Question
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Followup To
Question -
I live in Lacey, Washington near Olympia.  Bentgrass has taken over approximately 30% of my front yard.  Lawn care companies want me to mow my yard short or as an alternative kill the grass and then hydroseed over the dead sod (in the fall).  Local sod farms say I should kill the grass (as early as April or May), remove the sod and then hydroseed or resod after adding better soil (currently I have clay).  My lawn is currently too bumpy to mow short without scalping.  What are your recommendations.

Thanks
Answer -
If I understand you correctly, then you have bentgrass (undesireable) growing in your other grass which is ?

If you have cool season grass like tall fescue, kentucky bluegrass, or perennial ryegrass, you can either sow seeds (hydroseeding or manual seeding) in spring or fall (fall being preferred). If you plan on sodding the areas then your window is a bit wider, but spring re-establishment is generally acceptable (seeding is better done in early fall).

Late april would be a good time to eradicate existing bent grass (use round-up) and remove the old dead sod after 7-10 days when you are sure it is dead. Then loosen the top 1-2" of soil and rake smooth. Spread a starter fertilizer (high in phosphorus) and then sod. Alternatively, hydroseed. Hydroseeding is probably better done in late summer/early fall (grass seedlings establish better at that time), but sodding can be done in spring with great success. Spring hydroseeding is not impossible either, however.

It is not enough to mow the bent grass low. I know this is the 'standard' advice to eradicate existing grass, but unfortunately it does not work well for brent. brent grass actually grow denser the closer your mow it (hence use on golf courses as 'green' grass). Instead use round-up, which is a non-selective herbicide, e.g. it kills everything green it comes in contact with. apply on a calm day and avoid spraying desireable lawn areas, bushes, trees and flowers. The material is taken up through the leaves only (e.g. not active in soil) and no residue is left in soil after it dries. Avoid cutting the grass a few days before and after applying.

You do not have to add new topsoil. Grass will grow in clay soils without problem. Just remember to loosen the top 1-2" of soil before sodding/seeding to ensure good soil/seed contact. also make sure you roll a sodded lawn with a landscapers roller (can be rented at equipment rental stores).

Question - Having approximately 25% of the lawn with bent grass, one very large patch (30 x 10) and several smaller areas, do you recommend replacing the entire area (1200 square feet) or replacing just areas affected.  Also - how do you control in the future - neighbors have bent grass and perhaps they are the source of my problem.

Thanks

Answer
I would just replace the infected spots/large area.

Dig a 1/2 foot wide trench between your nighbors and you in the shape of a V (or actually a checkmark). Make the edge of the trench against the neighbors straight up/down and the keep a 45 deg angle on the edge going towards your lawn. Fill in the trench with some light mulching material such as hay or leaves. nothing which packs down too heavily.

Bentgrass runners will try to jump the trench, but you can on a monthly basis go along the property line and with a shovel chop down along the vertical line to cut any runners. also inspect your grass along the property line to find any escapees.