluegrass in your lawn.

 Reduce soil compaction. Aerate the soil in your lawn to loosen the soil. Annual bluegrass can tolerate compacted soil. Aeration will help prevent the annual bluegrass from growing. Just be sure to avoid doing this during its germination season, because core aeration will encourage growth rather than inhibit it during germination.

 Over seed your lawn. Keep your lawn thick by planting new grass seeds each year to prevent the annual bluegrass seeds from growing in your lawn.

How can you prevent the growth of this weed?  Chemicals controls are  unlawful in some areas such as Ontario.


Also keep your lawn well supplied with nutrient enhancing lawn care program to keep it thick and full. A lawn with a thin stand of desirable grasses is more likely to become infested with annual bluegrass.


written by: cedricshaddy



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