Question
I have a weed in my yard that grows where the grass doesn't grow well under my pecan tree.  It is very flat, low lying, vines, and produces a three pronged sticker that I am sure is the seed.  When the flat little green leaves die away in the winter, there is only a ball of these stickers left.  I have searched and searched and can not determine exactly what it is called.  Looks like a dollar weed, but I don't think that is what it is.  I have gone organic since last summer, but it probably will be easier to kill it pre-emergent if I can.  Not sure what to use.  Corn gluten meal?  I used vinegar and orange oil on it in the heat of the summer last year and it would kill the leaves, but they just kept coming back.  

So, Do I need to use corn gluten meal after tilling the area?  OR don't till it since that will bury the stickery seeds?  We actually covered it with a heavy tarp used on semi trailers towards the end of the summer last year, and i peaked under there today.  everything is currently dead, but still the sitckers lived.  I hate them so much I even took a vaccuum to the lawn today in an effort to get rid of them.  I NEED HELP!
Any thing you have is very, very appreciated.  

Thank you,
Lori

I can get pics of the little stickers if you need them.

Answer
Lori,

Any plant that is not grass in a turf area is considered by most as a weed.  Some plants such as clover are actually beneficial.  Even a dandelion with its long tap root is able to mine calcium from deep in the soil making it available to the turf.

In any instance the weed is also an excellent way to help identify problems with the soil.  Compaction, nutrient and mineral deficiency, once resolved the weed no longer likes to live there.

A picture is a must.

Also consider a soil test if you have not already done so.