Question
I have 2 questions regarding lawns. I live in MA.

1. There are sections of my yard with very thin grass. Instead of removing all the grass and start over I just want apply grass seed to the thin areas. What's the best way to do this?

2. There is a section of the yard with no grass at all during the May-June period. However during the July-August time frame, heavy "grass" starts to grow. It's looks like grass with thick blades. In the fall it goes away and start again the next year. Is this weed? If so how if I plant grass there will it take care of the problem?  

Answer
1. Best result is had if you loose the bare soil with a rake or machinery and then spread grass seeds thickly. Firm down with the back of a rake to ensure good soil/seed contact. If possible topdress (spread a thin layer, maybe 1/4") with compost before firming down. Water consistently, never allowing the top 1" of soil to dry out, for the first 7-28 days until grass has sprouted and is growing well.

2. You probably have a warm season grass which is not suitable for your area. My guess is either Bermuda or Zoysia (I think it is probably the latter). This type of grass is suited for the South, but not for northern states of the USA where it remains dormant (brown/crisp/gray) during the early spring and early fall. Not until soil temperatures go up, does it start to grow. When soil temperatures go down in fall, it will go dormant for the winter. It is excellent grass, but not very suited to northern areas due to the limited growing period.

The only way to combat this is to remove it completely and establish new grass. This should be done in early spring or early fall. Do not try to establish cool season grass (such as ryegrass or fescues) in mid summer.

The warm season grass is best capable of handling temperatures in summer and therefore it can be hard to eradicate then. Rent a sod cutter (or use a flat bladed spade) and sever roots. Set it deeply. Then spread grass seeds and water as 1. above. You can also use a contact herbicide (Round-Up) to eradicate the warm season grass. Best time to eradicate is early fall at which time you can a) make sure the warm season grass has been completely eradicated, and b) the cool season grass sprout fast.

It is important to eradicate the warm season grass entirely before starting or you get a strange mix which is difficult to control later.