A little purple in those leafs, hmmmmmm.

Sounds like goosegrass.

From http://www.msuturfweeds.net/details/_/goosegrass_50/

"Preemergence herbicides are most effective for controlling goosegrass infestations. Most annual grass preemergence herbicides are relatively effective on goosegrass, however, in areas where goosegrass replaces crabgrass as the primary annual grassy weed, applications should be delays two after optimum crabgrass application timing. Oxadiazon is the most effective preemergence for goosegrass control."

Have you applied a pre-emergent yet?

>" I tried killing it off with roundup last year, but that did not seem to work."

In order for Round Up (glyphosate) to work, the plant must be actively growing when the product is applied to its leaf tissue. Looks like another week or so and it will really be actively growing, depending on future soil temperatures.

Thanks Gary. I am pretty new at this (actually very inexperienced). So...no I have not applied a pre-emergent. What should I be looking for and when should I apply and where can I obtain? - thanks!

>" I am pretty new at this (actually very inexperienced)"

Not a problem at all. Like anything, experience comes with time.

>" What should I be looking for and when should I apply and where can I obtain?"

I'd recommend this to be applied soon ... ASAP (as soon as purchased)

http://www.acehardwareoutlet.com/%28lbhnt1yucgsr2g55fore5puq%29/ProductDetails.aspx?SKU=75086

http://doitbest.com/Pesticides-Scotts+Company-model-49805A-doitbest-sku-741380.dib

Then, once you have mowed a couple times, late April / early May, apply a straight fertilizer. Say - Turf Builder for example, will work.

Keep up with the weeds in spring. Use a general herbicide like Weed B Gone with Crab Grass Killer which does a VERY good job. I prefer the concentrate as it's more economical. I mix it in a 1 gallon plastic milk jug and spot spray as needed using a household Windex type sprayer. Then empty the sprayer back into the jug, rinse it out and done.

* Optional - Late June, apply GrubX as insurance.

During summer, fertilize yourself with nice BBQ, not the grass.
Do not kill weeds during the heat.
Only water deeply and mow tall.

Never cut more than 33% of the blades length when mowing. (if it grows to 6" tall, 4" tall is the shortest you can safely mow to) Yes, during spring this will means mowing twice a week. During summer, depending on the heat, it now may only be once every two weeks.

Labor Day, fertilize again, using the same stuff from May.
Mid October - repeat.
Thanksgiving - repeat for the last time and put it to bed. (this step provides the nitrogen to be stored, over winter, until the temps begin to rise again the next spring)

During fall - again stay with any weeds that pop up now with the cooler weather. Doing so in fall will prevent the winter annuals from popping up the following spring.

Finally, you need to read something, being a newbie. This is a copy and paste from a member here stresses the importance of mowing and watering and reinforces my mantra of "this aint rocket science" It really is as easy as:

"Always deep, infrequent watering. Your lawn needs one inch of water per week including rainfall. Using tuna cans placed in various places, run the sprinkler to obtain one inch of water in the tuna cans and time it. Run the sprinklers each week for that amount of time in every section to achieve one inch of irrigation all over. One inch will moisten the soil to a depth of 6-8 inches. This encourages the roots grow deeply. The soil will pull the water downward. The roots will grow down looking for water and nutrients. Each week, be sure to take rainfall into consideration.

Always mow high at 3 inches or higher on a regular basis. Mowing high permits proper photosynthesis. That means the grass needs sunlight to grow. The shorter the blades of grass, the more you impede the photosynthesis process. It is also very important to remember never to cut more than one third of the grass blade at a time. You may wish to mow once a week or 2-3 times a week depending on how fast the grass grows, just so long as no more than one third is cut off at once.

Infrequent deep watering and frequently mowing high are the two crucial points of lawn care. Anything else you do is secondary to these cultural practices. Proper watering and proper mowing are what encourage a healthy growing environment for a lush green lawn that is able to crowd out weeds.

I wouldn't worry about the condition of your lawn right now. Once you begin soil amendment, deep watering, mowing high, and de-weeding, it's going to look fantastic this summer. "