Make sure you are getting at least 3hrs of sunlight and all sprinklers are covering the area so, lawn will grow thicker. Once you fix this...buy some seeds at home depot and it should get better..
i been in the lawn care business for 15 years...
hope that helps

15 years??? Some seeds????

The reason the lawn is thin near the pavement is the pavement holds the heat from the sun and dries the soil out all day and all night. You might consider something different or plan to water a little extra near the concrete.

What time of day are you watering? How long do you water? You should be watering about an inch at a time (measure with cat food or tuna cans). And you should only be watering once a month this time of year. And this would be a good place to mention that it would be much more helpful to tell us the town you live in. Zone 10 CA is not helpful at all. I'm guessing San Diego, but it could easily be Calexico where conditions are much different.

The close up pic is of bermuda grass. It does not look like the rest of the yard is bermuda. Bermuda likes different care from most other grasses. It really likes to be mowed at your mower's lowest setting. Fescue, your likely other grass type, likes to be mowed at the mower's highest setting. You can decide now which one you like more and just set your mower for that height. It will take care of itself for the most part. Fescue, however, will need to be reseeded in the fall if you want to thicken it up. It does not spread like bermuda grass.

If you are near the coast (really need to know) then Kentucky bluegrass makes an incredible lawn. You would have to start over but that is not that difficult. You would have all summer to think about that. I'll attach a pic of a KBG lawn near Long Beach.

Nothing will grow on the south side of the hedge you have out front. If you are going to leave that in, you should plant flowers or something on the north side of that.

The reason your back yard is bumpy is that someone in the past has rototilled the soil. They might have had a garden once. You can level that by adding sand to the holes. If you want to dig up the high spots, that becomes a lot more work.

Thank you thank you thank you for posting pictures. Now tell us where you live!

Here is some general lawn care best practices. These are not mine. In fact when I first started doing this, I disagreed with all of it, but by reading here over the years, these really (REALLY) do work. They are in order of importance.

1. Water deeply and infrequently. As I described above, water all at one time but not very often. Monthly in the cool months working your way up to every 7 days if you really get HOT. Don't fall for the plan of watering a little bit every day - even if your neighbors all do that. It is a recipe for disease and weeds.

2. Mulch mow at the mower's highest setting unless you have bermuda, bentgrass (you don't) or centipede (you don't).

3. If you are going to use chemical fertilizers, do the first app any time after you mow real grass for the second time in the spring. Fertilizing before that is a waste of fertilizer because your roots are not ready. A good starting schedule is Memorial Day, Labor Day, and Thanksgiving. If you are going to use organic fertilizer (look for the Organic Lawn Care FAQ on the FAQs of the GardenWeb Organic Gardening Forum), then you can fertilize any day of the year, or every day of the year, almost as much as you can afford. It is very hard to overdo organic fertilizer.

If you decide to go with bermuda, it can use chemical fertilizer every month. Bermuda is a nitrogen hog. Other grasses cannot tolerate chemical ferts in the summer.

KBG lawn in Huntington Beach. All he does is water infrequently, mow high, and occasionally fertilize with used coffee grounds.

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dchall_san_antonio, that's really nice lawn there!

Thank you for your replies, a lot of information for me!

We live in San Diego, about 12 mile "air distance" from the sea. My backyard has south exposure, full sun from morning to 5pm (hill blocks late afternoon sun). My front yard is to the north of the house and has a big tree and mild slope to the street.

Right now I'm watering both lawns 7:30am, twice a week with 7 minutes each. So do you suggest me to decrease the frequency and add some minutes?

Front lawn was original, back lawn was put down by the previous owner 3 years ago. Do you mean front lawn looks like a mix of Bermuda and Fescue? 4 months ago when gardener came to trim the bushes, they said the back lawn is Tall Fescue. They probably added same seeds to both lawns.

Is it necessary to aerate or to de-thatch?

Is there anyway to lower the border of my back lawn? It doesn't quite show in the following picture but when you stand on it you can really feel it is much denser at the edge.

