I noticed this strip of green grass along someone's lawn on a curved part of the street. 
My guess is that this edge of the lawn has been fertilized by people walking their dogs. 
The dog urine has left that small narrow strip much greener than the rest of the lawn.

 If you have a lawn/tree/shrub that needs some Tender Loving Care- get The KING OF GREEN:

I passed this small plaza where the lawn is wall to wall dandelions. In the midst of the sea of yellow, were some patches of green that had no dandelions.

It looks like the only lawn care they get is some regular mowing.

I took a closer look- the patches of green are clumps of an thick bladed wild grass. Not a variety that most people would want on their front lawn.

The point though - is that this grass grows very dense. Dense enough that the dandelions were not able to grow where this grass is growing. This shows that having a healthier, thicker lawn is of value in keeping out weeds.

In the same boulevard, I found another patch with few weeds. The grass here was greener and denser than the surrounding weed infested lawn.

My guess is that this is a patch of lawn that was fertilized by that some neighborhood dogs.

 If you have a lawn/tree/shrub that needs some Tender Loving Care- get The KING OF GREEN:

Building up the soil.

Roots are the important part of the turf. The grass blades are what you see, they are what we enjoy. But if the roots are healthy, the top will be healthy.

And healthy roots depend on good soil conditions. Too often, new lawns are installed at new homes on very poor soil. The topsoil is stripped off, the foundations are dug. Then subsoil is moved around to grade the yards. There may be a little soil scattered under the sod. Often the soil has been trampled down by trucks and machinery, so that the soil is hard and compacted.

At a recent seminar, we learned that 3 things should be done to improve the lawn in these cases. (Although starting over is the best option, it may not be financially feasible)

1.  Aerate the lawn to help roots penetrate the hard packed soil beneath. Perhaps you've noticed the difference between dandelion roots and grass roots. Dandelion roots can penetrate pavement. Grass plants have fine textured roots that have a harder time breaking through hard soil.

2. Apply some phosphorous to the lawn. In established lawns, phosphorous is rarely needed. Once phosphorous is applied, it does not leach away. Established soils typically have good phosphorous levels. Root development is spurred by adequate phosphorous levels.

3. Increase the microbial population. Subsoils are devoid of all the bacteria that normally inhabit a healthy soil. The microbes need organic matter to be able to thrive. Adding organic matter is the best way to help establish a healthy microbial population. Organic matter can be added by topdressing with black soil, peat moss or by using composted dry materials such as our Top 'OM application.