Bounty Ended with 500 reputation awarded by pnuts
4 Added link for better user experience
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That is annual bluegrass, Poa annua. It grows in lawns during the spring (and/or fall, depending on climate) and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass itself, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

Also, if you use PGRs (plant growth regulator), such as flurprimidolflurprimidol (a-(1-methylethyl)-a-[4-(trifluoromethoxy)-phenyl]-5-pyrimidinemethanol) which slows the growth of the Poa annua more than the growth of the perennial turf grasses, it give these good grasses a head start, as well as drastically reducing the Poa annua's ability to produce seed heads, which will lead to decreasing populations of this weed in lawns each year that this treatment is applied.

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That is annual bluegrass, Poa annua. It grows in lawns during the spring (and/or fall, depending on climate) and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass itself, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

Also, if you use PGRs (plant growth regulator), such as flurprimidol (a-(1-methylethyl)-a-[4-(trifluoromethoxy)-phenyl]-5-pyrimidinemethanol) which slows the growth of the Poa annua more than the growth of the perennial turf grasses, it give these good grasses a head start, as well as drastically reducing the Poa annua's ability to produce seed heads, which will lead to decreasing populations of this weed in lawns each year that this treatment is applied.

enter image description here

enter image description here

That is annual bluegrass, Poa annua. It grows in lawns during the spring (and/or fall, depending on climate) and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass itself, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

Also, if you use PGRs (plant growth regulator), such as flurprimidol (a-(1-methylethyl)-a-[4-(trifluoromethoxy)-phenyl]-5-pyrimidinemethanol) which slows the growth of the Poa annua more than the growth of the perennial turf grasses, it give these good grasses a head start, as well as drastically reducing the Poa annua's ability to produce seed heads, which will lead to decreasing populations of this weed in lawns each year that this treatment is applied.

enter image description here

enter image description here

    Bounty Ended with 50 reputation awarded by Community
3 How I missed that part I do not know. :)
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That is annual bluegrass, Poa annua. It grows in lawns during the spring (and/or fall, depending on climate) and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass itself, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

Also, if you use PGRs (plant growth regulator), such as flurprimidol (a-(1-methylethyl)-a-[4-(trifluoromethoxy)-phenyl]-5-pyrimidinemethanol) which slows the growth of the Poa annua more than the growth of the perennial turf grasses, it give these good grasses a head start, as well as drastically reducing the Poa annua's ability to produce seed heads, which will lead to decreasing populations of this weed in lawns each year that this treatment is applied.

enter image description here

enter image description here

That is annual bluegrass, Poa annua. It grows in lawns during the spring and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass itself, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

enter image description here

enter image description here

That is annual bluegrass, Poa annua. It grows in lawns during the spring (and/or fall, depending on climate) and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass itself, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

Also, if you use PGRs (plant growth regulator), such as flurprimidol (a-(1-methylethyl)-a-[4-(trifluoromethoxy)-phenyl]-5-pyrimidinemethanol) which slows the growth of the Poa annua more than the growth of the perennial turf grasses, it give these good grasses a head start, as well as drastically reducing the Poa annua's ability to produce seed heads, which will lead to decreasing populations of this weed in lawns each year that this treatment is applied.

enter image description here

enter image description here

2 deleted 3 characters in body
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That is annual bluegrass, Poa annua. It grows in lawns during the spring and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass its elfitself, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

enter image description here

enter image description here

That is annual bluegrass, Poa annua. It grows in lawns during the spring and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass its elf, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

enter image description here

enter image description here

That is annual bluegrass, Poa annua. It grows in lawns during the spring and causes some very nice lawns to thin out, as it grows very thick and chokes out the lawn grass. The problem with removing it is that this is a grass itself, so you cannot kill it with selective weed killer. This site gives good information on the management of the grass. Do not overwater your lawn, especially in shady areas. When you water the lawn, water deeply and infrequently, as this grass is a shallow rooted water addict. Do not overdo the fertilizer as that will give these a head start over the turf. Keep your soil loose, as this species likes compacted soil. Maintaining a thick, vigorous lawn will discourage the grass from spreading.

enter image description here

enter image description here

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