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Thank you!

I'm going to ask again to narrow down where you live. San Diego is a cool season, coastal community. If you are 12 miles inland, you live in El Cajon or some place where the summer temps get up over 100 degrees. That makes a huge difference with turf grass. As you are well aware, the SoCal climate changes dramatically by driving a few miles.

Your new pic shows a Kentucky bluegrass turf that has some thatch. That is what you are describing as dense. Density is one of the advantages of KBG, but from what you say you are watering too frequently and it's getting thatchy. You can rent a dethatcher, vertical mower, power rake, verticutter, or slit seeder. These are all the same tool with vertically rotating blades that slice through the thatch. Your lawn will look horrible for a week but it will do what you want. Then yes, get off that 2x weekly watering, especially this time of year.

You'll need to transition off of your watering program. Try watering only once a week and see what the grass does. If you see any part of it dry out, water immediately but water for a longer time next time. Do not let the water run off. If you get run off, stop right away and let the moisture soak in for 30 minutes. Then resume until you get the time you want on it. If your soil seems to be hard and never softens, even after watering, that is another issue. Write back.

There are a couple of problems with frequent watering. One is that the soil never dries out. That means all the weed seeds on the soil are getting just the right amount of water to sprout. You don't want that. You want the soil surface to dry out completely between waterings. The roots will still be moist deeper down. The second problem is with disease. Many fungal diseases like the moisture. If you let it dry completely, you will forestall those particular diseases. The third problem with frequent watering and KBG is thatch, which you see in the picture and feel under foot. The fourth problem with frequent shallow watering is your roots will only grow very shallow leaving no drought tolerance. When you water deeper and less frequently, the roots will grow deeper into the soil to get at that deeper moisture. Deeper watering will help you with the thin grass near the pavement.

That KBG will be gorgeous once you get it watered, mowed, and fertilized correctly. The lawn I posted in my previous message is KBG so...same thing. KBG tends to go dormant (brown) in the winter but probably not in your area. If you keep it mowed up high (3 inches is great - no lower), then it should keep the bermuda at bay. Same in the front if you have any KBG out there.

This time I'm going to attach a pic of a zoysia lawn fertilized with alfalfa pellets (rabbit food). The picture was taken in June 2011, 1 month after the application. Note the change in color and density. I like to make the point with that picture that organic lawn care really works. Thanks to mrmumbles for posting it here last year.

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Your pix are fantastic! You'd be surprised how often we get pictures from a huge distance taken on an old cell phone with a greasy lens.

Impressive results with organic.

Thank you so much for your suggestions, they make sense to me.

I'm living in Rancho Bernardo area. And some summer days the temperature does go really high.

My front lawn does not hold water very well because of the slope and maybe some old soil. I'll take some measurements and see how much water it gets from the sprinkler, and how long before I have any runoff.

Rancho Bernardo. Jeeze. 15 yard penalty for misleading us. Are you facing the ocean (windward) or on the back side of the hills? I'm just kidding, but only slightly. On the windward side of the hills you can easily grow Kentucky bluegrass. On the back you'll have to watch the summer heat.

In the front you might have to adjust your sprinklers to put out less water. I have my oscillator sprinkler set to cover 900 square feet. It takes 8 full hours to accumulate an inch with my water pressure. That means I have great control over how much I water. One hour is 1/8 inch. Some sprinkler systems put out 1 inch in 15 minutes. Those suckers are hard to control and usually get runoff. If you have a timer you can do it by setting it for a few minutes, wait a few, add a few more, and repeat. But do it all on the same day or night.

You can soften your soil by spraying it with baby shampoo. I know that sounds crazy but it is working for lots of people in the forums. Spray about 4 ounces per 1,000 square feet and then water (an inch). That will wash the soap down into the soil. Then go until the next watering and do not spray with soap. But on the watering following that, repeat the soap. That should do it for the rest of the season and next season if you never let the soil dry all the way out (I mean deep). This works by letting the water penetrate deeper into the soil. There is more to it than that but I'm getting tired of typing.